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Applied Surface Science (v.254, #22)

Surface reactions in atomic layer deposition of HfO₂, ZrO₂ and Al₂O₃ on hydroxylated and sulfur-passivated GaAs(100) surfaces: A comparative study by density functional theory by Jie Ren; Guangfen Zhou; Yongqi Hu; Haichao Jiang; David Wei Zhang (pp. 7115-7121).

The surface reactions in atomic layer deposition (ALD) of HfO₂, ZrO₂ and Al₂O₃ on hydroxylated and sulfur-passivated GaAs surfaces are compared by using density functional theory. The HfCl₄ and ZrCl₄ half-reactions show large similarities in energetics and geometrical structure. However, both of them show large discrepancies with the Al(CH₃)₃ (TMA) half-reaction. Calculations find that it is more energetically favorable for the Al₂O₃ deposition than the HfO₂ and ZrO₂ deposition at the initial ALD stage. In addition, calculations find that although the GaAs passivation with sulfur helps to improve the interfacial properties, it is both kinetically and thermodynamically less favorable.

Keywords: Density functional theory; Dielectrics; Gallium arsenide; Atomic layer deposition

Optical properties of GaInNAsSb/GaAs/GaAs1−_xN_x ( x≈10%) saturable absorber quantum wells by S. Ben Bouzid; W. Zaghdoudi; A. Hamdouni; N. Ben Sedrine; F. Bousbih; J.C. Harmand; R. Chtourou (pp. 7122-7126).

We study the effect of the GaAsN narrow QWs on the optical properties of the GaInNAsSb/GaAs QWs using photoluminescence spectroscopy. A drastic effect of the N-rich layers on the QW photoluminesecnec (PL) intensity was observed with a strong influence of the spacer thickness. In the PL spectra a broad band caused by excitonic transitions related with N-related clusters in GaAs barriers is found. Based on calculations from experimental data, we have identified the low QW peak energy to the E₁–H₁ transition using the shear deformation potentials report Δ p/ p=0.24.

Keywords: GaInNAsSb; GaAsN; Molecular beam epitaxy; Semiconductor saturable absorber

XPS study of five fluorinated compounds deposited on calcarenite stone by Alberto Torrisi (pp. 7127-7136).

This paper reports the results of XPS study of the chemical modifications that occurs at the surface of five fluorinated compounds, deposited on calcarenite specimens, after 240h of a simulated ageing in a climatic chamber under UV radiation and thermal stress. It has been found that the modifications occurred after this ageing treatment are not dramatic, nevertheless they are revealed by XPS analysis. However, these modifications do not affect the values of the static contact angles which remains practically unchanged after the ageing treatment with respect to those obtained before.

Keywords: XPS; Protective; Calcarenite

Effect of surface physicochemical properties on the lubricating properties of water film by Shuhai Liu; Jianbin Luo; Gang Li; Chenhui Zhang; Xinchun Lu (pp. 7137-7142).

Effect of surface physicochemical properties on the water film confined within a nanogap was investigated. The film thickness and friction force were measured by the Relative Optical Interference Intensity (ROII) method and a UMT-2MT tribotester. It was found that the confined water film formed the thicker lubricate film than the prediction of elastic–isoviscous lubrication theory. Experimental results indicate that the higher the solid/water interfacial energy is, the thicker lubricate film the highly viscous “interphase” water layer forms and the lower the friction force is.

Keywords: Water film; Water lubrication; Interfacial energy; Film-forming mechanism

MAPLE deposition of biomaterial multilayers by Valeria Califano; Francesco Bloisi; Luciano R.M. Vicari; Paolo Colombi; Elza Bontempi; Laura E. Depero (pp. 7143-7148).

Double layers of polyethylene glycol (PEG) and 3-(3,4-dihydroxyphenyl)-2-methyl-l-alanine (m-DOPA) thin films were obtained by matrix assisted pulsed laser evaporation (MAPLE) technique, by depositing a first layer of m-DOPA on Si substrate and a second layer of PEG on top of it. The films were characterized by low angle X-ray diffraction (LAXRD), X-ray reflectivity (XRR), atomic force microscopy (AFM), and micro-Raman spectroscopy. From these analyses it resulted that PEG was deposited without any relevant damage both in terms of chemical structure and molecular weight. Furthermore, PEG chains were mostly in the extended conformation, although PEG micelles appeared.

Keywords: PACS; 61.10.Eq; 62.35.Gh; 68.37.Ps; 68.55.−a; 81.15.FgMAPLE; Surface morphology; Thin films; Polyethylene glycol

High-temperature oxidation resistant (Cr, Al)N films synthesized using pulsed bias arc ion plating by Min Zhang; Guoqiang Lin; Guoying Lu; Chuang Dong; Kwang Ho Kim (pp. 7149-7154).

(Cr, Al)N films were deposited by pulsed bias arc ion plating on HSS and 316L stainless steel substrates. With pulsed substrate bias ranging from −100V to −500V, the effect of pulsed bias on film composition, phase structure, deposition rate and mechanical properties was investigated by EDX, XRD, SEM, nanoindentation and scratch measurements. The high-temperature (up to 900°C) oxidation resistance of the films was also evaluated. The results show that Al contents and deposition rates decrease with increasing pulsed bias and the ratio of (Cr+Al)/N is almost constant at 0.95. The as-deposited (Cr, Al)N films crystallize in the pseudo-binary (Cr, Al)N and Al phases. The film hardness increases with increasing bias and reaches the maximum 21.5GPa at −500V. The films deposited at −500V exhibit a high adhesion force, about 70N, and more interestingly good oxidation resistance when annealed in air at 900°C for 10h.

Keywords: Arc ion plating; Pulsed bias; (Cr, Al)N films; High-temperature oxidation resistance

Phase transition and magnetic properties of Mg-doped hexagonal close-packed Ni nanoparticles by Jinghai Yang; Bo Feng; Yang Liu; Yongjun Zhang; Lili Yang; Yaxin Wang; Maobin Wei; Jihui Lang; Dandan Wang; Xiaoyan Liu (pp. 7155-7158).

Mg-doped Ni nanoparticles with the hexagonal close-packed (hcp) and face-centered cubic (fcc) structure have been synthesized by sol–gel method sintered at different temperatures in argon atmosphere. The sintering temperature played an important role in the control of the crystalline phase and the particle size. The pure hcp Mg-doped Ni nanoparticles with average particle size of 6.0nm were obtained at 320°C. The results indicated that the transition from the hcp to the fcc phase occurred in the temperature range between 320°C and 450°C. Moreover, the VSM results showed that the hcp Mg-doped Ni nanoparticles had unique ferromagnetic and superparamagnetic behavior. The unsaturation even at 5000Oe is one of the superparamagnetic characteristics due to the small particle size. From the ZFC and FC curves, the blocking temperature T_B of the hcp sample (6.0nm) was estimated to be 10K. The blocking temperature was related to the size of the magnetic particles and the magnetocrystalline anisotropy constant. By theoretical calculation, the deduced particle size was 6.59nm for hcp Mg-doped Ni nanoparticles which was in agreement with the results of XRD and TEM.

Keywords: PACS; 61.46.Df 75.75. +aNanostructures; Chemical synthesis; Magnetic properties; Phase transitions

Electron beam physical vapor deposition of YSZ electrolyte coatings for SOFCs by Xiaodong He; Bin Meng; Yue Sun; Bochao Liu; Mingwei Li (pp. 7159-7164).

YSZ electrolyte coatings were prepared by electron beam physical vapor deposition (EB-PVD) at a high deposition rate of up to 1μm/min. The YSZ coating consisted of a single cubic phase and no phase transformation occurred after annealing treatment at 1000°C. A typical columnar structure was observed in this coating by SEM and feather-like characteristics appeared in every columnar grain. In columnar grain boundaries there were many micron-sized gaps and pores. In TEM image, many white lines were found, originating from the alignment of nanopores existing within feather-like columnar grains. The element distribution along the cross-section of the coating was homogeneous except Zr with a slight gradient. The coating exhibited a characteristic anisotropic behavior in electrical conductivity. In the direction perpendicular to coating surface the electrical conductivity was remarkably higher than that in the direction parallel to coating surface. This mainly attributed to the typical columnar structure for EB-PVD coating and the existence of many grain boundaries along the direction parallel to coating surface. For as-deposited coating, the gas permeability coefficient of 9.78×10⁻⁵cm⁴N⁻¹s⁻¹ was obtained and this value was close to the critical value of YSZ electrolyte layer required for solid oxide fuel cell (SOFC) operation.

Keywords: PACS; 76.61−.rEB-PVD; YSZ electrolyte coatings; SOFC; Electrical conductivity

Surface modification of activated carbons for CO₂ capture by C. Pevida; M.G. Plaza; B. Arias; J. Fermoso; F. Rubiera; J.J. Pis (pp. 7165-7172).

The reduction of anthropogenic CO₂ emissions to address the consequences of climate change is a matter of concern for all developed countries. In the short term, one of the most viable options for reducing carbon emissions is to capture and store CO₂ at large stationary sources. Adsorption with solid sorbents is one of the most promising options. In this work, two series of materials were prepared from two commercial activated carbons, C and R, by heat treatment with gaseous ammonia at temperatures in the 200–800°C range. The aim was to improve the selectivity and capacity of the sorbents to capture CO₂, by introducing basic nitrogen-functionalities into the carbons. The sorbents were characterised in terms of texture and chemical composition. Their surface chemistry was studied through temperature-programmed desorption tests and X-ray photoelectron spectroscopy. The capture performance of the carbons was evaluated by using a thermogravimetric analyser to record mass uptakes by the samples when exposed to a CO₂ atmosphere.

Keywords: Activated carbon; Surface modification; Thermal analysis; CO; ₂; capture; Adsorption

XPS study of laser fabricated titanium/KaptonFN interfaces by Grigor L. Georgiev; Taslema Sultana; Ronald J. Baird; Gregory Auner; Golam Newaz; Rahul Patwa; Hans Herfurth (pp. 7173-7177).

KaptonFN film consists of a polyimide core that has been laminated with FEP fluoropolymer outer layers. This composite material's resistance to most chemical solvents, heat sealability and low moisture uptake make KaptonFN attractive as a packaging material for electronics and implantable devices. KaptonFN/Ti micro-joints were fabricated by using focused infrared laser irradiation. The micro-joints were mechanically debonded, and the KaptonFN/Ti interfaces were studied by using X-ray photoelectron spectroscopy (XPS). The locus of failure of the joints was found to be in the FEP layer near the interface with the Ti. The XPS results give evidence for the formation of TiF bond in the interfacial region.

Keywords: KaptonFN/Ti interfaces; Laser fabrication; XPS

Effect of annealing on the properties of N-doped ZnO films deposited by RF magnetron sputtering by Jinzhong Wang; Elangovan Elamurugu; Vincent Sallet; François Jomard; Alain Lusson; Ana M. Botelho do Rego; Pedro Barquinha; Gonçalo Gonçalves; Rodrigo Martins; Elvira Fortunato (pp. 7178-7182).

N-doped ZnO films were deposited by RF magnetron sputtering in N₂/Ar gas mixture and were post-annealed at different temperatures ( T_a) ranging from 400 to 800°C in O₂ gas at atmospheric pressure. The as-deposited and post-annealed films were characterized by their structural (XRD), compositional (SIMS, XPS), optical (UV–vis–NIR spectrometry), electrical (Hall measurements), and optoelectronic properties (PL spectra). The XRD results authenticate the improvement of crystallinity following post-annealing. The weak intensity of the (002) reflection obtained for the as-deposited N-doped ZnO films was increased with the increasing T_a to become the preferred orientation at higher T_a (800°C). The amount of N-concentration and the chemical states of N element in ZnO films were changed with the T_a, especially above 400°C. The average visible transmittance (400–800nm) of the as-deposited films (26%) was increased with the increasing T_a to reach a maximum of 75% at 600°C but then decreased. In the PL spectra, A⁰X emission at 3.321eV was observed for T_a=400°C besides the main D⁰X emission. The intensity of the A⁰X emission was decreased with the increasing T_a whereas D⁰X emission became sharper and more optical emission centers were observed when T_a is increased above 400°C.

Keywords: ZnO thin films; SIMS depth profiling; XPS analysis; PL spectra

Total electron yield XANES of zinc-blende MnTe by R.J. Iwanowski; E. Welter; E. Janik (pp. 7183-7186).

The electronic structure and chemical bond of zinc-blende (zb) MnTe have been studied by using total-electron-yield (TEY) X-ray absorption near-edge structure (XANES) spectroscopy. Close resemblances of the shape of Mn K-edge XANES in zb-MnTe and in Zn1−_xMn_xTe [A. Titov, X. Biquard, D. Halley, S. Kuroda, E. Bellet-Amalric, H. Mariette, J. Cibert, A.E. Merad, G. Merad, M.B. Kanoun, E. Kulatov, Yu.A. Uspenskii, Phys. Rev. B 72 (2005) 115209] indicated predominant influence of the 1st coordination shell. In particular, identical single-peak pre-edge structure for both cases was mainly ascribed to the Mn 1s-3d/4p weakly allowed dipole transitions. The quantitative analysis of XANES in zb-MnTe concerned the observed chemical shift of Mn K-edge threshold energy and a magnitude of the relevant cation–anion charge transfer (or effective cation charge), q(Mn–Te) [calculated after M. Kitamura, H. Chen, J. Phys. Chem. Solids 52 (1991) 731]. It also provided a comparison with our earlier X-ray absorption studies of Zn1−_xMn_xB alloys (B=S, Se). The estimated charge transfer within the chemical bond of zb-MnTe enabled us to complete the q(Mn–B) versus chalcogen ligand (B=S, Se, Te) dependence and to interpret it in terms of p-d hybridization and a contribution of Mn 3d electrons to the overall charge transfer.

Keywords: PACS; 61.05.cj; 61.50.Lt; 71.20.Be; 78.70.DmTransition metal compounds; NEXAFS; Crystal binding; Synchrotron radiation

Theoretical evaluation of the effective work functions for positive-ionic and electronic emissions from polycrystalline metal surfaces by Hiroyuki Kawano (pp. 7187-7192).

Effective work functions ( φ⁺ and φ^e) for positive-ionic and electronic emissions from polycrystalline metals of Nb, Mo, Ta, W and Ir are calculated according to our theoretical model by using those published data on both fractional surface area ( F_i) and local work function ( φ_i) of each metal surface composed of several patchy faces (1, 2, …, i). Comparison between the theoretical values thus obtained and those experimental data published to date yields the conclusions as follows. (1) With a slight error of less than ∼0.1eV, the value of φ^e calculated with each of the metals is in fair or good agreement with that determined by experiment. (2) Such agreement is found also with φ⁺ for W. (3) In a typical case of W, where the degree of monocrystallization ( δ_m) corresponding to the largest among the values of F_i is less than ∼0.5, the thermionic contrast (Δ φ*≡ φ⁺− φ^e) is found again to be nearly equal to both theoretical and experimental values reported previously. (4) Each of the five metals shows that Δ φ* at δ_m=0.68–0.95 is smaller than Δ φ* at δ_m<0.5. (5) This result strongly supports our theoretical prediction that Δ φ* decreases gradually to zero as δ_m increases beyond ∼0.5 up to ∼1. (6) Particularly, such a surface which has δ_m≥0.96 exhibits Δ φ*≈0, apparently equivalent to the so-called “monocrystalline surface ( δ_m=1)”. These results lead to the conclusion that our theoretical model is valid for evaluating the effective work functions probably with a slight error of less than ∼0.1eV, irrespective of both the surface species and the range of δ_m. In addition, our simple model makes it possible to analyze the mechanism of change in φ⁺ and φ^e according to the change in surface characters of both φ_i and F_i.

Keywords: PACS; 73.30.+yEffective work function; Local work function; Positive ion emission; Electron emission; Monocrystallization degree

Optical properties of La₂O₃ doped diamond-like carbon films by Zhenyu Zhang; Fengwei Huo; Zhenyuan Jia; Dongming Guo; Zhuji Jin; Renke Kang (pp. 7193-7197).

A novel kind of La₂O₃ doped diamond-like carbon (DLC) films with thickness of 100–120nm were deposited by unbalanced magnetron sputtering. Raman spectra and photoluminescence properties were measured by Raman spectrometer operated by 325nm He-Cd laser and 514nm Ar⁺ laser, respectively. The intensities of Raman spectra and photoluminescence are higher than those of pure DLC films. The La₂O₃ doped DLC films have the potential promising for the application of solar cell coatings.

Keywords: La; ₂; O; ₃; DLC; Photoluminescence; Unbalanced magnetron sputtering

On the combined use of scratch tests and CLA profilometry for the characterization of polyester powder coatings: Influence of scratch load and speed by M. Barletta; A. Gisario; L. Lusvarghi; G. Bolelli; G. Rubino (pp. 7198-7214).

The prediction of the mechanical properties of polyester powder coatings is of paramount importance, as they have to undergo a wide variety of forces and deformations during their service life. Determine the response of polymeric coatings to the actual loading conditions can be, however, very troublesome as their properties are function of the material physical state, rate-dependence and yield and break behaviour. Further, the characterization of soft, contaminated organic surfaces such as polymers can often cause severe problems with reliability and imaging accuracy due to instrumental artefacts.This is therefore the context in which this paper investigates the capability of multiple parameters scratch tests joined with non-contact CLA profilometry and FE-SEM to detect the scratch response of polyester powder coatings for protective and decorative outdoor applications. Scratch tests with blunt contact geometry were used to evaluate the response of polyester coatings baked at different time–temperature programs and, so, at different stages of their curing process. In particular, being such coatings highly non-linear in their response to mechanical stress or strain, the influence from scratch load and speed was carefully taken into account. Analytical evaluations of the experimental results led to good correlations between the extent of the deformed zone after scratch, scratch parameters and curing operational settings. This allows mapping the scratch response of the polyester topcoats to broad ranges of both scratch parameters and curing conditions.

Keywords: Polyester powder coatings; Multiple parameters scratch test; Scratch load; Scratch speed; Deformation response; Mapping; CLA profilometry; FE-SEM

CdS–ZnO composite nanorods: Synthesis, characterization and application for photocatalytic degradation of 3,4-dihydroxy benzoic acid by J. Nayak; S.N. Sahu; J. Kasuya; S. Nozaki (pp. 7215-7218).

Well-aligned arrays of CdS–ZnO composite nanorods were grown on indium tin oxide substrates. ZnO nanorods, deposited by a low temperature aqueous chemical growth technique, were dip coated with CdS. The CdS–ZnO nanorods were polycrystalline as confirmed from the low angle X-rays diffraction study. Photon to current conversion efficiency of CdS–ZnO composite nanorod was observed to be higher than that of CdS. In the micro-Raman spectrum, we observed longitudinal optical modes of CdS and ZnO showing their co-existence. The appealing application of CdS–ZnO nanorod as a visible photocatalyst was demonstrated and the possible mechanism was discussed.

Keywords: Nanorods; Seed layer; Photocatalysis; Benzoic acid

Formation of aligned silicon-nanowire on silicon in aqueous HF/(AgNO₃+Na₂S₂O₈) solution by R. Douani; T. Hadjersi; R. Boukherroub; L. Adour; A. Manseri (pp. 7219-7222).

Highly oriented silicon nanowire (SiNW) layer was fabricated by etching Si substrate in HF/(AgNO₃+Na₂S₂O₈) solution at 50°C. The morphology and the photoluminescence (PL) of the etched layer as a function of Na₂S₂O₈ concentration were studied. The SiNW layers formed on silicon were investigated by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). It was demonstrated that the morphology of the etched layers depends on the Na₂S₂O₈ concentration. Room-temperature photoluminescence (PL) from etched layer was observed. It was found that the utilisation of Na₂S₂O₈ decreases PL peak intensity. Finally, a discussion on the formation process of the silicon nanowires is presented.

Keywords: PACS; 62.23.Hj; 68.37.Hk; 81.65.cf; 82.45.jnNanostructures; Silicon nanowires; Electroless etching

Investigation of an efficient YbF₃/Al cathode for tris-(8-hydroxyquinoline)aluminum-based small molecular organic light-emitting diodes by Yang Li; Lian Duan; Qian Liu; Rui Zhang; Deqiang Zhang; Liduo Wang; Juan Qiao; Yong Qiu (pp. 7223-7226).

Efficient tris-(8-hydroxyquinoline)aluminum (Alq₃)-based organic light-emitting diodes (OLEDs) using YbF₃ as the electron injection layer have been investigated. With an YbF₃ (3.0nm)/Al cathode, the device with Alq₃ as the emitting layer achieved a better performance than the control device with a LiF (0.5nm)/Al cathode. The release of the low-work-function metal Yb is responsible for the performance enhancement. From the analysis by atomic force spectroscopy and X-ray photoemission spectroscopy, it is observed that the Alq₃-cathode interface could be well covered by YbF₃ at an optimum thickness of 3.0nm, which helps to prevent the contact between Alq₃ and Al, and to reduce the destruction of Alq₃ by Al.

Keywords: PACS; 85.60.Jb; 85.30.MnOrganic light-emitting diodes (OLEDs); Electron injection interface; Ytterbium(III) fluoride; Aluminum cathode

The interfacial structure of plated copper alloy resistance spot welded joint by Jingwei Wu; Guofu Zhai; Qing Chen; Jianqi Wang; Gang Ren (pp. 7227-7231).

Plated copper alloys are widely used in electron industry. The plating lay caused the farther decreasing of the welding property of copper alloys, whose intrinsic weldability was poor. In this paper, the bronze and brass specimens with nickel–tin double plating layer were joined by resistance spot welding method. The microstructure and peel strength of the joints were investigated. The experiment results show that a sandwich-like structure was obtained in the faying surface after welding, and the nickel plating layer thickness had severe effect on the reliability of the joints.

Keywords: Copper alloy; Resistance spot welding; Nickel–tin double plating layer; Peel strength

The tribological chemistry of polysulfides in mineral oil and synthetic diester by Jing Li; Haibing Ma; Tianhui Ren; Yidong Zhao; Lei Zheng; Chenyan Ma; Yong Han (pp. 7232-7236).

Two organic polysulfides, dipropyl trisulfide (DPTS) and 3,5-diisopropyl-1,2,4-trithiolane (DIPTT) in mineral oil (MO) and synthetic diester (DE) were investigated on thermal films and tribofilms by using X-ray absorption near edge structure (XANES) spectroscopy. The results of surface analysis reveal that the thermal films formed from MO for two additives are consist of sulfate and sulfite, while the distinct composition of the films from DE implies the different sensitivity to oxygen between two compounds. As to the tribofilms, “hydrosulfite-like compound” is differentiated from sulfite and FeS_x (1< x<2) is detected in low energy region from DPTS/MO, as well as a lower concentration of DPTS/DE. At a high concentration in DE, the surface of sample for DPTS is full of iron sulfide. With regard to DIPTT, iron sulfite is the exclusive oxidized form of sulfur instead of “hydrosulfite-like compound” in the tribofilms, which is an evidence suggesting a mechanism involving a role played by a thiyl radical.

Keywords: Polysulfide; Mineral oil; Synthetic diester; XANES; Thiyl radical

Molecular assembly and photophysical properties of Langmuir–Blodgett films with novel lanthanide complexes of long chain para-dodecanoyl and para-myristoyl oxybenzoate by Bing Yan; Bing Xu (pp. 7237-7242).

Several ultrathin luminescent Langmuir–Blodgett (LB) films have been prepared by using the subphase containing the rare earth ions (Eu³⁺, Dy³⁺). The effect of the rare earth ions on the monolayer of p-dodecanoyloxybenzoate (12-OBA) and p-myristoyloxybenzoate (14-OBA) was investigated. IR spectra showed the rare earth ions were bound to the carboxylic acid head groups and the coordination took place between the polar head group and the rare earth ions. The layer structure of the LB films was demonstrated by low-angle X-ray diffraction. The AFM study revealed that the LB films were uniform and crack free, and the films mainly consisted of closely packed grains with an average size of 241nm. The LB films can give off strong fluorescence, and the signal can be detected from a single layer. The characteristic luminescence behaviors of LB films have been discussed compared with those of the complexes.

Keywords: Langmuir–Blodgett film; Anthanide complex; Long chain carboxyphenol ester; Photophysical property

Fabrication of micro-structure on glass surface using micro-indentation and wet etching process by Yasuhiro Saito; Shinya Okamoto; Atsushi Miki; Hiroyuki Inomata; Takeshi Hidaka; Hiroaki Kasai (pp. 7243-7249).

In order to improve the new micro-fabrication technology using micro-indentation and wet etching, in which the etching rate drastically decrease at the indented area and consequently micro-structure can be formed on the glass surface, the effect of the applying load on the etching rate change was investigated. The extent of the etching rate change was found to be almost constant irrespective of the amount of the applying load. Therefore, the height of the structure could be controlled simply by the etching depth as far as the densified portion remains beneath the glass surface. And some example micro-patterns were fabricated in this process. Various kinds of indentation methods were employed, including scanning a pointed tool under a load and wet abrasive blast. The patterns can be freely drawn by the use of numerical control (NC) machine. Mold pattern can be also applied, which enables drawing many lines simultaneously. In every method, the heights of the patterns were confirmed to be very uniform. This new type of the micro-fabrication method was referred to as “SMIL (Stress Masked Image Lithography)”.

Keywords: PACS; 68.35.bj; 82.40.−g; 81.65.CfGlass; Etching; Micro-fabrication; Patterning

Electron field emission from amorphous carbon with N-doped nanostructures pyrolyzed from polyaniline by Long Lin; Haijun Niu; Milin Zhang; Wei Song; Zhe Wang; Xuduo Bai (pp. 7250-7254).

Carbon-based materials have been of great interest due to their potential application in cold cathodes for field emission displays and other vacuum microelectronic devices. Pyrolyzed polyaniline (PPANI) with N-doped nanostructures was prepared by pyrolysis of polyaniline at high temperature of 900°C. The morphologies and microstructures were investigated by scanning electron microscopy, transmission electron microscopy, AFM, Raman spectroscopy, and X-ray photoelectron spectroscopy. It was found that there were sp²C–N and sp³C–N bonds between the nitrogen and the carbon atoms in the nanostructures of the PPANI obtained. The electron field emission investigations showed that the turn-on field and effective work function ϕ_e of PPANI were 1.7V/μm and 0.010eV which were lower than N-doped amorphous carbon films obtained by other methods.

Keywords: Nanomaterials; Polymers; Electronic materials

Preparation and characterization of slice-like Cu₂(OH)₃NO₃ superhydrophobic structure on copper foil by Linghao Kong; Xinhua Chen; Guangbin Yang; Laigui Yu; Pingyu Zhang (pp. 7255-7258).

Superhydrophobic structure was prepared on copper foil via a facile solution-immersion method. Thus slice-like Cu₂(OH)₃NO₃ crystal was prepared on the surface of the copper foil by sequential immersing in an aqueous solution of sodium hydroxide and cupric nitrate. And the superhydrophobic structure was obtained by modifying the slice-like Cu₂(OH)₃NO₃ crystal with 1 H,1 H,2 H,2 H-perfluorodecyltriethoxysilane (FAS-17). The morphologies, chemical compositions and states, and hydrophobicity of the surface-modifying films on the copper foil substrates were analyzed by means of scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and water contact angle measurement. Moreover, the thermal stability of the slice-like structure was also evaluated using thermogravimetric analysis (TGA). It was found that roughening of the copper foil surface helped to increase the hydrophobicity to some extent, but no superhydrophobicity was obtained unless the slice-like Cu₂(OH)₃NO₃ crystal formed on the Cu substrate was modified with 1 H,1 H,2 H,2 H-perfluorodecyltriethoxysilane. Besides, the superhydrophobicity of the FAS-17-modified slice-like Cu₂(OH)₃NO₃ structure was closely related to the surface morphology. And this hydrophobic structure retained good superhydrophobic stability at elevated temperature and in long-term storage as well, which should be critical to the application of Cu-matrix materials in engineering.

Keywords: Copper foil; Trihydroxy cupric nitrate; Superhydrophobic surface; Contact angle

The effect of rf power on the growth of InN films by modified activated reactive evaporation by Kuyyadi P. Biju; Mahaveer K. Jain (pp. 7259-7265).

We report the effect of rf power on the structural, optical and electrical properties of InN films grown by modified activated reactive evaporation. In this technique, the substrates were kept on the cathode instead of ground electrode. The films grown at higher rf power shows preferential c-axis orientations for both silicon and glass substrates. The films prepared at 100W show best structural, electrical and optical properties. The c-axis lattice constant was found to decrease with increase in rf power which can be attributed to reduction in excess nitrogen in the films. The band gap decreases with increase in rf power due to Moss–Burstein shift. The decrease in carrier concentration and optical band gap with increase in rf power can also be related to excess nitrogen in the film. The Raman spectra shows a red shift in the A₁(LO) and E₂ (high) mode from the reported value. The possible origin of the present large band gap is due to Moss–Burstein shift. The new film growth method opens opportunities for integrating novel substrate materials with group III nitride technologies.

Keywords: InN; Modified activated reactive evaporation

Enhanced optical and field emission properties of CTAB-assisted hydrothermal grown ZnO nanorods by U.N. Maiti; S. Nandy; S. Karan; B. Mallik; K.K. Chattopadhyay (pp. 7266-7271).

We have developed a simple N-cetyl- N, N, N-trimethyl ammonium bromide (CTAB)-assisted hydrothermal route for the production of ZnO one-dimensional (1D) nanostructures on zinc foil at reaction temperature of 160°C. With the increase of CTAB concentration, the one-dimensional structures change from microrod to a mixture of nano- and microrod and finally to nanorods. X-ray diffraction studies confirmed the proper phase formation of the grown nanostructures. The room temperature photoluminescence spectra showed that ZnO nanostructures prepared with increased CTAB concentration exhibited enhanced band edge UV emission and also blue shift of the emission peak. All the samples show no defect related green emission. Field emission property of the 1D structures has been investigated in detail. By tuning the CTAB concentration, the field emission property was optimized. The nanorods synthesized with high CTAB showed turn-on and threshold fields of 3.2 and 5V/μm, respectively, which are comparable to the values for vapour phase synthesized high field emitting ZnO nanostructures.

Keywords: PACS; 61.46.Hk; 81.20.Ka; 78.55.−m; 79.70.+qZnO nanorods; Chemical synthesis; Photoluminescence; Field emission

Influence of long-term aqueous exposure on surface properties of plasma sprayed oxides Al₂O₃, TiO₂ and their mixture Al₂O₃–13TiO₂ by Mika Harju; Mikael Järn; Per Dahlsten; Jarl B. Rosenholm; Tapio Mäntylä (pp. 7272-7279).

The surface properties of plasma sprayed Al₂O₃- and TiO₂-based coating materials were characterized in order to investigate the influence of surface strain and phase inhomogenity. The materials were water exposed up to 8 months. The bulk crystallographic structure, dissolution behaviour, effective charge (zeta potential, isoelectric point), surface compositions and oxidation states were determined. In addition, the properties of the aging solutions, such as conductivity, supernatant pH (point of zero charge), and redox potential, were monitored during aging.It was shown that the materials were stable under aging conditions, but that considerable surface rearrangements, such as dissolution–reprecipitation and surface site redistributions may occur. However, overall only minor changes in surface properties results from this restructuring process.

Keywords: Plasma spraying; Alumina; Titania; Zeta potential; IEP; Dissolution; Surface state

X-ray photoelectron and X-ray Auger electron spectroscopy studies of heavy ion irradiated C₆₀ films by Amit Kumar; F. Singh; Govind; S.M. Shivaprasad; D.K. Avasthi; J.C. Pivin (pp. 7280-7284).

The influence of 200MeV Au ion irradiation on the surface properties of polycrystalline fullerene films has been investigated. The X-ray photoelectron and X-ray Auger electron spectroscopies are employed to study the ion-induced modification of the fullerene, near the surface region. The shift of C 1s core level and decrease in intensity of shake-up satellite were used to investigate the structural changes (like sp² to sp³ conversion) and reduction of π electrons, respectively, under heavy ion irradiation. Further, X-ray Auger electron spectroscopy was employed to investigate hybridization conversion qualitatively as a function of ion fluence.

Keywords: Ion irradiation; Fullerene; X-ray photoelectron spectroscopy; X-ray-induced Auger electron spectroscopy

Structural, optical and magnetic properties of (ZnO)1−_x(MnO₂)_x thin films deposited at room temperature by S. Karamat; S. Mahmood; J.J. Lin; Z.Y. Pan; P. Lee; T.L. Tan; S.V. Springham; R.V. Ramanujan; R.S. Rawat (pp. 7285-7289).

The structural, magnetic and optical properties of (ZnO)1−_x(MnO₂)_x (with x=0.03 and 0.05) thin films deposited by pulsed laser deposition (PLD) were studied. The pellets used as target, sintered at different temperatures ranging from 500°C to 900°C, were prepared by conventional solid state method using ZnO and MnO₂ powders. The observation of non-monotonic shift in peak position of most preferred (101) ZnO diffraction plane in XRD spectra of pellets confirmed the substitution of Mn ions in ZnO lattice of the sintered targets. The as-deposited thin film samples are found to be polycrystalline with the preferred orientation mostly along (110) diffraction plane. The UV–vis spectroscopy of the thin films revealed that the energy band gap exhibit blue shift with increasing Mn content which could be attributed to Burstein–Moss shift caused by Mn doping of the ZnO. The deposited thin films exhibit room temperature ferromagnetism having effective magnetic moment per Mn atom in the range of 0.9–1.4 μ_B for both compositions.

Keywords: Diluted magnetic semiconductor; Thin films; Pulsed laser deposition

Evaluation of nanoscale roughness measurements on a plasma treated SU-8 polymer surface by atomic force microscopy by Ferdinand Walther; Wolfgang M. Heckl; Robert W. Stark (pp. 7290-7295).

A comparison between roughness data obtained with an atomic force microscope (AFM) on different surfaces requires reliable roughness parameters. In order to specify the appropriate parameters for nanoscale roughness measurements, we compared the root mean square (rms) roughness and the relative surface area (sdr) as function of varying scan size, speed and pixel size. By using oxygen plasma (24kJ) treated SU-8 with an average rms roughness of 2.6±0.5nm as reference surface, the repeatability of the method was evaluated for dynamic (tapping) and contact mode. The evaluation of AFM images indicated a decrease of the effective tip radius after a few measurements. This degradation of the tip lowers the resolution of the image and can affect roughness measurements.

Keywords: PACS; 07.79.Lh; 73.61.Ph; 46.55._dAFM; Tip degradation; SU-8; Plasma treatment; Photoresist; Hydrophilisation; Polymer; Intermittent contact

Lanthanide-doped titanium dioxide layers as photocatalysts by M. Uzunova-Bujnova; R. Todorovska; D. Dimitrov; D. Todorovsky (pp. 7296-7302).

Films (∼0.5mg/cm²) from TiO₂ doped with 1–10mol% Ln³⁺ (Ln=La or Gd) are deposited on different types of substrates by spray-pyrolysis using ethylene glycol solutions of Ti⁴⁺–Ln³⁺ citric complexes as starting material and O₂ as a carrier gas. The films are post-deposition heated at 500°C. Their phase composition, crystal structure, morphology, sorption ability and photocatalytic activity are studied. Aqueous solution of methylene blue is applied as a model pollutant. A film with 5mol% La on Ti-coated stainless steel substrate shows significantly higher photocatalytic activity than the best performing samples produced from commercially available titania.

Keywords: PACS; 68.43.−h; 77.84.Dy; 81.15.−z; 82.50.−mTiO; ₂; Photocatalysis; Rare earths; Sorption; Thin films

The optical properties of ZnO/ZnMgO single quantum well grown by P-MBE by S.C. Su; Y.M. Lu; Z.Z. Zhang; C.X. Shan; B. Yao; B.H. Li; D.Z. Shen; J.Y. Zhang; D.X. Zhao; X.W. Fan (pp. 7303-7305).

In this paper, ZnO/Zn_0.9Mg_0.1O single quantum well (SQW) structures were fabricated on c-plane sapphire (Al₂O₃) substrate by plasma-assisted molecular beam epitaxy (P-MBE). The photoluminescence (PL) peak of the SQW shifted from 3.31 to 3.37eV as the well layer thickness was decreased from 6 to 2nm. The spectral linewidth increases with temperature due to the scattering of excitons with acoustic and optical phonons. The transition energy of the localized exciton in the ZnO/Mg_0.1Zn_0.9O SQW with well width of 3nm was found to be about 3.407eV at 80K, consistent with theoretical calculation. The first subband energies in the conduction and valence band were calculated to be 49 and 11meV, respectively.

Keywords: ZnMgO; SQWs; P-MBE; ZnO

A displacement sensing nanoindentation study of tribo-mechanical properties of the Ni–Co system by S. Graça; R. Colaço; A.J. Kulik; R. Vilar (pp. 7306-7313).

An analysis of the tribo-mechanical properties of the Ni–Co system, at the submicrometric contact scale, is conducted using displacement sensing nanoindentation. In particular, the influence of contact depth and surface finishing methods on the hardness, H, and Young's modulus, E, of the materials is analysed. Mechanically and electrolitically polished samples were tested with a conospherical indenter using a range of loads between 0.05 and 10mN. It is shown that the hardness of these materials depends on the surface finishing method and increases with decreasing contact depth, while the Young's modulus is relatively insensitive to contact depth. Furthermore, sample polycrystallinity leads to a large scattering of hardness values in Co-rich samples and of Young's modulus values in Ni-rich ones. The combined parametric ratio H/E, which can be related to the tribological behaviour of the material, was found to be higher in samples with Co content larger than 80wt.%.

Keywords: Hardness; Young's modulus; Displacement sensing nanoindentation; Ni–Co system

Evolution of TiO₂ coating layers on lamellar sericite in the presence of La³⁺ and the pigmentary properties by Min Ren; Hengbo Yin; Aili Wang; Chen Ge; Chunyan Liu; Longbao Yu; Tingshun Jiang; Yumin Liu; Ying Hang (pp. 7314-7320).

TiO₂-coated sericite powders were prepared by the chemical deposition method starting from lamellar sericite and TiCl₄ in the presence or absence of La³⁺ cations. After calcination at 900°C for 1h, the resultant TiO₂ nanoparticles on the sericite surfaces existed in anatase phase. The light scattering indexes of the TiO₂-coated lamellar sericite powders were dozens of times higher than that of the naked lamellar sericite powders. The presence of La³⁺ in the deposition solution was beneficial to the formation of the small-sized anatase TiO₂ nanoparticles, resulting in the formation of the dense and uniform island-like TiO₂ coating layers in a large range of the weight ratios of TiO₂ to sericite from 5% to 20%. The TiO₂-coated lamellar sericite powders prepared in the presence of La³⁺ had higher light scattering index than that prepared in the absence of La³⁺. XPS analysis shows that when La³⁺ cations were absent in the reaction solution, TiO₂ coating layers anchored at the sericite surface via the Ti–O–Si and Ti–O–Al bonds. The presence of La³⁺ cations caused the formation of Si–O–La and Al–O–La bonds at the sericite surface and Ti–O–La bond at the surface of TiO₂ coating layers. After coating TiO₂ on the sericite surface, the yellowness of the TiO₂-coated sericite powders obviously increased and the brightness slightly decreased.

Keywords: Lamellar sericite; TiO; ₂; coating; Lanthanum; Pigmentary property

Crystalline morphologies of P(VDF-TrFE) (70/30) copolymer films above melting point by Weiping Li; Yuejin Zhu; Dayin Hua; Peiqing Wang; Xiaorong Chen; Jie Shen (pp. 7321-7325).

To further understand the crystallization behavior from melts of P(VDF-TrFE) (70/30) copolymer, the morphologies of P(VDF-TrFE) copolymer thin and ultra-thin films are studied by AFM. It is found that P(VDF-TrFE) (70/30) copolymer films exhibit morphologic transition from big grains to fiber-like rods above melting point. And this may be on account of the molecule chains plastic flow and self-organization, corresponding to polymer homoepitaxy.

Keywords: Crystallization; Melting point; AFM

Effect of heat treatment on the structure of incorporated oxalate species and photoluminescent properties of porous alumina films formed in oxalic acid by I. Vrublevsky; A. Jagminas; S. Hemeltjen; W.A. Goedel (pp. 7326-7330).

The present work focuses on the use of IR spectroscopy and photoluminescence spectral measurements for studying the treatment temperature effect on the compositional and luminescent properties of oxalic acid alumina films. In line with the recent researches we have also found that heat treatment of porous alumina films formed in oxalic acid leads to considerable changes in their photoluminescence properties: upon annealing the intensity of photoluminescence (PL) increases reaching a maximum at the temperature of around 500°C and then decreases. IR spectra of as-grown and heat-treated films have proved that PL emission in the anodic alumina films is related with the state of ‘structural’ oxalate species incorporated in the oxide lattice. These results allowed us to conclude that PL behavior of oxalic acid alumina films can be explained through the concept of variations in the bonding molecular orbitals of incorporated oxalate species including σ- and π-bonds.

Keywords: Photoluminescence; Anodic alumina; π-Bonds; Delocalized electrons; Oxalic acid

Electroless plating of copper on polyimide films modified by surface-initiated atom-transfer radical polymerization of 4-vinylpyridine by Liang Li; Guoping Yan; Jiangyu Wu; Xianghua Yu; Qingzhong Guo; Entang Kang (pp. 7331-7335).

Surface modification of polyimide (PI) films were first carried out by chloromethylation under mild conditions, followed by surface-initiated atom-transfer radical polymerization (ATRP) of 4-vinylpyridine (4VP) from the chloromethylated PI surfaces. The composition and topography of the PI surfaces modified by poly(4-vinylpyridine) (P4VP) were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The P4VP brushes with well-preserved pyridine groups on the PI surface was used not only as the chemisorption sites for the palladium complexes without prior sensitization by SnCl₂ solution during the electroless plating of copper, but also as an adhesion promotion layer to enhance the adhesion of the electrolessly deposited copper to the PI surfaces. The T-peel adhesion strength of the electrolessly deposited copper on the modified PI surface could reach about 6.6N/cm. Effects of the polymerization time and the activation time in the PdCl₂ solution on the T-peel adhesion strength of the electrolessly deposited copper in the Sn-free process to the modified PI surface were also studied.

Keywords: PACS; 82.40.−g; 82.65.+rElectroless plating; Copper; Polyimide; Surface-initiated ATRP; 4-Vinylpyridine

Direct observation of slow morphological transformations and wetting behavior of pulsed laser deposited sub-monolayer gold on (0001) sapphire in atmosphere by L.M. Kukreja; B. Koslowski; R. Steiner; A. Plettl; P. Ziemann (pp. 7336-7341).

Using high-resolution atomic force microscope we observed in ambient atmosphere the slow morphological transitions of the incipient adlayer of gold grown on (0001) sapphire substrate by pulsed laser deposition. The equivalent average uniform thickness of the gold deposition was about 0.55Å, which is about one-fourth of its monolayer. A dynamic simulation revealed that about 10% of the gold was implanted into the substrate up to the depth of about 3.3nm and the top monolayer of the sapphire surface was almost completely depleted of oxygen atoms due to the preferential sputtering by the plume particles. The gold adlayer transformed into a labile phase which enhanced the surface roughness and had a preferred orientation of a wavy structure during 24h of the deposition. The auto-correlation function of this wavy structure in labile metastable phase revealed two-fold symmetry and provided a preferential size of about 4nm (peak to peak) with a mean separation of 8nm. At the end of about 6 days this phase was found to completely transform into an apparently de-wetted phase of beads with average in-plane diameter of ∼20nm and height of ∼7nm having large size distribution. Each bead was seen to have coating of a concentric corona layer, which might be that of the condensed moisture or other gaseous species from atmosphere because subjecting these samples to vacuum removed this layer. These observations shed light on the dynamics of the pulsed laser deposited metastable gold adlayer in the incipient stage of its growth on sapphire and their wetting or de-wetting mechanisms in ambient atmosphere.

Keywords: Morphological transformations; Wetting properties; Incipient adlayer; Gold on sapphire; Pulsed laser deposition; Atomic force microscopy

Structural and tribological properties of CrTiAlN coatings on Mg alloy by closed-field unbalanced magnetron sputtering ion plating by Yongjing Shi; Siyuan Long; Shicai Yang; Fusheng Pan (pp. 7342-7350).

In this paper, a series of multi-layer hard coating system of CrTiAlN has been prepared by closed-field unbalanced magnetron sputtering ion plating (CFUBMSIP) technique in a gas mixture of Ar+N₂. The coatings were deposited onto AZ31 Mg alloy substrates. During deposition step, technological temperature and metallic atom concentration of coatings were controlled by adjusting the currents of different metal magnetron targets. The nitrogen level was varied by using the feedback control of plasma optical emission monitor (OEM). The structural, mechanical and tribological properties of coatings were characterized by means of X-ray photoelectron spectrometry, high-resolution transmission electron microscope, field emission scanning electron microscope (FESEM), micro-hardness tester, and scratch and ball-on-disc tester. The experimental results show that the N atomic concentration increases and the oxide on the top of coatings decreases; furthermore the modulation period and the friction coefficient decrease with the N₂ level increasing. The outstanding mechanical property can be acquired at medium N₂ level, and the CrTiAlN coatings on AZ31 Mg alloy substrates outperform the uncoated M42 high speed steel (HSS) and the uncoated 316 stainless steel (SS).

Keywords: CrTiAlN coating; Closed-field unbalanced magnetron sputtering ion plating; Chemical state; Morphology; Microindentation; Tribological property

Growth and real time corrosion resistance monitoring of lead decanoate coatings by Annemie Adriaens; Frank De Bisschop; Mark Dowsett; Bart Schotte (pp. 7351-7355).

Lead is very susceptible to corrosion in the presence of organic acids and humidity. A potential countermeasure is to apply a lead carboxylate coating by immersing the metal in a sodium carboxylate solution/suspension. In this work we report on the degree of surface coverage and the corrosion resistance of a lead decanoate Pb(C₁₀)₂ coating as a function of treatment time. Results show that the surface coverage reaches 91% after 15min and about 100% after 1h in a 0.05M sodium decanoate solution. The corrosion resistance, as indicated by electrochemical impedance spectroscopy, continues to increase even after 6h of immersion. In addition, we show that in the case of planar transport, a diffusion layer of 17mm thickness exists, wherein the sodium decanoate concentration drops linearly from its bulk value to almost zero at the solid/surface interface.

Keywords: PACS; 81.65.Kn; 68.47.DeLead; Corrosion; Coatings; Growth mechanism

Growth, coalescence, and electrical resistivity of thin Pt films grown by dc magnetron sputtering on SiO₂ by J.S. Agustsson; U.B. Arnalds; A.S. Ingason; K.B. Gylfason; K. Johnsen; S. Olafsson; J.T. Gudmundsson (pp. 7356-7360).

Ultra thin platinum films were grown by dc magnetron sputtering on thermally oxidized Si (100) substrates. The electrical resistance of the films was monitored in situ during growth. The coalescence thickness was determined for various growth temperatures and found to increase from 1.1nm for films grown at room temperature to 3.3nm for films grown at 400°C. A continuous film was formed at a thickness of 2.9nm at room temperature and 7.5nm at 400°C. The room temperature electrical resistivity decreases with increased growth temperature, while the in-plain grain size and the surface roughness, measured with a scanning tunneling microscope (STM), increase. Furthermore, the temperature dependence of the film electrical resistance was explored at various stages during growth.

Keywords: PACS; 68.37.Ef; 73.61.; −; r; 73.61.At; 81.05.Bx; 81.15.Cd In situ; resistivity; Coalescence; Thin film; Magnetron sputtering; STM

Isothermal decomposition behavior of the high nitrogen concentration γ-Fe[N] prepared from pure iron by Zhijun Jiang; Xiaoling Li; Jianfeng Gu; Mingjuan Hu; Zuchang Zhu (pp. 7361-7364).

The isothermal decomposition characteristic of the homogeneous high nitrogen austenitic samples prepared by a new multi-stage nitriding process was investigated by SEM and TEM in this paper. Lamellar-structure precipitations arranged on the decomposed austenite grain boundaries (GBs) and the flaky γ′ particles and network-structure precipitations appeared inside of the γ matrix. The extra high Vickers hardness more than 800HV was found in the 5-h aged samples, which was different from those of the bainitic/martensitic structures in Fe–C alloys. The SAED analysis indicates the γ′ has the coherent relation with the parent γ-Fe[N] phase and the interstitial nitrogen atoms are inclined to aggregate on {110}γ′/γ planes, which also contributes to the hardness of the matrix.

Keywords: PACS; 61.10.Nz; 82.30.Lp; 77.84.BwHeat treatment; Hardness; High nitrogen steels; Isothermal transformation; Precipitation

Synthesis and electronic behaviors of TiO₂/carbon clusters/Cr₂O₃ composite materials by H. Miyazaki; H. Matsui; T. Nagano; S. Karuppuchamy; S. Ito; M. Yoshihara (pp. 7365-7369).

Nano-structured TiO₂/carbon clusters/Cr₂O₃ composite material has been successfully obtained by the microwave treatment of a TiO(acac)/Cr(acac)₃/epoxy resin complex. The compositions of the composite materials were determined using ICP, elemental analysis and surface characterization by SEM–EDX, TEM and XRD. ESR spectral examinations suggest the possibility of an electron transfer in the process of TiO₂→carbon clusters→Cr₂O₃ with an oxidation site at TiO₂ particles and a reduction site at Cr₂O₃ particles. The preliminary experimental results show that the calcined materials could decompose methylene blue under visible-light irradiation.

Keywords: PACS; 71.20.Rv; 71.20.Nr; 72.80.Tm; 73.63.Bd; 74.25.JbNano-structures; Polymers; Carbon clusters; Titanium dioxide; Electron transfer

Wetting characteristics of ZnO smooth film and nanowire structure with and without OTS coating by Li-Yu Lin; Hyun-Joon Kim; Dae-Eun Kim (pp. 7370-7376).

ZnO is an important material that is used in a variety of technologies including optical devices, sensors, and other microsystems. In many of these technologies, wettability is of great concern because of its implications in numerous surface related interactions. In this work, the effects of surface morphology and surface energy on the wetting characteristics of ZnO were investigated. ZnO specimens were prepared in both smooth film and nanowire structure in order to investigate the effects of surface morphology. Also, a hydrophobic octadecyltrichlorosilane (OTS) coating was used to chemically modify the surface energy of the ZnO surface. Wettability of the surfaces was assessed by measuring the water contact angle. The results showed that the water contact angle varied significantly with surface morphology as well as surface energy. OTS coated ZnO nanowire specimen had the highest contact angle of 150°, which corresponded to a superhydrophobic surface. This was a drastic difference from the contact angle of 87° obtained for the smooth ZnO film specimen. In addition to the initial contact angle, the evolution of the water droplet with respect to time was investigated. The wetting state of water droplet was analyzed with both Wenzel and Cassie-Baxter models. Spontaneous and gradual spreading, together with evaporation phenomenon contributed to the changing shape, and hence the varying contact angle, of the water droplet over time.

Keywords: Contact angle; Nanowire; Superhydrophobic; Wetting; ZnO

Laser-assisted decontamination—A wavelength dependent study by J. Padma Nilaya; Pallavi Raote; Aniruddha Kumar; Dhruba J. Biswas (pp. 7377-7380).

We present here the experimental results on cleaning of radioactive dielectric particulates, loosely deposited on stainless steel, by coherent light of 1064nm wavelength and its three harmonics occurring at 532nm, 355nm and 266nm, derived from an Nd-YAG laser. For the initial few exposures, the decontamination factor has been found to be highest when exposed to 1064nm radiation. With increasing number of exposures, however, the radiation with reducing wavelength assumes a more important role as a cleaning agent. The observation of almost no cleaning with 1064nm and much reduced cleaning with its harmonics when the contamination is deposited on a transparent substrate confirms the dominant role played by metal substrate towards expelling the loose particulates from its surface.

Keywords: PACS; 42.55.−f; 42.62.−bLaser-assisted cleaning; Decontamination; Wavelength dependence

Energy distribution of plasma-assisted electron and ion emission from TGS single crystals by B. Konieczna; M. Wachowiak-Cicha; K. Biedrzycki (pp. 7381-7385).

Electron and ion emission accompanying non-thermal plasma processes, produced at the surface of TGS single crystals under driving ac electric field exceeding 10³V/cm, have been carried out. These plasma-assisted emission of electrons and ions were examined by means of time and energy distribution measurements. The intensity of registered charges (electrons and ions) displayed on the 2ms time scale are represented by two distinct peaks. Time dependent energy spectrum of charges, detected under our experimental conditions, involves electrons and ions with maximum energy up to 30–40eV for first peaks and up to 70–80eV for second one. Additionally, the energy of electrons is focused at about 10–15eV for first and second peaks and about 60–70eV for second ones; the ion energy spectrum for both peaks exhibits only distinct low energy maximum focused at about 5–15eV.

Keywords: PACS; 77.84.Fa; 77.80.Fm; 79.90.+bFerroelectrics; TGS; Electron and ion emission; Energy distribution

Investigation of the surface reactivity of a sol–gel derived glass in the ternary system SiO₂–CaO–P₂O₅ by Mohamed Mami; Anita Lucas-Girot; Hassane Oudadesse; Rachida Dorbez-Sridi; Fatima Mezahi; Elodie Dietrich (pp. 7386-7393).

A new glass formulation, with the molar composition 60% SiO₂–35% CaO–5% P₂O₅, was synthesized using the sol–gel process, for applications as biomaterial in orthopaedic or maxillo facial surgery. Pellets, made of glass powder, were uniaxially compacted and soaked in simulated body fluid (SBF) for up to 7 days at 37°C to evaluate glass bioactivity. Ionic exchanges at the interface glass-SBF were evaluated by studying evolutions of calcium, phosphorus and silicon concentrations in SBF using ICP-OES. Changes in glass surface, and the formation of crystalline phases were analyzed using XRD, SEM, EDS and FTIR methods.Results form ICP-OES showed a high reactivity of the glass surface with a very high and continuous release of calcium, a limited glass dissolution and an uptake of phosphorous from SBF. Results from both FTIR and XRD analysis indicated that the glass surface was progressively covered by two different phases: CaCO₃ as calcite and a carbonated apatite layer. The formation of these phases, following two different schemas, was observed after 2h of immersion and confirmed after 7 days. SEM micrographs and EDS analysis demonstrated that the main phase, a carbonated apatite, was present as micro-spheroids and the secondary phase, calcite, was materialized by agglomerates which have diameters up to 10–15μm. These results are in accordance with a bioactive feature of the glass studied.

Keywords: Sol–gel processing; Exchange; Surface; Body fluid

Study by EELS and EPES of the stability of InPO₄/InP system by A. Ouerdane; M. Bouslama; M. Ghaffour; A. Abdellaoui; K. Hamaida; Z. Lounis; Y. Monteil; N. Berrouachedi; A. Ouhaibi (pp. 7394-7400).

The goal of this research is to highlight the effectiveness of associating the spectroscopic methods EELS and EPES in the study of thin film grown on substrates. We use the great sensitivity of the Electron Energy Loss Spectroscopy (EELS) and the Elastic Peak Electron Spectroscopy (EPES) to study native InPO₄ oxide of thin thickness (10Å) grown on InP by UV/ozone oxidation. By varying the primary energy of the electron beam and the incidence angle, we give interesting results related to the chemical and the physical analyses of InPO₄/InP system. These spectroscopic methods reveal the homogeneity of the chemical composition of InPO₄ on the surface. Furthermore, the electron irradiation of InPO₄/InP leads to the breaking of chemical bonds between the species of InPO₄ and InP to form a new oxide In₂O₃ on the surface. We show that the heating of InPO₄/InP at 450°C in UHV allows a good reconstruction of the surface with elimination of defects on the surface and at the interface. Thus, the surface becomes more stable to impede all oxidation processes due to the electron beam irradiation even for a time as long as 30min.

Keywords: EELS; EPES; Surface; Defects; Structure; Heating; Electron beam irradiation

Long-life bismuth liquid metal ion source for focussed ion beam micromachining application by P. Mazarov; A. Melnikov; R. Wernhardt; A.D. Wieck (pp. 7401-7404).

Liquid metal ion sources (LMISs) with Ga as ion species are widely used in focused ion beam (FIB) technology for micromachining and surface treatment on the sub-micron and nano-scale. Key features of a LMIS for investigating mechanical properties and 3D-microfabrication of materials are long life-time, high brightness, stable ion current and a highly effective milling ability for the material to be modified. In order to increase the material removal rate, heavier ions than Ga and their clusters should be applied. Bismuth (Bi) is the heaviest, non-radio-active element in the periodic table, is non-toxic and exhibits a low melting point. We have thus produced a long-life (about 1000h) Bi LMIS with a good beam performance, applicable in any FIB system. Since Bi is the only element in this source, it is not necessary to separate it from other ions by a mass filter. Investigation of the sputtering rate of NiTi shape memory alloys using Ga and Bi LMIS showed that, for the same experimental conditions, the material removal rate with using of Bi_n^k+ ions in a standard FIB machine without a mass separator is about five times larger compared to Ga⁺ ions. This use of Bi as LMIS-species is the ultimate breakthrough in sputtering applications.

Keywords: FIB; Bismuth LMIS; Sputter enhancement

Characterization and optical properties of nano-ceria synthesized by surfactant-mediated precipitation technique in mixed solvent system by M.G. Sujana; K.K. Chattopadyay; S. Anand (pp. 7405-7409).

Crystalline cerium oxide nanoparticles have been synthesized by surfactant-mediated precipitation technique in acetone/water mixed solvent system. The cerium nitrate hexahydrate as precursor and non-ionic surfactant Tween 80 were taken in acetone/water system and precipitated with ammonia at pH 10. The sample was then calcined for 2h in the temperature range of 200–800°C and characterized by X-ray diffraction (XRD), FTIR, BET surface area and TEM. It was found from XRD studies that the crystallite size increased with calcination temperature from 3nm to 13nm and the surface area was found to be 133m²/g for 400°C calcined sample. The particle size obtained from high-resolution transmission electron microscope (HRTEM) was in the range of 4.5nm with uniform shape and narrow particle size distribution. The diffraction pattern completely indexed with the cubic fluorite structure of CeO₂. The calcined cerium oxide nanoparticles showed strong UV absorption and room temperature photoluminescence (PL).

Keywords: Nano-crystalline; Cerium oxide; Surfactant; Calcination; Mixed solvent

The effect of suspension bath composition on the composition, topography and structure of electrolessly deposited composite four-component Ni–W–P–ZrO₂ coatings by B. Szczygieł; A. Turkiewicz (pp. 7410-7416).

Composite four-component Ni–W–P–ZrO₂ coatings were electrolessly deposited from a bath with different concentrations of aminoacetic acid (glycine—the complexing agent), sodium tungstate(VI) and zirconium(IV) oxide at different pH values. Concentration distribution curves were determined for nickel–aminoacetic acid complexes as a function of the bath pH at different metal ion/complexing agent concentration ratios. It has been shown that the bath pH and the complexing agent concentration have the strongest effect on the composition and structure of the coatings. As the bath pH is lowered and the aminoacetic acid concentration is increased, the phosphorous content in the coating increases. In composite four-component Ni–W–P–ZrO₂ coatings (similarly as in electroless two- and three-component nickel coatings), as the phosphorous content in the coating increases, the crystallinity of the coating decreases. Diffraction patterns deposited at pH 5 have only one peak corresponding to nickel: Ni(111) at 2 Θ=44°. In the diffraction patterns at pH 8 one can observe sharp peaks for 5 crystalline planes: (200), (220), (311), (222) and dominant (111). After heat treatment at 400°C for 1h a nickel phosphide (Ni₃P) phase appears (besides the crystalline nickel phase) in the coatings. Heat treatment also results in an increase in crystallite size from 1.5 to 2.0 to about 3.0nm.

Keywords: Electroless nickel; Alloy coating; Composite coating; Crystalline structure; Zirconium dioxide; Glycine

Development and optimisation of FeCoHfN soft magnetic thin films with high-frequency characteristics by Cheng-Lun Kuo; Shandong Li; Jenq-Gong Duh (pp. 7417-7420).

Ferromagnetic amorphous Fe–Co–Hf–N thin films with a gradient concentration of Hf doping were fabricated by rf reactive magnetron sputtering. The evaluated magnetic properties and high-frequency characteristics were sensitive to the doping contents. In this study, a new technology was used to deposit a series of Fe–Co–Hf–N thin films on which gradient concentration of Hf was present. By this new deposited technology, the films existed residual stress, and thus the stress-induced anisotropy field was enhanced. Therefore, the as-deposited films without postannealing exhibited larger anisotropy field ( H_k) of 150Oe. In addition, coercivity ( H_C) of less than 5Oe in both easy and hard axes, and electrical resistivity ( ρ) of 500μΩcm were obtained. The permeability measurement showed a permeability of around 100 at 3GHz and a ferromagnetic resonance frequency ( f_FMR) in excess of 3GHz. It is expected that this film should be promising for practical applications as a high-frequency ferromagnetic material.

Keywords: Ferromagnetic; Thin films; FeCo; High frequency; Anisotropy

Numerical investigation on laser-produced microstructure of metal under non-melting condition by Yongjun Shi; Zhenqiang Yao; Feng Liu; Yaoguang Qi (pp. 7421-7426).

Surface topography plays an important role on the improvement of tribological properties under hydrodynamic or elasto-hydrodynamic lubrication conditions. Laser texturing processes that give a regular surface topography have been extensively analyzed, however, the micro-convex features produced have a regular volcano profile which is not in favor of dynamic pressure lubrication and enhancing the wear-resistant ability. To obtain a functional surface topography, a new process method by laser non-melting is proposed. The forming mechanism of the micro-convex features produced has been analyzed. The main reason for the formation was found to be due to the free expansion of the heating area being restricted by the surrounding cool material. The effect of different process parameters on the height and width of the micro-convex features is investigated. Finally, a scanning strategy to control the surface micro-convex feature length is presented. The numerical results show that smooth micro-convex features can be achieved by selecting the correct heating paths and process parameters.

Keywords: Laser heat process; Microstructuring; Tribology; Metal

Electroless preparation and characterization of magnetic Ni–P plating on polyurethane foam by Wenbin Yang; Shikai Luo; Bingjie Zhang; Zhong Huang; Xiaohong Tang (pp. 7427-7430).

Magnetic Ni–P plating was coated on surface of polyurethane (PU) foam by electroless plating technique. Morphology, composition, structure, thermal decomposing behavior and magnetic property of PU foam before and after plating were characterized by scanning electron microscopy (SEM), energy diffraction spectrum (EDS), X-ray photoelectron spectroscopy (XPS), infrared spectrometer (IR), X-ray diffraction (XRD), thermogrametric analysis (TG) and vibrating sample magnetometer (VSM), respectively. The results showed that the Ni–P plating was composed by particles whose diameters were in the range of 1–2μm. Because of the Ni–P plating coated on surface of PU foam, peak intensity of the plated PU foam in IR and XRD were lower than those before plating. TG curves of PU foam before and after plating were composed of two decomposing stages. Because part of Ni in Ni–P plating was oxidized, TG curve of the plated PU foam was uptilt during 650–1000°C. The plated PU foams are magnetic and can be used in some special application.

Keywords: Polyurethane foam; Electroless plating; Magnetic; Preparation; Characterization

Statistical analysis of paper surface microstructure: A multi-scale approach by Pierre Vernhes; Jean-Francis Bloch; Christophe Mercier; Anne Blayo; Bernard Pineaux (pp. 7431-7437).

Paper properties such as gloss, friction or printability strongly depend on the surface roughness. However, this dependence on the roughness in relation to the measurement scale is not systematically taken into account. Paper surface topography is here studied in a multi-scale approach with the help of a focus variation device. For each measurement scale, statistical parameters were calculated to describe the surface. We isolated among the long list of parameters calculated those that were relevant for paper surface topography analysis. A new method of characterization of paper surface roughness is proposed based on a scaling analysis taken from either profile or surface data. Depending on the scale of analysis different fractal stages were exhibited. The influence of the step of discretization on the roughness parameters was also investigated.

Keywords: Surface topography; Multi-scale analysis; Fractal analysis; Focus variation technique

Hydrophobicity-induced selective covering of carbon nanotubes with sol–gel sheaths achieved by ultrasound assistance by Ki Chul Park; Tomoaki Mahiko; Shingo Morimoto; Kenji Takeuchi; Morinobu Endo (pp. 7438-7445).

A simple construction of sol–gel sheaths onto the surface of multi-walled carbon nanotubes (MWCNTs) has been carried out in water by a hydrophobicity-induced covering with the assistance of ultrasound. The ultrasound assistance prevents in water an unregulated agglomeration induced by the hydrophobicity of MWCNTs and phenyl-containing sols, leading to a selective construction of sol–gel sheaths on the nanotube surface. The phenyl groups of the resulting sol–gel sheaths were successfully removed by air-oxidation to provide the MWCNTs covered with amorphous SiO₂ sheaths. The effect of the SiO₂ sheaths on the electrical and thermal properties of the SiO₂-MWCNT nanocomposites was evaluated from the electrical resistivities of the nanocomposites with two different SiO₂ concentrations and the thermal conductivities of their phenol-resin composites. The results indicate that the small increase of the SiO₂ concentration remarkably increases the electrical resistivity of the SiO₂-MWCNT nanocomposites. Furthermore, the SiO₂ sheaths have more directly influenced the thermal property of the polymer composites than the inside nanotubes.

Keywords: Multi-walled carbon nanotubes (MWCNTs); Sol–gel process; Amorphous silica (SiO; ₂; ); Nanocomposites; Thermal conductivity; Electrical resistivity

The comparative study on microstructure and properties of nano-CeO₂ and Sm₂O₃ particulate reinforced nickel-based composites by laser deposition by Shihong Zhang; Mingxi Li; Jae Hong Yoon; Tong Yul Cho; Chan Gyu Lee; Yizhu He (pp. 7446-7452).

Micron size Ni-based alloy (NBA) powders are mixed with both 1.5wt% nano-CeO₂ (n-CeO₂) and nano-Sm₂O₃ (n-Sm₂O₃) powders. These mixtures are coated on low carbon steel by laser deposition. Based on the thermodynamic characteristic of rare earth oxides, evolution of microstructure and variety of phase and properties of the coatings by the addition of n-CeO₂ and Sm₂O₃ powders to NBA have been investigated comparatively. The morphology of dendrite is transformed from bulky without n-CeO₂ and Sm₂O₃ into fine and compact with the addition of 1.5% n-CeO₂ and Sm₂O₃. And lamellar spacing of the eutectic of n-CeO₂/NBA is smaller than that of n-Sm₂O₃/NBA. The microhardness, wear resistance and corrosion resistance of the coatings are greatly improved by n-CeO₂ and Sm₂O₃ powder addition.

Keywords: Laser deposition; Rapid solidification; Rare earth; Particulate reinforced composites; Thermodynamics

Surface characterization on binary nano/micro-domain composed of alkyl- and amino-terminated self-assembled monolayer by S.H. Lee; T. Ishizaki; N. Saito; O. Takai (pp. 7453-7458).

The binary alkyl- and amino-terminated self-assembled monolayers (SAMs) composed of nano/micro-sized domains was prepared though a self-assembly technique. In addition, the wetting and electrostatic property of the binary SAMs was investigated by the analysis of the static and dynamic water contact angle and zeta-potentials measurement. The binary SAMs were also characterized by atomic force microscope (AFM), Kelvin probe force microscope (KPFM) and X-ray photoelectron spectroscopy (XPS). The domains on the binary SAMs were observed in topographic and surface potential images. The height of domain and the surface potential between octadecyltrichlorosilanes (OTS)-domain and n-(6-aminohexl)aminopropyl-trimethoxysilane (AHAPS)-SAM were about 1.1nm and −30mV. These differences of height and surface potential correspond to the ones between OTS and AHAPS. In XPS N 1s spectra, we confirmed the formation of binary SAMs by an amino peak observed at 399.15eV. The dynamic and the static water contact angles indicated that the wetting property of the binary SAMs was depended on the OTS domain size. In addition, static water contact angles were measured under the conditions of different pH water and zeta-potential also indicated that the electrostatic property of the binary SAMs depended on OTS domain size. Thus, these results showed that the wetting and electrostatic property on the binary SAMs could be regulated by controlling the domain size.

Keywords: Binary self-assembled monolayer; Wetting and electrostatic property; Zeta-potentials; Water contact angle

Room temperature ferromagnetism of Mn-doped SnO₂ thin films fabricated by sol–gel method by Yuhua Xiao; Shihui Ge; Li Xi; Yalu Zuo; Xueyun Zhou; Bangmin Zhang; Li Zhang; Chengxian Li; Xiufeng Han; Zhenchao Wen (pp. 7459-7463).

Sn1−_xMn_xO₂ ( x≤0.11) thin films spin-coated on Si (111) substrate were fabricated by sol–gel method. X-ray diffraction revealed that single-phase rutile polycrystalline structure was obtained for x up to about 0.078. Evolution of the lattice parameters and X-ray photoelectron spectroscopy studies confirmed the incorporation of Mn³⁺ cations into rutile SnO₂ lattice. Magnetic measurements revealed that all Sn1−_xMn_xO₂ thin films exhibit ferromagnetism at room temperature, which is identified as an intrinsic characteristic. Magnetization data showed that the average magnetic moment per Mn atom decreased and the coercivity increases with increasing Mn content. The origin of room temperature ferromagnetism can be understood in terms of the percolation of the bound magnetic polaron. Our experimental results prove that the sol–gel method is an effective method for fabrication of transition metal doped SnO₂ nanostructures with room temperature ferromagnetism by chemical synthesis.

Keywords: Room temperature ferromagnetic semiconductor; Sol–gel method; Mn-doped SnO; ₂; film; The percolation of bound magnetic polaron

Effect of carrier gas species and flow rates on the properties of ZnO thin films prepared by chemical vapor deposition using zinc acetate dihydrate by Liang-Chiun Chao; Meng-Yun Hsieh; Shih-Hsuan Yang (pp. 7464-7468).

ZnO thin films were prepared on (111) silicon substrates by sublimation of zinc acetate dihydrate utilizing argon and oxygen as the carrier gas. ZnO films prepared using oxygen as the carrier gas exhibit a week near-band-edge (NBE) emission and strong orange-red deep level emission, while ZnO films prepared using argon as the carrier gas shows a strong NBE emission and weak deep level green emission. The NBE emission energy position can be controlled to vary from 3.241 to 3.137eV utilizing a combination of argon and oxygen as the carrier gas. Secondary ion mass spectroscopy analysis indicates that the relative concentration of carbon to hydrogen in the ZnO film remains constant, suggesting the presence of hydrocarbons. The concentration of hydrocarbon can be reduced by using oxygen in the carrier gas.

Keywords: PACS; 81.05.Dz; 61.10.Nz; 61.14.QpZinc oxide; Hydrocarbon; Optical properties; SIMS

Studies on surface grafting of AAc/SSS binary monomers onto polytetrafluoroethylene by dielectric barrier discharge initiation by Zhen-Yu Xi; You-Yi Xu; Li-Ping Zhu; Fu Liu; Bao-Ku Zhu (pp. 7469-7476).

Polytetrafluoroethylene (PTFE) films were pre-treated by dielectric barrier discharge in atmospheric pressure with air as carrier gas. And then the hydrophilic sulfonate groups were introduced by the single step grafting method with binary monomer solution of acrylic acid (AAc) and sodium 4-styrenesulfonate (SSS). The effects of binary monomer ratio, reaction solution concentration and polymerization time on the degree of grafting were investigated. The surface chemical change was determined by Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). Morphological changes on the film surface were described using field emitting scanning electron microscopy (SEM) and atomic force microscopy (AFM). The surface hydrophilicity of the modified film was characterized through water contact angle measurement. It was found that the water contact angle of the film surface reduced significantly when compared with the original one, indicating the introduction of hydrophilic groups and improvement of the surface hydrophilicity.

Keywords: Polytetrafluoroethylene; Dielectric barrier discharge; Graft; Surface structure; Hydrophilicity; Sulfonate group

Structural and magnetic properties of CuO nanoneedles synthesized by hydrothermal method by M.A. Dar; Y.S. Kim; W.B. Kim; J.M. Sohn; H.S. Shin (pp. 7477-7481).

The copper oxide (CuO) nanoneedles were synthesized by a simple hydrothermal method. Field emission scanning electron microscopy revealed the formation of high-density CuO nanoneedles with ultrathin nanotip at low temperature. The X-ray diffraction (XRD) results showed that the CuO nanoneedles have monoclinic structure with single crystalline phase. High-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction results also assisted the products single crystalline nature. The magnetic properties of CuO nanoneedles were studied using a superconductor quantum interference device (SQUID) magnetometer, and revealing a ferromagnetic behavior of the CuO nanoneedles. The coercivity of CuO nanoneedles at 3K was estimated to be 42Oe. These CuO nanoneedles may be implicated to various applications such as drug delivery, magnetic resonance imaging and field emission devices.

Keywords: PACS; 87.64.Je; 79.60.Jv; 81.07.Bc; 87.64.BxCrystal growth; Nanomaterials; Copper oxide; Hydrothermal method; Field emission scanning electron microscopy

Annealing effects on electrical and optical properties of ZnO films deposited on GaAs by metal organic chemical vapor deposition by Jingchang Sun; Hongwei Liang; Jianze Zhao; Qiuju Feng; Jiming Bian; Ziwen Zhao; Heqiu Zhang; Yingmin Luo; Lizhong Hu; Guotong Du (pp. 7482-7485).

ZnO thin film was deposited on semi-insulating GaAs by metal organic chemical vapor deposition (MOCVD). In situ annealing treatments were carried out under different temperature. Hall and photoluminescence (PL) measurements showed that the electrical and optical properties of ZnO film were sensitively dependent on annealing temperature. The as-deposited ZnO film showed n-type conductivity and intense near band edge (NBE) emission combined with rather weak deep level (DL) emission. After annealing in the temperature of 520 and 560°C the films exhibit p-type conductivity, meanwhile secondary ion mass spectroscopy demonstrated arsenic ion was uniformly distributed in the ZnO films. Distinctly recombination of donor acceptor pair (DAP) was observed from the p-type ZnO film. The calculated arsenic related acceptor binding energy is nearly consistent with that of As_Zn–2V_Zn acceptor complex. When the annealing temperature up to 640°C, Ga ion began to diffuse into ZnO film and the film returned to n-type as well as donor related emission reappeared in the spectrum. The influence of GaAs substrate on the electrical properties of ZnO films was also discussed.

Keywords: PACS; 81.05.; 81.15.Gh; 85.40.Ry; 78.55.QrZnO/GaAs; Annealing; Electrical and optical properties

Oxidation of Ni(Pt)Si by molecular vs. atomic oxygen by Sudha Manandhar; Brian Copp; J.A. Kelber (pp. 7486-7493).

X-ray photoelectron spectroscopy (XPS) has been used to characterize the oxidation of a clean Ni(Pt)Si surface under two distinct conditions: exposure to a mixed flux of atomic and molecular oxygen (O+O₂;PO+O2=5×10⁻⁶Torr) and pure molecular oxygen (O₂;PO2=10⁻⁵Torr) at ambient temperatures. Formation of the clean, stoichiometric (nickel monosilicide) phase under vacuum conditions results in the formation of a surface layer enriched in PtSi. Oxidation of this surface in the presence of atomic oxygen initially results in formation of a silicon oxide overlayer. At higher exposures, kinetically limited oxidation of Pt results in Pt silicate formation. No passivation of oxygen uptake of the sample is observed for total O+O₂ exposure <8×10⁴L, at which point the average oxide/silicate overlayer thickness is 23 (3)Å (uncertainty in the last digit in parentheses). In contrast, exposure of the clean Ni(Pt)Si surface to molecular oxygen only (maximum exposure: 5×10⁵L) results in slow growth of a silicon oxide overlayer, without silicate formation, and eventual passivation at a total average oxide thickness of 8(1)Å, compared to a oxide average thickness of 17(2)Å (no silicate formation) for the as-received sample (i.e., exposed to ambient.) The aggressive silicon oxidation by atomic oxygen, results in Ni-rich silicide formation in the substrate and the kinetically limited oxidation of the Pt.

Keywords: XPS; Nickel silicide; Platinum; Oxidation; Atomic oxygen; Silicate

Porous silicon as efficient surface enhanced Raman scattering (SERS) substrate by F. Giorgis; E. Descrovi; A. Chiodoni; E. Froner; M. Scarpa; A. Venturello; F. Geobaldo (pp. 7494-7497).

Silver nanocrystallites are obtained through immersion of porous silicon samples in AgNO₃ solutions and a successive thermal annealing. The efficiency of nanostructures as surface enhanced Raman scattering (SERS) substrates is checked on cyanine-based dyes and horseradish peroxidase, evidencing detectable concentrations as low as 10⁻⁷ to 10⁻⁸M. The substrate efficiency is strictly related to the Ag particle morphology, which could yield to either local surface plasmons (LSP) coupled to individual particles or to inter-particle short-range interaction.

Keywords: PACS; 78.30.−j; 78.30.Jw; 87.64.kp; 73.20.Mf; 78.67.BfRaman spectroscopy; SERS; Porous silicon

Photooxidation of different organic dyes (RB, MO, TB, and BG) using Fe(III)-doped TiO₂ nanophotocatalyst prepared by novel chemical method by Tanmay K. Ghorai; Soumya K. Biswas; Panchanan Pramanik (pp. 7498-7504).

The nano-structured Fe(III)-doped TiO₂ photocatalysts with anatase phase have been developed for the oxidation of non-biodegradable different organic dyes like methyl orange (MO), rhodamine B (RB), thymol blue (TB) and bromocresol green (BG) using UV–Hg-lamp. The different compositions of Fe_xTi1−_xO₂ ( x=0.005, 0.01, 0.05, and 0.1) nanocatalysts synthesized by chemical method (CM), have been characterized by X-ray diffraction (XRD), UV–vis diffuse reflectance spectra, specific surface area (BET), transmission electronic microscopy (TEM) analysis, XPS, ESR and zeta potential. From XRD analysis, the results indicate that all the compositions of Fe(III) doped in TiO₂ catalysts gives only anatase phase not rutile phase. For complete degradation of all the solutions of the dyes (MO, RB, TB, and BG), the composition with x=0.005 is more photoactive compared all other compositions of Fe_xTi1−_xO₂, and degussa P25. The decolorization rate of different dyes decreases as Fe(III) concentration in TiO₂ increases. The energy band gap of Fe(III)-doped TiO₂ is found to be 2.38eV. The oxidation state of iron has been found to be 3+ from XPS and ESR show that Fe³⁺ is in low spin state.

Keywords: TiO; ₂; Fe(NO; ₃; ); ₃; ·9H; ₂; O; CM; Photochemical reaction

Impact of laser produced X-rays on the surface of gold by Hamid Latif; M. Shahid Rafique; M. Khaleeq-ur-Rahaman; R.S. Rawat; Abdul Sattar; Shahzad Naseem; P. Lee (pp. 7505-7511).

In the paper an attempt has been made to use the laser-induced plasma as an X-ray source for the growth of nanostructures on the surface of gold. For this purpose, an Nd:YAG laser operated at second harmonics ( λ=532nm, E=400mJ) is used to produce plasma from analytical grade 5N pure Al, Cu and W targets. An analytical grade (5N pure) gold substrate was irradiated by X-rays generated from Al, Cu and W plasma under the vacuum ∼10⁻⁴Torr. The surface was analyzed by two techniques, XRD and AFM. The aberrations in the XRD peaks show that there are significant structural changes in the exposed gold, in terms of decreased reflection intensities, increased dislocation line density, changes in the d-spacing and disturbance in the periodicity of the planes. AFM used to explore the topography of the irradiated gold reveals that regardless of the source, nm sized hillocks have been produced on the gold surface. The roughness of the surface has increased due to the growth of these hillocks.

Keywords: PACS; 52.50.Jm; 52.38.Mf; 52.38.Ph; 61.80.Cb; 61.72.LkLaser-induced plasma; X-rays; Surface modification; Hillocks formation

A study of interface characteristics in HfAlO/p-Si by deep level transient spectroscopy by Ning Zhan; Min Xu; David Wei Zhang; Fang Lu (pp. 7512-7515).

Deep level transient spectroscopy (DLTS) and high-frequency capacitance–voltage (HF-CV) measurement are used for the investigation of HfAlO/p-Si interface. The so-called “slow” interface states detected by HF-CV are obtained to be 2.68×10¹¹cm⁻². Combined conventional DLTS with insufficient-filling DLTS (IF-DLTS), the true energy level position of interfacial traps is found to be 0.33eV above the valance band maximum of silicon, and the density of such “fast” interfacial traps is 1.91×10¹²cm⁻²eV⁻¹. The variation of energy level position of such traps with different annealing temperatures indicates the origin of these traps may be the oxide-related traps very close to the HfAlO/Si interface. The interfacial traps’ passivation and depassivation effect of postannealing in forming gas are shown by comparing samples annealed at different temperatures.

Keywords: PACS; 73.20.At; 73.20.Hb; 73.40.Qv; 73.50.Gr; 81.65.RvSilicon; MOS capacitors; Deep level transient spectroscopy; Interface traps; Passivation; Annealing; Hafniun oxide; Aluminum

Co–B amorphous alloy nanochains with enhanced magnetization and electrochemical activity prepared in a biphasic system by Hui Li; Chengzuo Wang; Qingfei Zhao; Hexing Li (pp. 7516-7521).

Co–B amorphous alloy in the form of nanochains was prepared by chemical reduction of cobalt ions with borohydride in a dodecanethiol/water biphasic system. Such Co–B nanochains were comprised of uniform Co–B nanoparticles connected in one-dimension through electrostatic force between the induced dipoles. Dodecanethiol molecules played a key role in the formation of Co–B nanochains by covering Co–B nanoparticles via strong chemisorption bond which stabilized Co–B nanoparticles against gathering and also generated induced electric dipoles. The linear array of Co–B amorphous alloy nanoparticles resulted in the superposition of magnetic moments and also facilitated the electron transfer, leading to the enhanced magnetization and electrochemical activity.

Keywords: Co–B amorphous alloy; Nanochain; Uniform diameter; Biphasic system; Interface

Investigation of energy band gap and optical properties of cubic CdS epilayers by D.J. Kim; Y.-M. Yu; J.W. Lee; Y.D. Choi (pp. 7522-7526).

High quality cubic CdS epilayers were grown on GaAs (100) substrates by the hot-wall epitaxy method. The crystal structure of the grown epilayers was confirmed to be the cubic structure by X-ray diffraction patterns. The optical properties of the epilayers were investigated in a wide photon energy range between 2.0 and 8.5eV using spectroscopic ellipsometry (SE) and were studied in the transmittance spectra at a wavelength range of 400–700nm at room temperature. The data obtained by SE were analyzed to find the critical points of the pseudodielectric function spectra, 〈 ɛ( E)〉=〈 ɛ₁( E)〉+ i〈 ɛ₂( E)〉, such as E₀, E₁, E₂,E′0, andE′1 structures. In addition, the optical properties related to the pseudodielectric function of CdS, such as the absorption coefficient α( E), were investigated. All the critical point structures were observed, for the first time, at 300K by ellipsometric measurements for the cubic CdS epilayers. Also, the energy band gap was determined by the transmittance spectra of the free-standing film, and the results were compared with the E₀ structure obtained by SE measurement.

Keywords: PACS; 78.20.−e; 78.40.FyCubic CdS; Spectroscopic ellipsometry; Hot-wall epitaxy; Pseudodielectric function; Transmittance spectra

Fabrication of multilayered Ge nanocrystals embedded in SiO_xGeN_y films by Fei Gao; Martin A. Green; Gavin Conibeer; Eun-Chel Cho; Yidan Huang; Ivan Perez-Wurfl; Chris Flynn (pp. 7527-7530).

Multilayered Ge nanocrystals embedded in SiO_xGeN_y films have been fabricated on Si substrate by a (Ge+SiO₂)/SiO_xGeN_y superlattice approach, using a rf magnetron sputtering technique with a Ge+SiO₂ composite target and subsequent thermal annealing in N₂ ambient at 750°C for 30min. X-ray diffraction (XRD) measurement indicated the formation of Ge nanocrystals with an average size estimated to be 5.4nm. Raman scattering spectra showed a peak of the Ge–Ge vibrational mode downward shifted to 299.4cm⁻¹, which was caused by quantum confinement of phonons in the Ge nanocrystals. Transmission electron microscopy (TEM) revealed that Ge nanocrystals were confined in (Ge+SiO₂) layers. This superlattice approach significantly improved both the size uniformity of Ge nanocrystals and their uniformity of spacing on the ‘Z’ growth direction.

Keywords: PACS; 81.05.Cy; 81.07.Bc; 81.15.Cd; 81.40.Ef; 68.37.LpMultilayered Ge nanocrystals; Magnetron sputtering; Annealing; Superlattice approach; Uniformity

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Applied Surface Science (v.254, #22)

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Applied Surface Science (v.254, #22)