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Applied Surface Science (v.255, #23)

Superhydrophobic surface structures in thermoplastic polymers by interference lithography and thermal imprinting by Christian W.J. Berendsen; Marek Škereň; David Najdek; František Černý (pp. 9305-9310).

We present a method to produce superhydrophobic surfaces in thermoplastic polymer substrates. The method involves the creation of a nickel stamp using a customized laser interference lithography technique and electroplating processes. This stamp is used to emboss sub-micrometer periodic structures into the thermoplastic. The modified surface is coated with a hydrophobic plasma-polymerized hexafluoropropene layer. Surfaces with different periodicity and relief depth were created. On the surface with the highest aspect ratio, advancing water contact angles of 167° were measured with a water contact angle hysteresis of below 5°.

Keywords: Superhydrophobicity; Surface texturing; Topography; Embossing; Thermoplastic; Thermal imprinting; Aspect ratio; Laser interference lithography

Preparation and characterization of amine-functionalized SiO₂/TiO₂ films for formaldehyde degradation by Somjate Photong; Virote Boonamnuayvitaya (pp. 9311-9315).

This paper investigated the gaseous formaldehyde degradation by the amine-functionalized SiO₂/TiO₂ photocatalytic films for improving indoor air quality. The films were synthesized via the co-condensation reaction of methyltrimethoxysilane (MTMOS) and 3-aminopropyltrimethoxysilane (APTMS). The physicochemical properties of prepared photocatalysts were characterized with N₂ adsorption/desorption isotherms measurement, X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FT/IR). The effect of amine-functional groups and the ratio of MTMOS/APTMS precursors on the formaldehyde adsorption and photocatalytic degradation were investigated. The results showed that the formaldehyde adsorption and photocatalytic degradation of the APTMS-functionalized SiO₂/TiO₂ film was higher than that of SiO₂/TiO₂ film due to the surface adsorption on amine sites and the relatively high of the specific surface area of the APTMS-functionalized SiO₂/TiO₂ film (∼15 times higher than SiO₂/TiO₂). The enhancement of the formaldehyde degradation of the film can be attributed to the synergetic effect of adsorption and subsequent photocatalytic decomposition. The repeatability of photocatalytic film was also tested and the degradation efficiency was 91.0% of initial efficiency after seven cycles.

Keywords: Amine-functionalized SiO; ₂; /TiO; ₂; Photocatalyst; Formaldehyde; Titanium dioxide

Evolution of photo-catalytic properties of reactive plasma processed nano-crystalline titanium dioxide powder by M. Vijay; P.V. Ananthapadmanabhan; K.P. Sreekumar (pp. 9316-9322).

Nano-crystalline titanium oxide powder was synthesized by reactive plasma processing using titanium hydride as the precursor powder. Photo-catalytic properties of the product were evaluated by monitoring the degradation of methylene blue dye solution. The photo-catalytic activity of plasma-synthesized nano-sized titania powder could be enhanced considerably by incorporating surface Ti³⁺ sites and hydroxyl groups. Thermal treatment of the as-synthesized powder in flowing Ar–H₂ helped to incorporate surface Ti³⁺ and hydroxyl species, resulting in considerable increase in the catalytic activity. Subsequent hydrothermal treatment of the powder led to a five-fold increase in the photo-catalytic activity.

Keywords: Photo-catalysis; Reactive plasma processing; Nano-structure; Titanium dioxide; Arc plasma synthesis; Surface property

Synthesis and characterizations of AgSCN nanospheres using AgCl as the precursor by Ming Yang; Jing Ma (pp. 9323-9326).

Nanospheres of AgSCN with an average radius of 30–80nm have been prepared by a simple reaction between AgCl suspension and KSCN in the presence of gelatin. Gelatin played a decisive role as an inhibitor of the direct attack of SCN⁻ ions to AgCl surfaces and coagulation of the growing AgSCN in producing the spherical AgSCN nanoparticles. The products were characterized by X-ray powder diffraction, transmission electron microscopy and X-ray photoelectron spectra techniques. The electrical conductivity of thin films of as-prepared AgSCN nanoparticles and polyethylene oxide (PEO) at room temperature was measured. The maximum value of electrical conductivity of as-prepared AgSCN–PEO was 1.53×10⁻⁵Scm⁻¹.

Keywords: Silver thiocyanate; Nanospheres; Ion conductor

Synthesis, characterization and evaluation of uniformly sized core–shell imprinted microspheres for the separation trans-resveratrol from giant knotweed by Zhaohui Zhang; Li Liu; Hui Li; Shouzhuo Yao (pp. 9327-9332).

A novel core–shell molecularly imprinting microspheres (MIMs) with trans-resveratrol as the template molecule; acrylamide (AA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker, was prepared based on SiO₂ microspheres with surface imprinting technique. These core–shell trans-resveratrol imprinted microspheres were characterized by infrared spectra (IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and high performance liquid chromatography (HPLC). The results showed that these core–shell imprinted microspheres, which take on perfect spherical shape with average shell thickness of 150nm, exhibit especially selective recognition for trans-resveratrol. These imprinted microspheres were applied as solid-phase extraction materials for selective extraction of trans-resveratrol from giant knotweed extracting solution successfully.

Keywords: Surface imprinting; Core–shell; Microspheres; Trans-resveratrol

The role of etched silicon channels on the pore ordering of mesoporous silica: The importance of film thickness on providing highly orientated and defect-free thin films by Donna C. Arnold; John M. O’Callaghan; Aoife Sexton; Joseph M. Tobin; Heinz Amenitsch; Justin D. Holmes; Michael A. Morris (pp. 9333-9342).

If mesoporous thin films (MTFs) are to be utilised in device applications it is important that we produce films which not only possess a single pore direction across large substrate areas (in the range of microns) but are also relatively defect free. In this paper we report the use of confining architectures in the form of topographically patterned rectangular section channels etched into native silicon substrates to promote ordering of the mesopores. We discuss the effects of the channels on films with different thicknesses. The film thickness is shown to be a critical parameter in defining highly orientated and defect-free films and the data demonstrate that it is possible to achieve a single mesoporous silica domain across macroscopic dimensions with thin film thicknesses of approximately 200nm but that critically pore order can be lost in ultra thin and thicker films produced by these methods.

Keywords: Mesoporous silica; Thin films; Confining architectures; SAXS; XRR

Metallic glass coating on metals plate by adjusted explosive welding technique by W.D. Liu; K.X. Liu; Q.Y. Chen; J.T. Wang; H.H. Yan; X.J. Li (pp. 9343-9347).

Using an adjusted explosive welding technique, an aluminum plate has been coated by a Fe-based metallic glass foil in this work. Scanning electronic micrographs reveal a defect-free metallurgical bonding between the Fe-based metallic glass foil and the aluminum plate. Experimental evidence indicates that the Fe-based metallic glass foil almost retains its amorphous state and mechanical properties after the explosive welding process. Additionally, the detailed explosive welding process has been simulated by a self-developed hydro-code and the bonding mechanism has been investigated by numerical analysis. The successful welding between the Fe-based metallic glass foil and the aluminum plate provides a new way to obtain amorphous coating on general metal substrates.

Keywords: Explosive welding; Metallic glasses; Coating materials; Computer simulations

Calculation of the surface energy of hcp-metals with the empirical electron theory by Bao-Qin Fu; Wei Liu; Zhi-Lin Li (pp. 9348-9357).

A brief introduction of the surface model based on the empirical electron theory (EET) and the dangling bond analysis method (DBAM) is presented in this paper. The anisotropy of spatial distribution of covalent bonds of hexagonal close-packed (hcp) metals such as Be, Mg, Sc, Ti, Co, Zn, Y, Zr, Tc, Cd, Hf, and Re, has been analyzed. And under the first-order approximation, the calculated surface energy values for low index surfaces of these hcp-metals are in agreement with experimental and other theoretical values. Correlated analysis showed that the anisotropy of surface energy of hcp-metals was related with the ratio of lattice constants ( c/ a). The calculation method for the research of surface energy provides a good basis for models of surface science phenomena, and the model may be extended to the surface energy estimation of more metals, alloys, ceramics, and so on, since abundant information about the valence electronic structure (VES) is generated from EET.

Keywords: Surface energy; Empirical electron theory; Valence electron structure; Dangling bond; Hcp-metals

Effect of fluorine doping on highly transparent conductive spray deposited nanocrystalline tin oxide thin films by A.V. Moholkar; S.M. Pawar; K.Y. Rajpure; C.H. Bhosale; J.H. Kim (pp. 9358-9364).

The undoped and fluorine doped thin films are synthesized by using cost-effective spray pyrolysis technique. The dependence of optical, structural and electrical properties of SnO₂ films, on the concentration of fluorine is reported. Optical absorption, X-ray diffraction, scanning electron microscope (SEM) and Hall effect studies have been performed on SnO₂:F (FTO) films coated on glass substrates. The film thickness varies from 800 to 1572nm. X-ray diffraction pattern reveals the presence of cassiterite structure with (200) preferential orientation for FTO films. The crystallite size varies from 35 to 66nm. SEM and AFM study reveals the surface of FTO to be made of nanocrystalline particles. The electrical study reveals that the films are degenerate and exhibit n-type electrical conductivity. The 20wt% F doped film has a minimum resistivity of 3.8×10⁻⁴Ωcm, carrier density of 24.9×10²⁰cm⁻³ and mobility of 6.59cm²V⁻¹s⁻¹. The sprayed FTO film having minimum resistance of 3.42Ω/cm², highest figure of merit of 6.18×10⁻²Ω⁻¹ at 550nm and 96% IR reflectivity suggest, these films are useful as conducting layers in electrochromic and photovoltaic devices and also as the passive counter electrode.

Keywords: FTO thin films; Spray pyrolysis; Van der Pauw technique; X-ray diffraction

Tuning the morphology of mesoporous silica by using various template combinations by Li Du; Huiyu Song; Shijun Liao (pp. 9365-9370).

By using different dual-template combinations, four types of mesoporous silica materials with different morphologies were successfully synthesized. A solid-sphere mesoporous (SSM) silica was obtained using a combination of tri-block copolymer (F127) and 1,12-diaminododecane (DADD), but when F127 was substituted with poly(vinylpyrrolidone) (PVP), a leaf-shaped mesoporous (LSM) silica was obtained. In addition, a hollow-sphere mesoporous (HSM) silica was obtained by using a combination of PVP and dodecylamine (DDA), but a cotton-like mesoporous (CLM) silica was obtained using F127 instead of PVP. All four types of synthesized materials were characterized by SEM, TEM, XRD, and N₂ adsorption–desorption isotherms, and the results showed that all of them exhibited high surface area, large pore volume, worm-like pore structure, and beautiful shapes. The results of storage experiments revealed that the HSM and CLM showed good adsorption and storage properties. The HSM (the largest pore volume) seemed to have the larger storage capacity when compared to the CLM, albeit CLM had the highest surface area among all.

Keywords: Mesoporous silica; Morphology; Dual templates; Storage property

Ferromagnetism and microstructure in Fe⁺-implanted ZnO by D. Wang; Z.Q. Chen; F. Zhou; W. Lu; M. Maekawa; A. Kawasuso (pp. 9371-9375).

Fe ions were implanted into ZnO single crystals with multiple energies between 50 and 380keV up to a total fluence of12.5×1017cm⁻². The crystal quality of Fe⁺ implanted ZnO was investigated by X-ray diffraction2θ scans andω-rocking curve measurements. The appearance of Fe related diffraction peaks after700° C annealing of the implanted sample indicates possibly formation of Fe nanoparticles. Superconducting quantum interference device measurements revealed ferromagnetic behavior below 250K for both the as-implanted and post-annealed ZnO. Photoluminescence and Raman scattering as well as X-ray rocking curve measurements all indicate introduction of structural defects after Fe implantation. Some of the defects act as nonradiative recombination centers, and suppress the visible and ultraviolet (UV) emission in ZnO. These defects also break the Raman selection rule, and lead to the activation of some silent phonon modes. Annealing of the implanted sample at700° C causes partial recovery of the defects, however, the X-ray diffraction results of the anneal ZnO show even an improvement of the crystal quality compared with the un-implanted one. This could be attributed to the recovery of the grown-in defects in ZnO.

Keywords: ZnO; Implantation; Ferromagnetism; Defect

Effect of S- and Sn-doping to the optical properties of ZnO nanobelts by Ramin Yousefi; Burhanuddin Kamaluddin (pp. 9376-9380).

In this study, the optical properties of S- and Sn-doped ZnO nanobelts, grown by thermal evaporation, were investigated. The sulfur and tin contents in the nanobelts were about 12% and 8% (atomic), respectively. The average widths of the S- and Sn-doped ZnO nanobelts were 73 and 121nm, respectively. Room temperature photoluminescence (PL) spectroscopy exhibits significantly different optical properties for the two types of nanobelts. The PL result of the S-doped ZnO nanobelts shows the broad visible emission with no detectable ultraviolet (UV) peak, while the PL result of the Sn-doped sample shows two emission bands, one related to UV emission with a strong peak at 376nm that is blue-shifted by 4nm in comparison to pure ZnO nanobelts, and another related to green emission with a weak peak. A weak peak in the UV region at 383nm appeared after annealing the S-doped ZnO nanobelts at 600°C. Additionally, the annealed S-doped nanobelts show a stronger peak in the visible emission region in comparison to that observed prior to annealing. The Sn-doped ZnO nanobelts are also affected by annealing, as the UV emission peak is blue-shifted to 372nm after annealing.

Keywords: PACS; 73.20.Hb; 78.55.EtS-doped ZnO nanobelts; Sn-doped ZnO nanobelts; Optical properties; Annealing; Photoluminescence

Surface modification of M-Ba-ferrite powders by polyaniline: Towards improving microwave electromagnetic response by Xin Tang; Yuanguang Yang (pp. 9381-9385).

A composite of polyaniline (PANI)-coated M-type hexagonal barium ferrite (M-Ba-ferrite) powder was prepared by an in situ polymerization of an aniline monomer in the presence of M-Ba-ferrite particles. The obtained composite was characterized by Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The structure and microwave response properties were investigated. The continuous coverage of polyaniline has been produced on the platelet M-Ba-ferrite particle surface, and a core–shell structure has been formed. The results show that the coverage of polyaniline has a great influence on microwave response of M-Ba-ferrite particles. A polyaniline thin layer formed on the surface of a barium ferrite particle changes the character of frequency dispersion of microwave absorption. The results indicate the existence of an interaction at the interface of polyaniline macromolecule and barium ferrite particle, which influences the physical and chemical properties of the composite. The interaction and interfacial polarization are seen as important factors contributing to the influence on microwave response of the PANI-coated ferrite composite powders.

Keywords: Polyaniline; M-Ba-ferrite; Composite powders; Microwave absorption

Self-assembly of Ag nanopowder on OTS-patterned glass by Jae-hyun Kim; Bo-hyun Lee; Hansaem Kang; Jaeyeal Kim; Geesung Chae; Inbyeong Kang; In-jae Chung (pp. 9386-9390).

Ag ink was spontaneously patterned on glass substrate by using the surface energy difference of a pre-patterned octadecyltrichlorosilane (OTS) layer. Ag ink was confined into the hydrophilic area, where OTS layer was not formed. OTS layer was selectively transferred by micro-contact printing (μCP) method and significantly decreased surface energy. As a result, surface of glass substrate was separated as hydrophobic and hydrophilic with and without OTS layer, respectively. Ag line could be successfully patterned with the width of below 10μm on the glass. The patterned Ag line was dense and abrupt on the edge and the thickness was about 0.25μm. Ag film showed good adhesion on a glass substrate after anneal above 200°C. The minimum resistivity was about 4μΩcm.

Keywords: PACS; 81.07.Wx; 81.16.Dn; 81.07.PrSelf-assembly; Nanopowder; Solution process; Metal line

Effect of DC bias on microstructural rearrangement of a-SiN:H films on PET substrate by Bibhu P. Swain; Bhabani S. Swain; Nong M. Hwang (pp. 9391-9395).

Hydrogenated amorphous silicon nitride (a-SiN:H) films were deposited on flexible polyethylene terephthalate substrates at temperature as low as 100°C by hot-wire chemical vapor deposition using SiH₄, H₂ and NH₃ precursors. Field emission scanning emission microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy and small angle X-ray scattering were employed to study structural and microstructural properties of a-SiN:H films. The rms surface roughness increased with increase of positive bias to substrate. Intermediate range order, porosity and interface inhomogeneity in amorphous of a-SiN:H films evaluated by acoustic and optical phonon of silicon network, Guinier plot and correlated length from Raman and SAXS characterizations. The fractal behavior of a-SiN:H domains approached the perfect symmetry and the intermediate range order of a-SiN:H films deteriorate with increase of the positive substrate bias. Both correlation length and void size of the a-SiN:H amorphous domain increased with increase of the substrate bias from 0 to +200V.

Keywords: a-SiN:H; HWCVD; SAXS; Raman; FESEM

Laser melting of carbide tool surface: Model and experimental studies by B.S. Yilbas; S.Z. Shuja; S.M.A. Khan; A. Aleem (pp. 9396-9403).

Laser controlled melting is one of the methods to achieve structural integrity in the surface region of the carbide tools. In the present study, laser heating of carbide cutting tool and temperature distribution in the irradiated region are examined. The phase change process during the heating is modeled using the enthalpy–porosity method. The influence of laser pulse intensity distribution across the irradiated surface ( β) on temperature distribution and melt formation is investigated. An experiment is carried out and the microstructural changes due to laser consecutive pulse heating is examined using the scanning electron microscope (SEM). It is found that melt depth predicted agrees with the experimental results. The maximum depth of the melt layer moves away from the symmetry axis with increasing β.

Keywords: Laser; Melting; Tool; Carbide

Modeling of H₂O adsorption-induced curvature of a metal/silicon nanocantilever by Hong Yu; Qing-An Huang; Xiao-Xiao Liu (pp. 9404-9408).

A model to calculate the curvature of H₂O adsorption-induced bending for a metal/silicon nanocantilever is proposed based on atomic and molecular interaction. Part of the potential of both adsorbates and substrate transfers to the elastic energy of the cantilever, and the total energy of the system reaches a minimum value when adsorption is stable. According to this principle the model is developed to calculate H₂O adsorption-induced curvature of the nanocantilever. The model was tested with the molecular dynamics method using Material Studio software. The results agree with theoretical value. This model gives us a simple method to calculate adsorption-induced bending of the nanocantilever.

Keywords: PACS; 62.25.+gAdsorption; Potential; Nanocantilever; Stress

Characterization of microstructures induced in the workpiece of aluminum alloy by excimer laser micromachining by Ye Wu; Irene Ling Li; Ling Fu; Jian pang Zhai; Shuang Chen Ruan (pp. 9409-9412).

Excimer laser emitting at 248nm is applied to produce microstructures on the surface of aluminum alloy. The surface morphology shows that hotspots and thermal fluidic structures both come to light. Two possible mechanisms of hotspots formation are proposed: near-field diffraction and interference, and extremely fast rapid thermal annealing. And for the formation of thermal fluidic pattern structure, a thin film model is applied.

Keywords: Excimer laser micromachining; Aluminum

The microstructure, optical, and electrical properties of sol–gel-derived Sc-doped and Al–Sc co-doped ZnO thin films by Jianlin Chen; Ding Chen; Jianjun He; Shiying Zhang; Zhenhua Chen (pp. 9413-9419).

Transparent conductive ZnO:Al–Sc (1:0.5, 1:1, 1:1.5at.% Al–Sc) thin films were prepared on glass substrates by sol–gel method. The microstructure, optical, and electrical properties of ZnO:Sc and ZnO:Al–Sc films were investigated. Results show that Sc-doping alone obviously decreases grain size and degrades the crystallinity; there is an amorphous phase on the surface of ZnO grains; the transmittance spectra fluctuate dramatically with a large absorption valley at about 430–600nm. However, Al–Sc co-doping can stabilize grain size and improve the microstructure; an average visible transmittance of above 73% is obtained with no large absorption valley; the amorphous phase does not appear. The optical band gaps of ZnO:Sc and ZnO:Al–Sc films (3.30–3.32eV) are blue-shifted relative to pure ZnO film (3.30eV). Hall effects show that the lowest resistivity of 2.941×10⁻²Ωcm and the maximum Hall mobility of 24.04cm²/Vs are obtained for ZnO:Al–Sc films while ZnO:Sc films do not exhibit any electrical conductivity. Moreover, there is an optimum atomic ratio with Al to Sc of 1:0.5–1at.%. Although the resistivities are increased compared with that of ZnO:Al film, the Hall mobilities are raised by one order of magnitude.

Keywords: PACS; 81.20.Fw; 73.61.Ga; 64.70.NdTransparent conductive oxide; Thin film; Zinc oxide; Aluminum; Scandium; Doping

Influence of oxygen growth pressure on laser ablated Cr-doped In₂O₃ thin films by N.B. Ukah; R.K. Gupta; P.K. Kahol; K. Ghosh (pp. 9420-9424).

We present a systematic investigation of the effects of oxygen growth pressure on the structural, optical, and electrical properties of In₂O₃:Cr thin films grown by pulsed laser deposition. X-ray diffraction analysis showed increases in lattice constant from 10.103Å to 10.337Å, and in particle size from 13.9nm to 35.5nm as the oxygen growth pressure increased from 7.5×10⁻⁶Torr to 7.5×10⁻³Torr, respectively. The observed shift in the X-ray diffraction peaks to lower angles was assumed to be caused by the reduction in the lattice defect density, precisely oxygen vacancies. The optical transparency increased with partial oxygen pressure(PO2), and an average transmittance of ∼85% was obtained at 7.5×10⁻³Torr. The films are highly conducting with resistivity as low as 2×10⁻⁴Ωcm and mobility as high as 133cm/Vs. Temperature dependent resistivity measurements in the 45< T<300K temperature range reveal that films grown at7.5×10−6≤PO2≤7.5×10−4Torr exhibit negative temperature coefficient of resistivity (TCR) below approximately T=60K, T=120K, T=160K; then positive TCR in the temperature intervals 60< T<300K, 120< T<300K, and 160< T<300K, respectively. This suggests that two disparate mechanisms govern electrical dc transport in the two temperature regions. Film grown atPO2 of 7.5×10⁻³Torr displayed typical semiconducting behavior with negative TCR in the whole temperature region.

Keywords: Indium oxide; Chromium; Transparent conductor; Mobility

Effect of the Si/Ce molar ratio on the textural properties of rare earth element cerium incorporated mesoporous molecular sieves obtained room temperature by Qian Zhao; Yehai Xu; Yanhui Li; Tingshun Jiang; Changsheng Li; Hengbo Yin (pp. 9425-9429).

Rare earth Ce-incorporated MCM-41 mesoporous molecular sieves (CeMCM-41) were synthesized via a direct and nonhydrothermal method at room temperature from sodium silicate and ammonium cerium (IV) nitrate as raw materials. Cetyltrimethyl ammonium bromide (CTAB) was used as a template. The resultant samples were characterized by means of powder X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance ultraviolet–visible spectroscopy (UV–vis) and N₂ physical adsorption, respectively. The effect of the Si/Ce molar ratio on the crystalline structure and textural properties of CeMCM-41 was also investigated. The experimental results show that ordered CeMCM-41 mesoporous molecular sieves were successfully synthesized at room temperature and the resultant mesoporous materials have specific surface areas in the range of 594–1369m²/g and average pore sizes in the range of ca. 2.5–2.8nm. It has been found that the structural properties are strongly related to the amounts of cerium incorporation. When the cerium content increased in the samples, the intensity of the peak (100) was gradually reduced, and the surface area and structural regularity were diminished.

Keywords: Ce-incorporated mesoporous molecular sieve; Room temperature; Synthesis; Characterization; Textural property

Fabrication and tribological properties of super-hydrophobic surfaces based on porous silicon by Y.H. Liu; X.K. Wang; J.B. Luo; X.C. Lu (pp. 9430-9438).

In the present work, super-hydrophobic surfaces based on porous silicon (PS) were constructed by the self-assembled molecular films and their tribological properties were investigated. A simple chemical etching approach was developed to fabricate PS with the certain rough microstructure surface, which can be observed by the environmental scanning electron microscopy (ESEM). The hydrocarbon and fluorocarbon alkylsilane molecular films were self-assembled on PS, which was confirmed by the X-ray photoelectron spectroscopy (XPS) measurement. In contrast to PS, the alkylsilane molecular films modified PS (mPS) were super-hydrophobic since the apparent water contact angle (CA) exceeded 160°. The tribological properties of PS and the mPS were investigated by a ball-on-disk tribometer during the processes of different sliding velocities and normal loads. The experimental results showed that the alkylsilane molecular films could decrease the friction coefficient. Due to the difference of chain structure and functional groups, the fluorinated alkylsilane films are better candidates for improving the hydrophobicity and lubricating characteristics of PS comparing to the non-fluorinated ones. The carbon chain length of alkylsilane molecules self-assembling on the Si or PS substrates could have little effects on the hydrophobic properties and the tribology performances.

Keywords: Porous silicon; Alkylsilane molecular films; Super-hydrophobic; Tribological properties

Effect of gamma irradiation on the optical properties of nano-crystalline InP thin films by M.M. El-Nahass; A.A.M. Farag; F. Abd-El-Salam (pp. 9439-9443).

Thin films of InP were prepared onto glass and quartz substrates using laser ablation technique. Some of the prepared films were irradiated using a⁶⁰Co γ -ray source irradiation with a total dose of 100kGy at room temperature. The as deposited and irradiated films were identified by scanning electron microscopy, SEM and X-ray diffraction, XRD. The SEM images have shown a nano-flower like structure for the as deposited films and influenced by the irradiation dose. The Optical characterizations of the as deposited and irradiated InP films were studied using spectrophotometric measurements of transmittance T( λ) and reflectance, R( λ) at normal incidence of light in the spectral range from 200nm to 2500nm. The refractive index, n, and the absorption index, k values were calculated using a modified computer program based on minimizing (Δ T)² and (Δ R)² simultaneously, within the desired accuracy. Analysis of the dispersion of the refractive index in the range 900≤ λ≤2500 was discussed in terms of the single oscillator model. The optical parameters, such as the dispersion energy, E_d, the oscillator energy, E_o, the high frequency dielectric constant, ɛ_∞ and the lattice dielectric constant, ɛ_L were evaluated for the as deposited and irradiated films. The allowed optical transitions were found to be direct for the as deposited and irradiated films with energy gaps of 1.35eV and 1.54eV, respectively.

Keywords: Irradiation; InP; Nanocrystalline; Optical properties

Synthesis of self-assembly BaTiO₃ nanowire by sol–gel and microwave method by Chunlin Fu; Wei Cai; Longlong Zhou; Huaqiang Chen; Zhirong Liu (pp. 9444-9446).

Self-assembly ferroelectric BaTiO₃ nanowires were fabricated using sol–gel and microwave method. The X-ray diffraction patterns show that BaTiO₃ nanowires belong to the tetragonal perovskite structure. An increase in the intensity of (110) peak was observed as the annealing time increased. The shape of BaTiO₃ nanowires microwave-annealed for different minutes was investigated using atomic force microscopy. It is found that nanowires of BaTiO₃ annealed for 2.5min are very clear-cut, orderly and almost uninterrupted. The height of nanowire is near to the film thickness. However, nanowires of BaTiO₃ annealed for 5min are lesser, shorter and lower, and the distances among these nanowires are wider and well-proportioned. The origin of the distinct differences due to the remotion of atoms obtained enough energy was discussed.

Keywords: Nanowire; Microwave; Sol–gel preparation; Ferroelectrics; Barium titanate

Surface plasmon resonance in nano-gold antimony glass–ceramic dichroic nanocomposites: One-step synthesis and enhanced fluorescence application by Tirtha Som; Basudeb Karmakar (pp. 9447-9452).

A single-step melt-quench in situ thermochemical reduction technique has been used to synthesize a new series of Au° nanoparticles embedded antimony glass–ceramic (K₂O–B₂O₃–Sb₂O₃–ZnO) dichroic nanocomposites. X-ray and selected area electron diffractions manifest growth of Au° nanoparticles along (200) planes. The particle sizes obtained from X-ray diffraction patterns are found to vary in the range 4–21nm. Dichroic behavior is attributed to the elliptical shape gold nanoparticles having aspect ratio 1.2, as observed from the transmission electron microscopy (TEM) images. The Au° nanoparticles exhibit surface plasmon resonance band (SPR) around 600nm, which experiences red-shifts with increasing Au concentration. These nanocomposites when co-doped with Sm₂O₃ and excited at 949nm, exhibit 2-fold intensification of 636nm red emission transition (⁴G_5/2→⁶H_9/2) due to SPR induced local field enhancement of Au° nanoparticles and are promising materials for display applications.

Keywords: PACS; 42.70.Ce; 42.70.−a; 73.20.Mf; 81.05.PjSurface plasmon resonance; Nano gold; Antimony glass–ceramic; Nanocomposite; Enhanced fluorescence

The influence of polychromic light on the surface of MDI based polyurethane elastomer by Dan Rosu; Constantin Ciobanu; Liliana Rosu; Carmen-Alice Teaca (pp. 9453-9457).

A polyurethane elastomer was synthesized starting from 4,4′ diphenylmethane diisocyanate and poly(ethyleneadipate)diol. Butylene glycol was used as chain extender. Surface properties after photo-degradation of the elastomer under the action of the radiation with λ>300nm was monitored by FT-IR spectroscopy and contact angle measurements. The quality of polymer surface was observed under optical microscope. The formation of photo-Fries rearrangement and Norrish II reaction products during irradiation was associated with the gloss loss (from 100% for non-irradiated sample to 27% after 200h irradiation time) and modification of wettability. There were also found significant modifications with irradiation time of both the glass transition temperature ( T_g decreases from 64°C for non-irradiated sample to 53°C after 200h irradiation) and the swelling coefficient (an increase from 1.2% up to 2.5% is observed after 200h irradiation).

Keywords: Polyurethane; UV-irradiation; FT-IR spectroscopy; Gloss; Contact angle; Glass transition temperature

Influence of argon/oxygen atmospheric dielectric barrier discharge treatment on desizing and scouring of poly (vinyl alcohol) on cotton fabrics by Shujing Peng; Zhiqiang Gao; Jie Sun; Lan Yao; Yiping Qiu (pp. 9458-9462).

The effect of argon/oxygen atmospheric dielectric barrier discharge (DBD) treatment on desizing and scouring of polyvinyl alcohol (PVA) on cotton fabric was studied with respect to the treatment duration of 1, 2, 4 and 6min. X-ray photoelectron spectroscopy (XPS) analysis indicated that oxygen concentration increased for the plasma treated PVA film. Solubility measurement revealed that plasma treatment increased PVA solubility in hot washing but less effective in cold washing. Scanning electron microscopy (SEM) showed that the fiber surfaces were as clean as unsized fibers after 6min treatment followed by hot washing. Wickability analysis indicated that the capillary heights of plasma treated fabrics increased significantly as the plasma treatment duration increased. The results of the yarn tensile strength test showed that the plasma treatment did not have a negative effect on fabric tensile strength.

Keywords: Dielectric barrier discharge; Polyvinyl alcohol; Desizing; Scouring; SEM; XPS

Controlled synthesis of pompon-like self-assemblies of Pd nanoparticles under microwave irradiation by Xia Tong; Yanxi Zhao; Tao Huang; Hanfan Liu; Kong Yong Liew (pp. 9463-9468).

Pd nanoparticles with uniform, self-assembled pompon-like nanostructure were synthesized by thermal decomposition of palladium acetate under microwave irradiation with methyl isobutyl ketone (MIBK) as a solvent in the presence of a little amount of ethylene glycol (EG) and KOH without using any special stabilizers. The as-synthesized Pd nano-pompons were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray powder diffraction. The results show that the as-prepared Pd nano-pompons with the average diameters in the range of 28–81nm were self-assemblies organized by hundreds of smaller primary nanoparticles with an average dimension of about 2.4nm. The sizes of Pd nano-pompons can be well controlled by adjusting the concentration of palladium acetate. A little amount of EG and KOH also plays an important role in controlling the size, uniformity and dispersion of Pd nano-pompons. The Pd nano-pompons can be easily supported on γ-Al₂O₃ and their catalytic activity was examined preliminarily.

Keywords: Pd; Palladium acetate; Methyl isobutyl ketone; Nano-pompon; Self-assembly; Microwave

Study on sapphire removal for thin-film LEDs fabrication using CMP and dry etching by Shengjun Zhou; Sheng Liu (pp. 9469-9473).

Mechanical grinding, chemical mechanical polishing (CMP) and dry etching process are integrated to remove sapphire substrate for fabricating thin-film light-emitting diodes. The thinning of sapphire substrate is done by fast mechanical grinding followed by CMP. The CMP can remove or reduce most of the scratches produced by mechanical grinding, recovering both the mechanical strength and wafer warpage to their original status and resulting in a smoother surface. The surface morphology and surface roughness on grinded and polished sapphire substrate are measured by using atomic force microscopy (AFM). The etch rates of sapphire by BCl₃-based dry etching are reported. Pattern transfer to the physical and chemical stability of sapphire is made possible by inductively coupled plasma (ICP) etch system that generates high density plasma. The patterning of several microns period in sapphire wafer by using a combination of BCl₃/Ar plasma chemistry and SiO₂ mask is presented. The anisotropic etch profile formed on sapphire wafer is obtained from scanning electron microscopy (SEM) images.

Keywords: Sapphire substrate; Mechanical grinding; CMP; Dry etching

Fabrication of cuprous and cupric oxide thin films by heat treatment by Ahalapitiya H. Jayatissa; K. Guo; Ambalangodage C. Jayasuriya (pp. 9474-9479).

Cuprous oxide (Cu₂O) and cupric oxide (CuO) thin films were prepared by thermal oxidation of copper films coated on indium tin oxide (ITO) glass and non-alkaline glass substrates. The formation of Cu₂O and CuO was controlled by varying oxidation conditions such as, oxygen partial pressure, heat treatment temperature, and oxidation time. The microstructure, crystal direction, and optical properties of copper oxide films were measured with X-ray diffraction, atomic force microscopy, and optical spectroscopy. The results indicated that the phase-pure Cu₂O and CuO films were produced in the oxidation process. Optical transmittance and reflectance spectra of Cu₂O and CuO clearly exhibited distinct characteristics related to their phases. The electrical properties indicated that these films formed ohmic contacts with Cu and ITO electrode materials. Multilayers of Cu₂O/CuO were fabricated by choosing the oxidation sequence. The experimental results in this paper suggest that the thermal oxidation method can be employed to fabricate device quality Cu₂O and CuO films that are up to 200–300nm thick.

Keywords: Cuprous oxide; Cupric oxide; Thermal oxidation; Optical transmittance; X-ray diffraction; Resistivity

The effect of cerium oxide argon-annealed coatings on the high temperature oxidation of a FeCrAl alloy by C.T. Nguyen; H. Buscail; R. Cueff; C. Issartel; F. Riffard; S. Perrier; O. Poble (pp. 9480-9486).

Ceria coatings were applied in order to improve the adherence of alumina scales developed on a model Fe–20Cr–5Al alloy during oxidation at high temperature. These coatings were performed by argon annealing of a ceria sol–gel coating at temperatures ranging between 600 and 1000°C. The influence of these coatings on the alloy oxidation behaviour was studied at 1100°C. In situ X-ray diffraction (XRD) was performed to characterize the coating crystallographic nature after annealing and during the oxidation process. The alumina scale morphologies were studied by means of scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS). The present work shows that the alumina scale morphology observed on cerium sol–gel coated alloy was very convoluted. On the cerium sol–gel coated alloy, argon annealing results in an increase of the oxidation rate in air, at 1100°C. The 600°C argon annealing temperature results in a good alumina scale adherence under thermal cycling conditions at 1100°C.

Keywords: FeCrAl alloy; Oxidation; Cerium; Sol–gel coating; Alumina; In situ X-ray diffraction

Adsorption of phenolic compounds from aqueous solutions using carbon nanoporous adsorbent coated with polymer by Mansoor Anbia; Arezoo Ghaffari (pp. 9487-9492).

Phenolic compounds are a widespread class of water pollutants that are known to cause serious human health problems; and the demand for effective adsorbents for the removal of toxic compounds is increasing.In this work adsorption of phenol, resorcinol and p-cresol on mesoporous carbon material (CMK-1) and modified with polyaniline polymer (CMK-1/PANI) has been investigated in attempt to explore the possibility of using nanoporous carbon as an efficient adsorbent for pollutants. It was found that CMK-1/PANI exhibits significant adsorption for phenolic derivatives. Batch adsorption studies were carried out to study the effect of various parameters like adsorbent dose, pH, initial concentration and contact time. From the sorption studies it was observed that the uptake of resorcinol was higher than other phenolic derivatives. Freundlich and Langmuir adsorption isotherms were used to model the equilibrium adsorption data for phenolic compounds.

Keywords: Adsorption; Mesoporous; Carbon; Phenol; Resorcinol; p-Cresol

Facile method to prepare stable superhydrophobic Co₃O₄ surface by Zhiqing Yuan; Hong Chen; Chao Li; Lianghui Huang; Xin Fu; Dejian Zhao; Jianxin Tang (pp. 9493-9497).

A facile and novel method was developed to fabricate rough Co₃O₄ surface with hierarchical micro- and nanostructures by the combination of simple solid state reactions and coating process. After modification with stearic acid, a superhydrophobic surface with water contact angle of 155±1.8° and sliding angle of 2° was obtained. The superhydrophobic Co₃O₄ surface remained superhydrophobic property in a wide pH range from 3 to 14. The superhydrophobic Co₃O₄ surface also showed excellent self-cleaning property and high stability in ambient environments.

Keywords: Superhydrophobic surface; Co; ₃; O; ₄; Contact angle; Sliding angle

Microstructure, optical and electrical properties of nitrogen doped sp²-rich a-C thin films grown by facing-target magnetron sputtering by J.Q. Wu; X.C. Wang; E.Y. Jiang; H.L. Bai (pp. 9498-9503).

N atoms were incorporated into sp²-rich a-C networks using DC facing-target reactive sputtering at various N₂ fraction (PN2) and their structure and opto-electrical properties were investigated systematically. AsPN2 increases, the fraction of CN bonded carbons (or the N content) increases primarily at the expense of the CC bonded carbons and then reaches its saturated value atPN2>40%. The incorporated N preferentially forms different kinds of non-aromatic CN phase, leading to more localization of π electrons and the loss of the connectivity of nanographite fragments in the films, which is different from the case in N-doped sp³-rich a-CN_x films. Hence, with increasingPN2, the a-C(:N) film converts from a semiconductor with a narrower optical band gap to an insulator-like material with a wider gap. Additionally, the variation of optical constants ( n and k) and spin defects are related to the enhancement of the non-aromatic CN phase.

Keywords: PACS; 81.15.Cd; 61.43.Dq; 81.05.Uw; 78.66.Jg; 73.61.Jc; 71.55.JvMagnetron sputtering; Amorphous carbon nitride; Optical properties; Electrical properties; Defects

Formation of antireflection nanostructure for silicon solar cells using catalysis of single nano-sized silver particle by Kensuke Nishioka; Tsuyoshi Sueto; Nobuo Saito (pp. 9504-9507).

Antireflection nanostructure was formed by simple wet chemical etching using catalysis of silver (Ag) nanoparticle. Single nano-sized Ag particle dispersion solution was coated onto Si(100) substrate with polished surface. Then, the samples were soaked in an aqueous etching solution of hydrofluoric acid and hydrogen peroxide. The surface of 9-min-etched Si substrate appeared black, and the reflectivity was reduced to below 5% throughout the entire spectrum from 200 to 1000nm owing to the formed nanostructure. The absorption was significantly increased after the formation of antireflection structure with 9min etching, and the conversion efficiency of solar cell with antireflection structure increased from 8.25 to 10.0% owing to the increase of short-circuit current.

Keywords: Silicon; Nanostructure; Silver; Catalysis; Single nano-sized particle; Antireflection; Solar cell

Synthesis of Cr₂O₃/TNTs nanocomposite and its photocatalytic hydrogen generation under visible light irradiation by Yao Jun Zhang; Ya Chao Wang; Wei Yan; Tuo Li; Sheng Li; Ya Ru Hu (pp. 9508-9511).

A novel Cr₂O₃/TNTs nanocomposite was prepared by loaded suitable amount of amorphous Cr₂O₃ on titanate nanotubes (TNTs) via hydrothermal reaction and impregnation process. XRD, SEM and TEM results demonstrated that the amorphous Cr₂O₃ nanoparticles were homogeneously dispersed on the surface of TNTs. The diffuse reflectance UV–visible absorption spectra exhibited that the spectral response of TNTs was extended to visible light region by coupled with Cr₂O₃. The 2.5Cr₂O₃/TNTs nanocomposite showed the highest activity of hydrogen generation by photocatalytic water-splitting under visible light irradiation ( λ>400nm). The high activity of H₂ evolution for Cr₂O₃/TNTs nanocomposites was associated with the donor level in the forbidden band of TNTs semiconductor provided by dopant Cr³⁺ and a probably photocatalytic mechanism was proposed.

Keywords: Nanocomposite; Hydrogen production; Water-splitting; Photocatalysis

Laser welding of aluminium alloys 5083 and 6082 under conduction regime by J.M. Sánchez-Amaya; T. Delgado; L. González-Rovira; F.J. Botana (pp. 9512-9521).

In this work, samples of aluminium alloys 5083-T0 and 6082-T6 have been welded under conduction regime, using a high power diode laser. The influence of experimental variables, as the laser power and the linear welding rate, on the sizes and properties of the butt weld beads has been studied. In addition to measure the depths and widths of the weld beads, their microstructure, microhardness profile and corrosion resistance have been analysed. The results obtained allow one to define the experimental conditions leading to good quality butt welds with higher penetration than those published in the recent literature under conduction regime. Maximum penetration values of 3 and 2.3mm were obtained for 5083 and 6082, respectively. Additionally, a simple mathematical expression relating the weld depth ( d) with the laser power ( P) and the processing rate ( v) has been proposed:d=(P−bb′)/(av)−(ba′)/a, being a, a′, b and b′ constant values for each alloy and under the employed experimental conditions. The values of these coefficients have been estimated from the fitting to the experimental depth values of 5083 and 6082 butt welds generated under conduction regime.

Keywords: Laser welding; Aluminium alloys; Conduction regime; Depth estimation; Corrosion resistance

Influence of growth pressure on the electrical properties of boron-doped polycrystalline diamond films by Z.L. Wang; C. Lu; J.J. Li; C.Z. Gu (pp. 9522-9525).

Heavily boron-doped diamond films are synthesized by the hot-filament chemical vapor deposition method under the gas mixtures of H₂, CH₄ and trimethyl borate. The measurement results of scanning electron microscopy, Raman spectroscopy, X-ray diffractometer and electrical properties showed the morphologies, microstructures, carrier concentration and superconducting transition temperature for as-grown diamond films were dependent on the change of growth pressure, and specially its carrier concentrations could be adjusted from 10¹⁹ to 10²¹cm⁻³ by increasing growth pressures from 2.5 to 5kPa. And further, the effects of growth pressure on the film microstructural property and the doping level dependence of the superconducting transition temperature were discussed.

Keywords: Boron-doped diamond films; Superconductivity; HFCVD

Quinoline group grafted carbon nanotube fluorescent sensor for detection of Cu²⁺ ion by Zhengping Dong; Jun Jin; Wenfeng Zhao; Huamei Geng; Ping Zhao; Rong Li; Jiantai Ma (pp. 9526-9530).

A carbon nanotube-based fluorescent chemosensor MWNTs-glycine-N-8-quinolylamide (MWNTs-GNQ) has been designed and synthesized. Steady-state fluorescence emission studies showed that this material displays high selectivity and sensitivity for the Cu²⁺ ion over other cations such as Zn²⁺, Cd²⁺, Mg²⁺, Ca²⁺, and Ni²⁺.

Keywords: Carbon nanotubes; Glycine-N-8-quinolylamide; Cu; ²⁺; ion; Detection

The mechanism of PEO process on Al–Si alloys with the bulk primary silicon by Fangtao Xu; Yuan Xia; Guang Li (pp. 9531-9538).

This study focuses on mechanism of ceramic coating on Al–Si alloys with bulk primary Si using plasma electrolytic oxidation (PEO) technology. Al–Si alloys with 27–32%Si in weight were used as substrates. The morphologies, composition and microstructure of PEO coatings were investigated by scanning electron microscopy (SEM) with energy dispersive X-ray system (EDX). Results showed that the PEO process had four different stages. The effect of bulk Si is greatly on the morphology and composition of coatings at first three stages. Anodic oxide films formed on Al and Si phases, respectively. When the voltage exceeded 40V, glow appeared and concentrated on the localized zone of interface of Al and Si phase. Al–Si–O compounds formed and covered on the dendrite Si phase surface, and the coating on bulk Si, which was silicon oxide, was rougher than that on other phase. If the treatment time was long enough, the coatings with uniform surface morphologies and elements distribution will be obtained but the microstructure of inner layer is looser due to the bulk Si.

Keywords: PEO; Al–Si alloys; Bulk primary silicon; Dentrite silicon

Thermal decomposition of bioactive sodium titanate surfaces by Matthieu Ravelingien; Steven Mullens; Jan Luyten; Vera Meynen; Evi Vinck; Chris Vervaet; Jean Paul Remon (pp. 9539-9542).

Alkali-treated orthopaedic titanium surfaces have earlier shown to induce apatite deposition. A subsequent heat treatment under air improved the adhesion of the sodium titanate layer but decreased the rate of apatite deposition. Furthermore, insufficient attention was paid to the sensitivity of titanium substrates to oxidation and nitriding during heat treatment under air. Therefore, in the present study, alkali-treated titanium samples were heat-treated under air, argon flow or vacuum. The microstructure and composition of their surfaces were characterized to clarify what mechanism is responsible for inhibiting in vitro calcium phosphate deposition after heat treatment. All heat treatments under various atmospheres turned out to be detrimental for apatite deposition. They led to the thermal decomposition of the dense sodium titanate basis near the interface with the titanium substrate. Depending on the atmosphere, several forms of Ti_yO_z were formed and Na₂O was sublimated. Consequently, less exchangeable sodium ions remained available. This pointed to the importance of the ion exchange capacity of the sodium titanate layer for in vitro bioactivity.

Keywords: Titanium; Alkali treatment; Sodium titanate; Bioactivity; Thermal properties

Nitridation of organo-silicate glass: A self-limiting process for PVD Ta1+_xN/Ta barrier formation by J.A. Wilks; J.A. Kelber (pp. 9543-9547).

Interfacial reactions of sputter-deposited Ta with a low dielectric constant Si–O–C–H material (SiCOH), and with surface-nitrided SiCOH (N-SiCOH) were investigated using X-ray photoelectron spectroscopy (XPS). The studies were carried out in a system containing a processing chamber attached to an XPS analysis chamber so that sample transport between deposition and analysis environments occurred under ultrahigh vacuum (UHV) conditions. Ta sputter deposition on unmodified SiCOH yielded an interfacial phase ∼3nm thick composed of Ta oxide/carbide (Ta–O–C), which is known to interact only weakly with Cu. Bombardment of the vicinal SiCOH surface by 500eV Ar⁺ in the presence of NH₃ resulted in carbon depletion and the self-limiting nitridation of the surface, with N attachment primarily at Si sites. Subsequent Ta sputter deposition yielded reduced Ta oxide and carbide formation, and formation of a Ta-rich nitride layer of 10Å average thickness. Subsequent deposition resulted in metallic Ta formation.

Keywords: Diffusion barrier; Dielectrics; Physical vapor deposition (PVD); Tantalum; Tantalum nitride; Transmission electron microscopy; X-ray photoelectron spectroscopy (XPS)

Preparation of F-doped titania nanoparticles with a highly thermally stable anatase phase by alcoholysis of TiCl₄ by Yingying Lv; Leshu Yu; Heyong Huang; Hailong Liu; Yuying Feng (pp. 9548-9552).

Pure anatase is a metastable phase and inclined to (transform) be transformed into rutile structure under heating over than 500°C, which limits its suitability for high-temperature applications. Hitherto much research efforts have been made to increase the stability temperature of anatase structure. However, metallic doping usually introduced metallic oxides into titania at high temperature, and many nonmetallic doping are not competent for increasing the stability temperature of anatase structure up to 900°C. In this study, F-doped anatase TiO₂ nanoparticles were conveniently prepared via the alcoholysis of TiCl₄ and the as-prepared product shows very high stability temperature up to 1000°C before being transformed into rutile structure phase. On the basis of XPS results of F-doped titania annealed at different temperature, it is learned that the F atoms were anchored on the crystal planes of anatase in favor of decreasing the energy faces of anatase and stabilizing the anatase structure till annealed at 1300°C all the anatase were transformed into rutile phase.

Keywords: Ceramics; High-temperature alloys; Oxide materials; Sintering; Phase transitions; X-ray diffraction

Angle-dependent ultraviolet photoelectron spectroscopy of sputter cleaned polycrystalline noble metals by M.G. Helander; M.T. Greiner; Z.B. Wang; Z.H. Lu (pp. 9553-9556).

Polycrystalline noble metal films are commonly used in practical applications across a variety of different fields. However, the surface electronic structure of the noble metals has primarily only been studied on single crystal substrates. In addition, sputter cleaned polycrystalline noble metal films are commonly used substrates in ultraviolet photoelectron spectroscopy (UPS) studies, but have yet to be systematically studied in terms of their photoemission anisotropy. The angle-dependence of the valence band spectra of sputter cleaned polycrystalline Au, Ag and Cu were studied using angle-resolved UPS. It is found that the photoemission is anisotropic with respect to photoelectron take-off angle. The results for Ag and Cu are in good agreement with previous reports of surface d-band narrowing in polycrystalline noble metal films. However, significant anisotropies in the d-band, s-band and Fermi edge of sputter cleaned Au are observed, which cannot be attributed to surface d-band narrowing alone. The unusual results for Au are attributed to drastic changes in the film morphology near the surface as a result of sputter cleaning.

Keywords: Ultraviolet photoelectron spectroscopy; Polycrystalline films; Noble metals; Sputter cleaning; Valence band spectra; Angle-resolved photoemission

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Applied Surface Science (v.255, #23)

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Applied Surface Science (v.255, #23)