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Applied Surface Science (v.255, #18)

SLM-based maskless lithography for TFT-LCD by Kwang-Ryul Kim; Junsin Yi; Sung-Hak Cho; Nam-Hyun Kang; Myung-Woo Cho; Bo-Sung Shin; Byoungdeog Choi (pp. 7835-7840).

Maskless photolithographic methods have been developed using digital micromirror devices (DMDs) and grating light valves (GLVs), which are spatial light modulators (SLMs), because liquid crystal display (LCD) panel industries spend huge amounts of money for the cost of TFT (thin film resist)-LCD photomasks. The technology has been developed for implementing 2μm bitmap resolutions, which is a requirement for the lithographic process, though the process time is still slow for mass-production system. A DMD-based maskless exposure uses 405nm-wavelength semiconductor lasers as an illumination source and optical engines that contain DMDs, micro lens arrays (MLAs), and projection lenses. A GLV-based system consists of UV lasers and optical write engines, which are constructed with the GLV, grating optics, and imaging lenses. Since many companies have been trying to overcome the time limitations, the maskless technology will be realized in the LCD industry in near future.

Keywords: Spatial light modulator; Maskless lithography; DMD; GLV

Effect of humidity on subcritical crack growth of indentation crack under sustained electric field in PZT ceramics by L.W. Li; X. Sun; J.X. Li; L.J. Qiao; Y.J. Su; W.Y. Chu (pp. 7841-7845).

The effect of humidity on subcritical crack growth of indentation crack in lead zirconate titanate (PZT) ferroelectric ceramics under various sustained electric field has been investigated. The results showed that subcritical crack growth of indentation crack could occur in humid air of 60%RH without electric field but did not in air with RH≤30%. The subcritical crack growth could occur in vacuum under a sustained electric field of E/ E_C=0.14. The incubation time decreased and the amount of the subcritical crack growth increased with increasing the humidity under the sustained field. The threshold electric field for subcritical crack growth decreased with increasing the humidity.

Keywords: Humidity; Subcritical crack growth; Indentation crack; PZT ceramics

Fabrication of carbon nanoflowers by plasma-enhanced chemical vapor deposition by Xiying Ma; Baohe Yuan (pp. 7846-7850).

Two and three-dimensional (2D and 3D) carbon nanoflowers have been prepared on silicon (111) substrates by plasma-enhanced chemical vapor deposition, using CH₄, H₂ and Ar as reactive gases in the presence of Fe catalyst. The flower patterns are controlled by the flux ratio of the carrier gas, the reaction pressure and the growth temperature. Through observation by scanning electron microscopy, we find that the 2D carbon nanoflowers are formed by various nanoleaves while the 3D flowers are composed of hundreds of nanofibers. The former is related closely to the flux ratio of gas and the reaction pressure, while the latter depended mainly on the growth temperature. The nucleation and growth process of the nanoflowers seem to be a vapor/liquid/solid mechanism.

Keywords: PACS; 61.46+w; 61.48+cCarbon nanoflower; PECVD; SEM

Characteristic and microstructure of the microarc oxidized TiO₂-based film containing P before and after chemical- and heat treatment by Daqing Wei; Yu Zhou; Chunhui Yang (pp. 7851-7857).

Chemical- and heat treatment was performed to modify the surface of the microarc oxidized TiO₂-based (TOB) film containing P to produce nano-scale compounds containing Na, Ti and O elements. In the TOB film, anatase and rutile nanocrystals were randomly distributed in P-doped matrix. On the surface of the chemically treated TOB (C-TOB) film, amorphous titanium oxide containing Na shows nano-scale ribbonlike morphology. Na, Ti and O show uniform distribution in the outer layer of the C-TOB film along surface depth. Chemical treatment did not alter the surface roughness of the TOB film obviously; however, it improved its hydrophilic property. Heat treatment has no influence on the chemical states of Ti, Na and O, as well as wetting ability, elemental composition and atomic concentration in the outer layer of the C-TOB film. However, the phase compositions and surface morphology of the C-TOB film after heat treatment are dependent on the heat treatment temperature.

Keywords: Film; Titanium alloy; Amorphous; Titanium oxide; Microarc oxidation; Chemical and heat treatment

Effect of N content on phase configuration, nanostructure and mechanical behaviors in Ti–C_x–N_y thin films by Y.H. Lu; J.P. Wang; Y.G. Shen (pp. 7858-7863).

Ti–C_x–N_y thin films with different nitrogen contents were deposited by way of incorporation of different amounts of nitrogen into TiC_1.02 using unbalanced reactive unbalanced dc magnetron sputtering method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and microindentation methods were used to investigate their phase configurations, nanostructures and mechanical behaviors in order to investigate their dependences on nitrogen content. The result indicated that the nitrogen content had a significant effect on phase configuration, nanostructure and mechanical behaviors of Ti–C_x–N_y thin films. The nitrogen-free TiC_1.02 films exhibited a polycrystallite with nano-grains. On one hand, incorporated nitrogen substituted C in TiC_1.02, producing Ti(C,N), and subsequently linked to the substituted C, forming C–N. On the other hand, the substituted C lined to each other, forming C–C. As a result, nanocomposite thin films consisting of nanocrystalline Ti(C,N) and amorphous (C, C–N) were produced. With further incorporation of nitrogen more C was substituted, accompanying with formation of more amorphous matrices and decrease of size of nanocrystalline Ti(C,N). The trend was enhanced with further increase of nitrogen content. A microhardness maximum of ∼58GPa was obtained in nitrogen-free TiC_1.02 thin films. This value was linearly decreased with incorporation of N or increase of N content, and finally a hardness value of about 28GPa was followed at a N content of ∼25at.%. Both elastic modulus and residual compressive stress values exhibited similar trends.

Keywords: Hardness; Microstructure; Nanocomposite thin films; N content; Ti–C; _x; –N; _y

Characterization of copper SERS-active substrates prepared by electrochemical deposition by Jitka Cejkova; Vadym Prokopec; Sona Brazdova; Alzbeta Kokaislova; Pavel Matejka; Frantisek Stepanek (pp. 7864-7870).

Surface Enhanced Raman Scattering (SERS) on copper substrates of various morphologies, prepared by electrochemical deposition on platinum targets, was investigated. The substrate preparation procedures differed by the coating bath compositions, applied current densities and the duration of individual steps. The surface morphology of the substrates was visualized by means of Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). SERS spectra of selected organic thiols were measured and the relation between SERS spectral intensity and the surface structure of SERS-active substrates was studied. It has been shown that good Raman surface enhancement can be achieved on the copper substrates prepared by electrochemical deposition from ammoniac baths. Copper substrates fabricated from acidic baths did not show efficient Raman surface enhancement. The results of microscopic measurements demonstrated that the average surface roughness value does not play a substantial role, whereas the shape of the surface nanostructures is a key parameter.

Keywords: Surface Enhanced Raman Scattering (SERS); Atomic Force Microscopy (AFM); Scanning Electron Microscopy (SEM); Copper; Electrochemical deposition

Correlation between interfacial interactions and mechanical properties of PA-6 doped with surface-capped nano-silica by Deliang Li; Qing Liu; Laigui Yu; Xiaohong Li; Zhijun Zhang (pp. 7871-7877).

The polyamide-6 pellets were mixed with nano-SiO₂ particles surface-capped by 3-aminopropyltriethoxysilane (APS) via a melt blending route. PA-6 composites doped with surface-capped nano-SiO₂ (designated as PAMNS, where AMNS refers to APS surface-capped nano-SiO₂). AMNS and the silica samples (designated as EAMNS) extracted by acid etching from various PAMNS samples containing different concentration of amino functional groups on surface-capped nano-silica surfaces were characterized by means of Fourier transformation infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). This aims at revealing the interfacial interaction between AMNS and PA-6 matrix and its effect on the mechanical properties of the filled PA-6 composites. The chemical features and microstructures of the PAMNS composites were analyzed by means of FTIR and transmission electron microscopy (TEM), respectively, while their mechanical properties were evaluated using standardized test rigs. Results demonstrate that the surface-modified nano-SiO₂ particles were uniformly dispersed in PA-6 matrix. The residue silica extracted from various PAMNS samples showed characteristic FTIR absorbance peak of PA-6 and had larger weight losses than AMNS, implying that the polymeric matrix was chemically bonded with the nanofiller particles. The interfacial interactions are closely related to the concentration of functional groups in AMNS, and there might exist a critical concentration at which the strongest interfacial interactions could be reached. Beyond the critical concentration of the functional groups in AMNS, the mechanical properties of the filled PA-6 composites tended to decrease to some extent.

Keywords: Polyamide 6; Nano-SiO; ₂; Surface-capping; Interfacial interactions; Microstructure; Mechanical properties

Some aspects on 3D numerical modeling of high velocity impact of particles in cold spraying by explicit finite element analysis by Wen-Ya Li; Wei Gao (pp. 7878-7892).

Three-dimensional modeling of particle impacting behavior in cold spraying by using ABAQUS/Explicit was conducted for copper and other materials. Various combinations of calculation settings concerning material damage, Arbitrary Lagrangian Eulerian adaptive meshing, distortion control and contact interaction were examined. The effects of meshing size and particle size on the impact behavior were analyzed compared to the previous results. The results show that the simulations with material damage cope well with the element excessive distortion and the resultant output is more reasonable than that obtained without material damage. In addition, the meshing size has less effect on the output with the material damage than without material damage. Although particle size has little effect on the morphologies of the deformed particles, it has some effect on the failure of elements at contact interfaces. The critical velocity for particle deposition could be estimated given the appropriate material properties.

Keywords: Cold spraying; Finite element analysis; Copper; Impact behavior; High-speed deformation

Influence of phytic acid concentration on coating properties obtained by MAO treatment on magnesium alloys by R.F. Zhang; S.F. Zhang; S.W. Duo (pp. 7893-7897).

Anodic coatings were prepared by microarc oxidation (MAO) on AZ91HP in a base solution of 10g/L NaOH with and without the addition of 0–12g/L phytic acid (C₆H₁₈O₂₄P₆). The influences of C₆H₁₈O₂₄P₆ and its concentration on the conductivity and breakdown voltage were studied. The morphologies and compositions of anodic coatings were determined by environmental scanning electron microscope (ESEM) and energy dispersive X-ray spectroscopy (EDX). Potentiodynamic polarization test was performed in 3.5wt.% NaCl solution to evaluate the corrosion resistance of anodic coatings. The results showed that with the increase of C₆H₁₈O₂₄P₆ concentration, the solution conductivity decreased while the values of breakdown voltage increased. EDX analysis showed that the coatings formed in solutions with C₆H₁₈O₂₄P₆ addition contained Mg, Al, O, C, P and a trance of Na. The addition of C₆H₁₈O₂₄P₆ into the base solution was helpful in coating formation and the coatings formed in the solution containing 8g/L C₆H₁₈O₂₄P₆ exhibited the best pore uniformity and corrosion resistance.

Keywords: Magnesium alloy; MAO; Electrolyte; Phytic acid; Concentration

Electrostatic forces in micromanipulation: Experimental characterization and simulation including roughness by Enrico Tam; Marion Sausse Lhernould; Pierre Lambert; Alain Delchambre; Marie-Paule Delplancke-Ogletree (pp. 7898-7904).

Manipulation by contact of objects between 1μm and 1 mm are often disturbed by adhesion between the manipulated object and the gripper. Electrostatic forces are among the phenomena responsible for this adhesive effect. Analytical models have been developed in the literature to predict electrostatic forces. Most models have been developed within the framework of scanning probe microscopy, i.e. for a contact between a conducting tip and a metallic surface. In our study, we developed a simulation tool based on finite elements modeling. The strength of this model lies in the fact that it integrates roughness parameters. Measurements of electrostatic forces in function of roughness were conducted by atomic force microscopy. The experimental results were compared with the simulation results showing very good correlation. This demonstrates the influence of surface topography on electrostatic forces, especially for very small separation distances and proves the utility of the simulation tool in designing surfaces with controlled adhesion. Some application fields to which these results can be applied are drug delivery devices and micromanipulation tools.

Keywords: Micromanipulation; Adhesion; Electrostatic forces; Roughness; Fractals

Synthesis and field emission properties of carbon nanotubes grown in ethanol flame based on a photoresist-assisted catalyst annealing process by Xiaoxia Yang; Guojia Fang; Nishuang Liu; Chong Wang; Qiao Zheng; Hai Zhou; Dongshan Zhao; Hao Long; YuPing Liu; Xingzhong Zhao (pp. 7905-7911).

Carbon nanotubes (CNTs) have been grown directly on a Si substrate without a diffusion barrier in ethanol diffusion flame using Ni as the catalyst after a photoresist-assisted catalyst annealing process. The growth mechanism of as-synthesized CNTs is confirmed by scanning electron microscopy, high resolution transmission-electron microscopy and energy-dispersive spectroscopy. The photoresist is the key for the formation of active catalyst particles during annealing process, which then result in the growth of CNTs. The catalyst annealing temperature has been found to affect the morphologies and field electron emission properties of CNTs significantly. The field emission properties of as-grown CNTs are investigated with a diode structure and the obtained CNTs exhibit enhanced characteristics. This technique will be applicable to a low-cost fabrication process of electron-emitter arrays.

Keywords: PACS; 61.46.Fg; 81.16.Be; 79.60.Jv; 85.35.KtCarbon nanotubes; Flame synthesis; Field emission; Annealing; Photoresist

Self-assembly of human plasma fibrinogens on binary organosilane monolayers with micro domains by S.H. Lee; N. Saito; O. Takai (pp. 7912-7917).

The adsorption behavior and self-assembly of human plasma fibrinogen (HPF) on binary methyl- and amino-terminated self-assembled monolayers (SAMs) were investigated by atomic force microscopy (AFM). The binary SAMs were fabricated through self-assembly mechanism of organosilane molecules. The height of domains is the domain height is 0.8±0.2nm from the AFM topographic image. It corresponds to the domain height is 0.8±0.2nm from the AFM topographic image. It corresponds to the difference between the length of the alkyl chain of octadecyltrichlorosilane (OTS) and that of n-(6-aminohexyl)aminopropyltrimethoxysilane (AHAPS). The fibrinogen solution used ultrapure water as the solvent and its pH was adjusted at 3 and 10. From the AFM results at pH 3, HPF only formed network structures on the OTS domains of the binary SAM at early immersion times, and then the network structures expanded and connected between OTS domains through the AHAPS surface at long immersion times. In this case, a few HPFs are discretely adsorbed on the AHAPS surface. However, HPF is uniformly adsorbed on the binary SAM under the other conditions of pH.

Keywords: Human plasma fibrinogen; Organosilane self-assembled monolayer; Binary monolayer; Atomic force microscopy

Visible-light-activated Ce–Si co-doped TiO₂ photocatalyst by Qifeng Chen; Dong Jiang; Weimei Shi; Dong Wu; Yao Xu (pp. 7918-7924).

To enhance the visible photocatalytic activity and thermal stability of TiO₂, Ce–Si co-doped TiO₂ materials were synthesized through a nonaqueous method of which the purpose was to reduce the aggregation between TiO₂ particles. The obtained materials maintained anatase phase and large surface area of 103.3m²g⁻¹ even after calcined at 800°C. The XPS results also indicated that Si was weaved into the lattice of TiO₂, and Ce mainly existed as oxides on the surface of TiO₂ particles. The doped Si might enhance surface area and suppress transformation from anatase to rutile, while the doped Ce might cause visible absorption and inhibit crystallite growth during heat treatment. Evaluated by decomposing dye Rhodamine B, visible photocatalytic activity of Ce–Si co-doped TiO₂ was obviously higher than that of pure TiO₂ and reached the maximum at Ce and Si contents of 0.5mol% and 10mol%.

Keywords: Titanium dioxide; Ce–Si co-doping; Visible light; Photocatalysis

Surface analysis, TEM, dynamic and controlled rate thermal analysis, and infrared emission spectroscopy of gallium doped boehmite nanofibres and nanosheets by Jing Yang; Yanyan Zhao; Ray L. Frost (pp. 7925-7936).

Ga doped boehmite nanofibres with varying Ga content have been prepared at low temperatures using hydrothermal treatment in the presence of poly (ethylene oxide) surfactant. The resulting nanofibres were characterized by X-ray diffraction (XRD), dynamic and controlled rate thermal analysis and infrared emission spectroscopy (IES), transmission electron microscopy (TEM), Energy dispersive X-ray analysis (EDX), N₂ adsorption/desorption. TEM results show that nanotubes are dominant when the doped gallium percentage is no more than 5%; nanosheets and an amorphous phase are observed in 10% and 20% gallium doped samples. N₂ adsorption/desorption analysis reveals a large amount of micropores and mesopores are present in the resultant samples. Similar to iron and yttrium doped boehmite nanomaterials, remarkable larger BET specific area was achieved compared to pure boehmite nanomaterials. Both dynamic and controlled thermal analyses show that the gallium doped boehmite nanomaterials dehydrate at higher temperature than that of pure boehmite. Interestingly, the higher the crystallinity of the resultant nanotubes is, the higher the dehydration temperature. The IES spectra show that dehydroxylation of the resultant gallium doped boehmite nanomaterials starts at 250°C and is complete by 450°C, in harmony with the dynamic and controlled rate thermal analysis results.

Keywords: Doped boehmite; Acicular; Nanofibre; Nanotube; Nanosheets

Covalent immobilization of glucose oxidase onto Poly(St-GMA-NaSS) monodisperse microspheres via BSA as spacer arm by Tanxin Du; Bailing Liu; Xiaohui Hou; Baotan Zhang; Cuiming Du (pp. 7937-7941).

In this study, the immobilization of glucose oxidase (GOD) onto micron-size monodisperse Poly(Styrene-Glycidyl Methacrylate-Sodium Sulfonate Styrene) microspheres was investigated. In order to improve their surface biocompatibility, bovine serum albumin (BSA) was introduced onto the microspheres’ surface as a new type of spacer arm. Both the immobilization amount and enzymatic activity were determined in different experimental conditions (enzyme concentration, pH, temperature, etc.). It was found that BSA could serve as a good spacer because it increases both the immobilization amount and enzymatic activity of GOD. The tolerance of immobilized GOD against pH, temperatures was examined. Moreover, the kinetic parameters for native and immobilized GOD were obtained and compared.

Keywords: Covalent immobilization; BSA-spacer; Conformational change; Monodisperse microspheres

Influence of post-annealing on the properties of Sc-doped ZnO transparent conductive films deposited by radio-frequency sputtering by Xueqiang Liu; Weihong Bi; Zhaolun Liu (pp. 7942-7945).

Sc-doped ZnO transparent conductive films are deposited on glass substrates by radio-frequency sputtering. The influence of post-annealing on the structural, morphologic, electrical, and optical properties of the films is investigated by energy dispersion X-ray spectroscopy, X-ray diffraction, Hall measurement, and optical transmission spectroscopy. The experimental results show that these films are polycrystalline with a preferred [001] orientation. The lowest resistivity of 2.6×10⁻⁴Ωcm is obtained from the film annealed at 500°C. The average optical transmittance of the films is over 90%. These results suggest that Sc-doped ZnO is a good candidate for fabricating high performance transparent conductive films.

Keywords: PACS; 42.25.Fx; 42.70.Km; 78. 20.−eSemiconductors; Electrical properties; Thin films; Transparent conductive films; Radio-frequency sputtering

Linear dichroism, produced by thermo-electric alignment of silver nanoparticles on the surface of ion-exchanged glass by Arashmid Nahal; Kiyanoosh Shapoori (pp. 7946-7950).

A heated Ag⁺-doped glass is subjected to an external constant uniform electric field ( E_o>250V/cm) parallel to its surface. Absorption spectra studies by linear polarized light imply the induction of a linear dichroism in the samples, after the above-mentioned thermo-electrical process. It is found that the increase in the temperature (400°C≤ T≤600°C), results in the formation of neutral silver multimers and clusters on the samples. Dichroism is the result of simultaneous application of the steady uniform electric field and heating. That is, the process aligns the produced silver nanoparticles along the applied electric field ( E_o) during the aggregation of silver nano-clusters via dipole–dipole interaction, leading to the formation of chain-like conductive structures.

Keywords: Silver nanoparticles; Ion-exchanged glass; Dichroism

Surface behavior during abrasive grain action in the glass lapping process by Nabil Belkhir; Djamel Bouzid; Volker Herold (pp. 7951-7958).

In this study the surface behavior during its contact with the abrasive grain in the glass lapping process was studied using practical simulation which is the scratch test and the real contact between glass surfaces and α-alumina abrasive grains during lapping process. Formations and dimensions of the produced scratches were investigated to explain the grain action on the surface and the glass material removal rate. It has been found that humid environment created by the use of the slurry of loose abrasives causes more significant damages than the dry one. The use of slurry produces higher glass material removal rate in this environment and proves its utility in the lapping process. The shape of abrasive grains influences the nature of their action. Indeed, the worn grains produce scratches and chippings less than the sharp grains. During lapping, the number of scratches and theirs dimensions depend on the contact time and the abrasive grain size. It was concluded that the glass material removal rate during lapping depends on the cumulative actions of individual grains which produce scratches and chippings.

Keywords: Material removal; Lapping; Glass surface; Scratch; Subsurface damage

Improvement in tribological properties of atmospheric plasma-sprayed WC–Co coating followed by Cu electrochemical impregnation by Jianhui Yuan; Yingchun Zhu; Xuebing Zheng; Qichao Ruan; Heng Ji (pp. 7959-7965).

The WC–Co coating obtained by atmospheric plasma spraying (APS) was modified by Cu electrochemical impregnation. The copper has infiltrated into and filled up the pores in WC–Co coating. The tribological properties of the coating against the stainless steel ball as sliding pairs were investigated with a ball-on-disc (BOD) configuration in air at room temperature. The as-prepared samples were characterized by means of optical microscope, scanning electron microscope and X-ray diffraction. It was found that the frictional behavior of the WC–Co coating followed by Cu electrochemical impregnation was superior to that of WC–Co coating. The wear mechanism of the WC–Co coating followed by Cu electrochemical impregnation was microcutting, whilst that of a WC–Co coating was the fatigue wear. The improvement in tribological properties of the WC–Co coating followed by Cu electrochemical impregnation was attributed to the formation of self-lubricating Cu film on the wear surface which induces the transformation of wear mechanism.

Keywords: Tribological property; WC–Co coating; Plasma spraying; Electrochemical impregnation

XPS and SRUPS study of oxygen adsorption on Cd_0.9Zn_0.1Te (111)A surface by Xuxu Bai; Wanqi Jie; Gangqiang Zha; Wenhua Zhang; Peisen Li; Hui Hua; Li Fu (pp. 7966-7969).

Synchrotron radiation ultraviolet photoemission spectroscopy (SRUPS) and X-ray photoelectron spectroscopy (XPS) have been applied to investigate oxygen adsorption on a cadmium zinc telluride (CZT) (111)A surface. The surface chemical composition and the surface oxidation process were monitored by recording the Te 3d, O 1s, Zn 2p, Cd 4d core level peaks, and the Cd MNN Auger peak. The CZT (111)A surface was effectively oxidized by dosing oxygen directly. The typical surface state of the clean CZT (111)A surface was identified. After oxygen exposure, this surface state disappeared and a signal due to the formation of O–CZT appeared. In addition, the work function of CZT decreased with the increasing oxygen exposure.

Keywords: CZT; Oxygen adsorption; Work function; SRUPS; XPS

Improving the stability of organic light-emitting devices using a solution-processed hole-injecting layer by Xinwen Zhang; Zhaoxin Wu; Dongdong Wang; Dawei Wang; Xun Hou (pp. 7970-7973).

The stability of organic light-emitting devices with a spin-coated film of 4,4′,4″-tris(3-methylphenylphenylamino)triphenylamine (m-MTDATA) as hole-injection layer (HIL) was investigated. The lifetime of this device is increased to 40900h (with an initial luminance of 100cd/m²), which is 2.7 times as large as that of the control device with a vacuum-deposited film of m-MTDATA as HIL. A significant feature with this method is that the performance and the operational stability of the device with spin-coated HIL are little attenuated by the rough substrate coated by the indium-tin oxide film. The surface morphology of the solution-processed m-MTDATA thin film is quite even and uniform, and it acts as a smoothing layer in the device, which leads to the stability enhancement of the device.

Keywords: Organic light-emitting devices; Solution-processed; Stability

Fabrication of cyclodextrin-functionalized superparamagnetic Fe₃O₄/amino-silane core–shell nanoparticles via layer-by-layer method by Haining Cao; Jiang He; Li Deng; Xiaoqing Gao (pp. 7974-7980).

This paper presents a feasible protocol for the preparation of a novel versatile nanocomposite possessing superparamagnetism via a layer-by-layer method. We combined (3-aminopropyl)triethoxysilane-coated magnetic Fe₃O₄ nanoparticles (APTES-MNPs) with β-cyclodextrin (β-CD). The following unusual features were integrated in a single nano-system: (a) the silane coating outside the magnetic Fe₃O₄ cores derived from the hydrolysis of APTES acted as a coupling agent and provided amino group (–NH₂) for linking the CD molecule; (b) the outermost CD moieties can function as inclusion sites and specific containers for drugs and biomolecules; (c) the innermost magnetic cores were able to sense and respond to an externally applied magnetic field and their behaviors in vivo or in vitro can be artificially manipulated and navigated. The obtained nanocomposite turned out to be superparamagnetic with a relatively high saturation magnetization value of 69emug⁻¹, which implies potentially promising applications in magnetic drug delivery technology and bioseparation.

Keywords: Magnetite nanoparticle; APTES coating; Amino-silane; Cyclodextrin modification; Superparamagnetic

Structure, optical, and magnetic properties of rutile Sn1−_xMn_xO₂ thin films by Yuhua Xiao; Shihui Ge; Li Xi; Yalu Zuo; Xueyun Zhou; Li Zhang; Guowei Wang; Xiufeng Han; Zhenchao Wen (pp. 7981-7984).

Sn1−_xMn_xO₂ ( x≤0.11) thin films were fabricated by sol–gel and spin-coated method on Si (111) substrate. 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. Optical transmission studies show that the band gap energy ( E_g) broadens with the increasing of Mn content. Magnetic measurements revealed that all samples exhibit room temperature ferromagnetism (RTFM), which is identified as an intrinsic characteristic. Interestingly, the magnetic moment per Mn atom decreases with the increasing Mn content. The origin of RTFM can be interpreted in terms of the bound magnetic polaron model.

Keywords: Room temperature ferromagnetism; Mn-doped SnO; ₂; film; Bound magnetic polaron

Flame synthesis of carbon nanotubes for panel field emission lamp by Y.X. Liu; J.H. Liu; C.C. Zhu (pp. 7985-7989).

Multi-walled carbon nanotubes (CNTs) were synthesized on the surfaces of Ni-alloy plated Fe-wires with the diameter of 2mm using a conventional laboratory ethanol (C₂H₅OH) flame method at 560°C. SEM showed that the product had bush-shaped micron-structures with diameters from 100 to 450nm and lengths of over 1.0μm. TEM revealed that the micron-structures were composed of multi-walled nanotube bundles with the diameters of about 50nm. The test on the diode configuration field emission of the Fe-wire arrays was performed. The onset electric field was 2.95V/μm and the emission current can reach 50mA/cm² at an electric field of 9V/μm. The average fluctuation of the emission current density was less than 7%. The result suggests that the field emission was uniform and the present technique was feasible to fabricate Panel Field Emission Lamp (PFEL) with arrays of carbon nanotubes. PFEL has the advantages of high luminescence as well as stability, and thus, it can be used to replace ordinary lights.

Keywords: Carbon nanotubes; Flame synthesis; Field emission lamps; Simple fabrication method

Preparation and colloidal behaviour of surface-modified EuF₃ by Anatoly Safronikhin; Tatyana Shcherba; Heinrich Ehrlich; Georgy Lisichkin (pp. 7990-7994).

Surface-modified EuF₃ nanoparticles has been produced by mixing of NaF and Eu(NO₃)₃ aqueous solutions in the presence of sodium citrate as stabilizer. Transmission electron microscopy and dynamic light scattering has shown citric ions influence on the particle size and morphology. Modified and unmodified EuF₃ samples were characterized by X-ray diffraction, elemental analysis, IR and luminescence spectroscopy. The results indicate that citrate ions bond chemically with EuF₃ particle, forming a layer onto the surface. The layer stabilizes nanoparticle colloids and prevents their aggregation. In the case of modified EuF₃ colloids, reversible precipitation–peptization processes at varying pH values and Cu²⁺ chemosorption by citric layer are revealed.

Keywords: Surface modification; Europium fluoride; Citric acid; Nanoparticles

Optical properties of PMN–PT thin films prepared using pulsed laser deposition by X.L. Tong; K. Lin; D.J. Lv; M.H. Yang; Z.X. Liu; D.S. Zhang (pp. 7995-7998).

(1− x)Pb(Mg_1/3Nb_2/3)O₃– xPbTiO₃ (PMN–PT) thin films have been deposited on quartz substrates using pulsed laser deposition (PLD). Crystalline microstructure of the deposited PMN–PT thin films has been investigated with X-ray diffraction (XRD). Optical transmission spectroscopy and Raman spectroscopy are used to characterize optical properties of the deposited PMN–PT thin films. The results show that the PMN–PT thin films of perovskite structure have been formed, and the crystalline and optical properties of the PMN–PT thin films can be improved as increasing the annealing temperature to 750°C, but further increasing the annealing temperature to 950°C may lead to a degradation of the crystallinity and the optical properties of the PMN–PT thin films. In addition, a weak second harmonic intensity (SHG) has been observed for the PMN–PT thin film formed at the optimum annealing temperature of 750°C according to Maker fringe method. All these suggest that the annealing temperature has significant effect on the structural and optical properties of the PMN–PT thin films.

Keywords: PACS; 77.84.Dy; 68.55.−a; 77.22.−dPMN–PT thin films; Laser deposition; Structural and optical property

Electrostatic self-assembly of Fe₃O₄ nanoparticles on carbon nanotubes by Yong Liu; Wei Jiang; Song Li; Fengsheng Li (pp. 7999-8002).

Carbon nanotubes (CNTs)-based magnetic nanocomposites can find numerous applications in nanotechnology, integrated functional system, and in medicine owing to their great potentialities. Herein, densely distributed magnetic Fe₃O₄ nanoparticles were successfully attached onto the convex surfaces of carbon nanotubes (CNTs) by an in situ polyol-medium solvothermal method via non-covalent functionalization of CNTs with cationic surfactant, cetyltrimethylammonium bromide (CTAB), and anionic polyelectrolyte, poly(sodium 4-styrenesulfonate) (PSS), through the polymer-wrapping technique, in which the negatively charged PSS-grafted CNTs can be used as primer for efficiently adsorption of positively metal ions on the basis of electrostatic attraction. X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analysis have been used to study the formation of Fe₃O₄/CNTs. The Fe₃O₄/CNTs nanocomposites were proved to be superparamagnetic with saturation magnetization of 43.5emug⁻¹. A mechanism scheme was proposed to illustrate the formation process of the magnetic nanocomposites.

Keywords: Self-assembling; Magnetite; Carbon nanotubes; Nanocomposites; Solvothermal method

Effects of growth temperature modulated by HCl flow rate on the surface and crystal qualities of thick GaN by HVPE by Lubing Zhao; Jiejun Wu; Ke Xu; Zhijian Yang; Guoyi Zhang (pp. 8003-8009).

We studied the influence of the growth temperature and HCl flow rate on the morphological evolution of crack-free thick GaN films by using a home-made horizontal hydride vapor phase epitaxy on sapphire substrates. Optical difference microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and cathodoluminescence (CL) were carried out to reveal the surface property of the GaN epilayer. It was found that the higher growth temperature is a key factor to obtain mirror, colorless and flat GaN surface. However, this key effect of temperature was modulated by HCl flow rate (HCl>15sccm). The surface RMS roughness was reduced from 206 to 2.51nm for 10μm×10μm scan area when GaN was grown at 1070°C with HCl flow rate up to 30sccm. These samples also reduced their (0002) FWHM result from 1000 to 300arcsec and showed a strong near-band-edge peak in CL spectra. Results indicated that growth temperature influence growth velocities on different crystalline planes, which will lead to the different morphologies obtained. High growth temperature can improve the lateral growth rate of vertical {11−20} facets and reduce the vertical growth rate of top {0001} facet combined with higher HCl flow rate, which leads to completely coalescence of surface.

Keywords: PACS; 68.55.−a; 78.55.Cr; 81.15.GhThick GaN; Growth temperature; HCl flow rate; Hydride vapor phase epitaxy; Surface and crystal qualities

Self-consistent theory for the built-in voltage in metal–organic semiconductor–metal structures by Ying-quan Peng; Wei-min Meng; Run-sheng Wang; Chao-zhu Ma; Xun-shuan Li; Hong-wei Xie; Rong-hua Li; Ming Zhao; Jian-ting Yuan; Ying Wang (pp. 8010-8013).

A self-consistent theory for calculation of built-in voltage ( U_bi) of metal–organic semiconductor–metal (MOSM) structures is developed based on Gaussian energy distribution of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). It is shown that the built-in voltage depends not only on the work function difference of the two electrodes, but also on the mean energy level of HOMO and LUMO, as well as the Gaussian width of the energy distribution. The theory predicts that the spreading of HOMO and LUMO levels will results in an increase of U_bi, and that U_bi decreases with increasing temperature.

Keywords: Built-in voltage; Metal–organic semiconductor–metal structure; Theory

Swift heavy ion induced modifications in cobalt doped ZnO thin films: Structural and optical studies by Sunil Kumar; R. Kumar; D.P. Singh (pp. 8014-8018).

Modifications in the structural and optical properties of 100MeV Ni⁷⁺ ions irradiated cobalt doped ZnO thin films (Zn1−_xCo_xO, x=0.05) prepared by sol–gel route were studied. The films irradiated with a fluence of 1×10¹³ions/cm² were single phase and show improved crystalline structure with preferred C-axis orientation as revealed from XRD analysis. Effects of irradiation on bond structure of thin films were studied by FTIR spectroscopy. The spectrum shows no change in bonding structure of Zn–O after irradiation. Improved quality of films is further supported by FTIR studies. Optical properties of the pristine and irradiated samples have been determined by using UV–vis spectroscopic technique. Optical absorption spectra show an appreciable red shift in the band gap of irradiated Zn1−_xCo_xO thin film due to sp–d interaction between Co²⁺ ions and ZnO band electrons. Transmission spectra show absorption band edges at 1.8eV, 2.05eV and 2.18eV corresponding to d–d transition of Co²⁺ ions in tetrahedral field of ZnO. The AFM study shows a slight increase in grain size and surface roughness of the thin films after irradiation.

Keywords: Swift heavy ions (SHI); Cobalt doped ZnO thin films; X-ray diffraction; FTIR; UV–vis spectroscopy

Replication of mold for UV-nanoimprint lithography using AAO membrane by Weimin Zhou; Jing Zhang; Xiaoli Li; Yanbo Liu; Guoquan Min; Zhitang Song; Jianping Zhang (pp. 8019-8022).

A simple and highly effective method to the replication of soft mold based on the anodic aluminum oxide (AAO) membrane was developed. The soft mold with nanopillar arrays was composed of the toluene diluted PDMS layer supported by the soft PDMS. A water contact angle as high as 114° was achieved. The hexagonally well-order arrays of holes of nanometer dimensions, ∼100nm pore diameter and 125nm center-to-center pore, could be gained over large areas by UV-nanoimprint lithography (UV-NIL) with the replicated soft PDMS mold. It is expected that the developed soft mold would find applications in light emitting diodes devices.

Keywords: PACS; 81.16.Rf; 81.65.Mq; 81.16.Dn; 85.40.HpAAO membrane; Soft lithography; UV-nanoimprint lithography

Optical properties of hybrid polymers as barrier materials by D. Georgiou; A. Laskarakis; S. Logothetidis; S. Amberg-Scwhab; U. Weber; M. Schmidt; K. Noller (pp. 8023-8029).

The development of high barrier films for the encapsulation of organic electronics devices onto flexible polymeric substrates is attracting a considerable scientific interest, since it is important to protect the organic semiconductor layers of these devices from corrosion due to atmospheric gas molecule permeation. The barrier layers for encapsulation consist of a sequence of inorganic and hybrid polymer thin films that are deposited onto flexible polymeric substrates, such as polyethylene terephthalate (PET). In addition to their barrier response, these multilayer systems should also exhibit high transparency and good adhesion between the hybrid polymer and inorganic layers. The knowledge of their optical properties and the correlation of the optical response with their structure and the final barrier response are of major importance since it will contribute towards the optimization of their functionality. In this work, the optical properties of hybrid polymers deposited onto silicon oxide inorganic thin films that were grown onto flexible polymeric substrates, have been investigated by the use of spectroscopic ellipsometry in a wide spectral region from the infrared to the visible–ultra violet. As it has been found, the increase of the solid content in the hybrid polymers is associated with a reduction in the refractive index values. This behavior can be correlated to a lower density of the hybrid polymer, and furthermore to a poor barrier response, due to the less cohesive inorganic–organic bonding network. Finally, from the investigation of the optical response of the hybrid polymers in the IR spectral region has revealed information on their bonding structure that has been discussed together with their barrier response.

Keywords: Hybrid polymers; Barrier; Spectroscopic ellipsometry; Encapsulation; Flexible organic electronics

Surface modification and submicron structure of carbon fibers through high current pulse by Limin Li; Lie Liu; Hong Wan; Qifu Xu; Guoxin Cheng; Jianchun Wen (pp. 8030-8035).

This paper investigated the behavior of carbon fibers subjected to a ∼20kA, ∼5μs high current pulse. It was found that the broken fibers and submicron particles were generated by electrical explosion process. After high current pulsed discharge, the fiber diameter increased significantly, from 5–7μm to ∼13μm. Also, the surface rupture of carbon fibers with valleys of hundreds of nanometers was observed. Most notably, the submicron particles appeared with two typical shapes (near-sphere and square). The high current pulsed discharge of carbon fibers can be divided into three stages, namely, heating stage, phase change stage, and explosion stage. Indeed, the electrical explosion process occurred in the last stage of ∼200ns. The nature behind these results is closely related to the plasma development during the explosion process. The plasma expansion due to a large plasma thermal stress leads to the incomplete explosion. In the explosion stage, the current passing through the fibers exhibited a huge fluctuation, indicating plasma instabilities. Finally, the physical mechanisms, how to affect the surface morphology of carbon fibers, are presented.

Keywords: Carbon fiber; Electrical explosion; Surface modification; Submicron particles

Photodegradation of dye pollutants catalyzed by γ-Bi₂MoO₆ nanoplate under visible light irradiation by Xu Zhao; Tongguang Xu; Wenqing Yao; Yongfa Zhu (pp. 8036-8040).

Nanoplate γ-Bi₂MoO₆ is prepared by hydrothermal method. Using this material as photocatalyst, rhodamine B and methylene blue were efficiently degraded under visible light irradiation. The degradation kinetics, total organic carbon changes, and electron spin resonance detection of active oxygen species were investigated to clarify the degradation process. The experimental results indicated that the target dyes could be facilely bleached and mineralized. The formation of active oxygen species ofOH and O²⁻ is detected, and they are proposed to be responsible for the degradation of the target dyes. The γ-Bi₂MoO₆ catalyst is very stable and can be reused.

Keywords: Bismuth molybdates; Photocatalysis; Visible light; Rhodamine B; Methylene blue

Characteristics of sculptured Cu thin films and their optical properties as a function of deposition rate by H. Savaloni; F. Babaei; S. Song; F. Placido (pp. 8041-8047).

Sculptured copper thin films were deposited on glass substrates, using different deposition rates. The nano-structure and morphology of the films were obtained, using X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Their optical properties were measured by spectrophotometry in the spectral range of 340–850nm. The real and imaginary refractive indices, film thickness and fraction of metal inclusion in the film structure were obtained from optical fitting of the spectrophotometer data.

Keywords: PACS; 61.05.−a; 68.37.−d; 81.15.−z; 78.20.ci; 78.68.+mSculptured thin films; Bruggeman effective medium approximation; AFM; XRD; SEM

Effect of natural and magnetic convections on the structure of electrodeposited zinc–nickel alloy by A. Levesque; S. Chouchane; J. Douglade; R. Rehamnia; J.-P. Chopart (pp. 8048-8053).

The effects of a magnetic field applied in a direction parallel or perpendicular to the cathode substrate plane, during electrodeposition process of Zn–Ni alloy have been investigated by means of chronoamperometric measurements, X-ray diffraction and EDX analysis. The modification of crystal orientation of the alloy by the superimposition of a high magnetic field is discussed for alloys with a content of nickel range 6–13at%. Whatever the phase composition obtained without magnetic field, either γ-Ni₅Zn₂₁ or a mixture of the γ and zinc phases, which depends on the concentration of Ni²⁺ in the electrolyte bath, the preferential orientation (101) of the zinc phase is always favoured with perpendicular and parallel magnetic field. There is no saturation of this effect with amplitude of B up to 8T. A study of different geometric configurations of the cathode, which induce more or less natural convection, consolidates these results. The structural modifications of Zn–Ni alloy electrodeposits are thus probably due to a magnetohydrodynamic effect. An additional phenomenon is observed in presence of a perpendicular applied magnetic field since the (330) preferential orientation of the γ-Ni₅Zn₂₁ disappears with high values of B.

Keywords: Zn–Ni alloy; Magnetic field; Electrodeposition; XRD; Magnetoelectrochemistry; Magnetohydrodynamics

Influence of the OH groups on the photocatalytic activity and photoinduced hydrophilicity of microwave assisted sol–gel TiO₂ film by Morten E. Simonsen; Zheshen Li; Erik G. Søgaard (pp. 8054-8062).

In the present work the influence of the OH groups on the photocatalytic activity and the photoinduced hydrophilicity of microwave assisted sol–gel TiO₂ films was investigated. The prepared TiO₂ films were characterized using XRD and AFM. Furthermore, the surface of the TiO₂ films was examined by help of XPS in order to determine the amount of OH groups before and after UV irradiation at different humidities. The activity of the TiO₂ films was determined using stearic acid as a model compound and the photoinduced superhydrophilicity was investigated through contact angle measurements.The results of this investigation showed that the microwave assisted sol–gel technique produces highly homogeneous and efficient TiO₂ films without the need for heat treatment for crystallization. Based on the conducted experiments it is suggested that the amount of OH groups on the TiO₂ surface highly influence the photocatalytic activity and the photoinduced superhydrophilicity and that the two mechanisms may be closely related. It is suggested that the superhydrophilicity is obtained through a combination of photocatalytic degradation of organic contaminants and surface structural changes in form of an increased amount of OH-groups.

Keywords: OH-groups; XPS; Superhydrophilicity; Sol–gel film; Humidity; TiO; ₂

Preparation and photocatalytic properties of silver nanoparticles loaded on CNTs/TiO₂ composite by Shuo Wang; Qianming Gong; Yuefeng Zhu; Ji Liang (pp. 8063-8066).

In this study, new nanoscale photocatalyst based on silver and CNTs/TiO₂ was successfully prepared by photoreduction method. The prepared Ag-CNTs/TiO₂ was characterized by TEM, XRD and XPS. The photocatalytic activity was also evaluated by photocatalytic degradation of Reactive Brilliant Red X-3B dye. The results indicated that the photocatalytic efficiency of CNTs/TiO₂ increased in the presence of Ag nanoparticles and the photocatalysis reaction followed a first order kinetics. The kinetic constant of Ag-CNTs/TiO₂ for dye degradation was nearly 1.2 times than that of CNTs/TiO₂, which indicated decorating Ag nanoparticles on CNTs/TiO₂ could enhance the photocatalytic ability.

Keywords: Carbon nanotubes; Titanium oxide; Silver; Photocatalysis

Synthesis, characterization and cytotoxicity of surface amino-functionalized water-dispersible multi-walled carbon nanotubes by Goran Vuković; Aleksandar Marinković; Maja Obradović; Velimir Radmilović; Miodrag Čolić; Radoslav Aleksić; Petar S. Uskoković (pp. 8067-8075).

Surface functionalization of multi-walled carbon nanotubes (MWCNTs), with amino groups via chemical modification of carboxyl groups introduced on the nanotube surface, using O-(7-azabenzotriazol-1-yl)- N, N, N′, N′-tetramethyluronium hexafluorophosphate (N-HATU) and N, N-diisopropylethylamine (DIEA) is reported. The N-HATU coupling agent provides faster reaction rate and the reaction occurs at lower temperature compared to amidation and acylation–amidation chemistry. The amines, 1,6-hexanediamine (HDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and 1,4-phenylenediamine (PDA) were used. The resulting materials were characterized with different techniques such as FTIR, XRD, elemental analysis, TGA, TEM, UV–vis spectroscopy and cyclic voltammetry. MWCNTs functionalized with PDA posses the best dispersibility and electron transfer properties in comparison to the others amines. Functionalized MWCNTs, at the concentrations between 1 and 50μgml⁻¹, were not cytotoxic for the fibroblast L929 cell line. However, the concentrations of MWCNTs higher of 10μgml⁻¹ reduced cell growth and this effect correlated positively with the degree of their uptake by L929 cells.

Keywords: Carbon nanotubes; Amino-functionalization; Cyclic voltammetry; Cytotoxicity

Characterization of nanocrystalline gold/DLC composite films synthesized by plasma CVD technique by R. Paul; S. Hussain; A.K. Pal (pp. 8076-8083).

Composite films containing gold nanoparticles embedded in diamond-like carbon (Au–DLC) matrix were deposited on glass and Si (100) substrates by using capacitatively coupled plasma (CCP) chemical vapour deposition technique (CVD). Particle size and metal volume fraction were tailored by varying the relative amount of argon in the methane+argon gas mixture in the plasma. Optical constants of the films were evaluated. Bonding environment in these films were obtained from Raman and Fourier transformed infrared spectra (FTIR) studies. Blue-shift of the surface plasmon resonance peak in the optical absorbance spectra of the films could be associated with the reduction of the particle size while red shift was observed with the increase in volume fraction of metal particles in the DLC films. Absorption spectra recorded in the reflection mode indicated dichromatism in these films.

Keywords: PACS; 78.67.−nSurface plasmon; Diamond-like carbon; Nanocrystalline gold

Electrochemical and surface characterisation of carbon-film-coated piezoelectric quartz crystals by Edilson M. Pinto; Carla Gouveia-Caridade; David M. Soares; Christopher M.A. Brett (pp. 8084-8090).

The electrochemical properties of carbon films, of thickness between 200 and 500nm, sputter-coated on gold- and platinum-coated 6MHz piezoelectric quartz crystal oscillators, as new electrode materials have been investigated. Comparative studies under the same experimental conditions were performed on bulk electrodes. Cyclic voltammetry was carried out in 0.1M KCl electrolyte solution, and kinetic parameters of the model redox systems Fe(CN)₆^3−/4− and [Ru(NH₃)₆]^3+/2+ as well as the electroactive area of the electrodes were obtained. Atomic force microscopy was used in order to examine the surface morphology of the films, and the properties of the carbon films and the electrode-solution interface were studied by electrochemical impedance spectroscopy. The results obtained demonstrate the feasibility of the preparation and development of nanometer thick carbon film modified quartz crystals. Such modified crystals should open up new opportunities for the investigation of electrode processes at carbon electrodes and for the application of electrochemical sensing associated with the EQCM.

Keywords: Piezoelectric crystals; Electrochemical quartz crystal microbalance; Carbon; Electrochemistry; Atomic force microscopy

Morphology controlled solvothermal synthesis of Cd(OH)₂ and CdO micro/nanocrystals on Cd foil by Tandra Ghoshal; Soumitra Kar; S.K. De (pp. 8091-8097).

Cadmium hydroxide (Cd(OH)₂) and cadmium oxide (CdO) nano and micro crystals were synthesized in ethanol–water medium using cadmium foil both as a source and substrate under solvothermal condition. Different concentrations of ammonium hydroxide, hydrazine hydrate, sodium hydroxide and potassium hydroxide were added to study the structural and morphological variations in the products. Synthesis was carried out at different temperatures to study the growth stages of the nano/microstructures. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The as-prepared Cd(OH)₂ products were transformed to CdO by thermal treatment in air. The possible growth mechanism for the formation of different morphologies at different basic medium has been proposed. The optical absorption measurement was carried out to determine the values of the band gap of CdO.

Keywords: PACS; 81.10.Dn; 68.37.Hk; 61.82.RxScanning and transmission electron microscopy; Optical absorption spectroscopy; Solvothermal process; Nanowires; Nanoribbons; Cadmium oxide

Surface modification and characterization of Jordanian kaolinite: Application for lead removal from aqueous solutions by Mohammad Al-Harahsheh; Reyad Shawabkeh; Adnan Al-Harahsheh; Khalid Tarawneh; Marwan M. Batiha (pp. 8098-8103).

Kaolinite clay was tested for removal of lead ions from aqueous solution. This clay was washed with sulfuric acid solution followed by chemical surface modification using 3-chloropropyltriethoxysilane and sodium hydroxide. XRF results showed that silica to alumina ratio was 2.8:1 for the treated sample compared to 1.6:1 for the raw one.XRD analysis displayed different distinct kaolinite and quartz peaks before treatment while kaolinite peaks were diminished after the treatment. SEM morphology indicated that the raw kaolinite appears as plate structure with no local pores on the plates. However, after treatment the surface was found to have micropores.Different adsorption isotherm models were applied to the experimental data and found that Shawabkeh–Tutunji equation best fit these data adequately. It was also found that chemisorption took place at the surface of the modified kaolinite with maximum adsorption capacity of 54.35mg/g.

Keywords: Lead removal; Kaolinite; Adsorption; Surface modification

Structural and electrical transport properties of Nb-doped TiO₂ films deposited on LaAlO₃ by rf sputtering by Xiao Wan Zheng; Zhi Qing Li (pp. 8104-8109).

We have investigated the structural and electrical transport properties of Nb-doped TiO₂ films deposited on (100) LaAlO₃ substrates by rf magnetron sputtering at temperatures ranging from 873K to 1073K. Films deposited below 998K are anatase, and mixed phases between anatase and rutile exist in the film grown at higher temperatures. We find that films deposited at low temperatures exhibit semiconductor behavior, while metallic conductivity is observed in the most conducting film deposited at 998K. For this sample, compared to electron–phonon scattering mechanism, electron–phonon-impurity interference effect plays an important role in its electron transport process. Moreover, the temperature coefficient of the resistivity for the film deposited at 1073K is negative from 2K to 300K. The temperature dependence of resistivity for the film is described by ∼exp( b/ T)^1/2 at temperatures from 80K down to 30K, and by the fluctuation induced tunneling model from 80K to 300K.

Keywords: PACS; 73.61.Le; 81.05.Hd; 68.55.; ag; 81.15.CdElectrical transport; Transparent conducting oxide; rf sputtering

Improved determination of phosphorus contamination during ion implantation by SRP and simulations by M. Kuruc; L. Hulényi; R. Kinder (pp. 8110-8114).

Experimental determination of phosphorous cross-contamination during antimony implantation is presented. As a suitable structure for this experiment, a buried layer was employed which is created by implanting antimony followed by a long diffusion process. The implanted samples were analysed by SIMS and spreading resistance (SRP) methods. SRP method has been improved by applying a correction for the carrier spilling effect. A conversion chart for p– n junction depth dependence on phosphorus doping has been calculated by program SUPREM-IV. Comparison of SRP and SIMS methods has shown that SRP method can be used for monitoring the phosphorus cross-contamination and can be easily implemented as an in-line monitor and present an alternative to expensive and time consuming SIMS analysis.

Keywords: PACS; 81.05.Ea; 84.37.+q; 85.40.RyPhosphorus; Antimony; Implantation; Cross-contamination; Doping profile; SIMS; Spreading resistance; Simulation

Surface analysis of long-distance oxygen plasma sterilized PTFE film by Hongxia Liu; Huijun Zhang; Jierong Chen (pp. 8115-8121).

The influence of long-distance oxygen plasma sterilization on surface properties of substrate material, i.e., medical poly(tetrafluoroethylene) (PTFE), and aging effect of these sterilized PTFE film surfaces were investigated by contact angle measurement, mass loss determination, scanning electron microscopy (SEM) as well as bacterial adhesion and platelet adhesion measurements in vitro, respectively. The changes in chemical structure of sterilized PTFE film were followed using X-ray photoelectron spectroscopy (XPS). As a result of plasma sterilization oxygen-containing functional groups (such as CO and CO), especially the CO group are introduced into PTFE surfaces, and thus pronounced increases of surface free energy and surface wettability are presented when the sample positions are within 0–40cm. The film surface wettability degrades little as the aging time continued as long as 190 days. At the same time, the minimal surface degradation and damage occur on the sterilized PTFE when the sample position is at 40cm. Moreover, the antibacterial adhesion and blood compatibility of sterilized PTFE surface are enhanced and the optimal effects are also obtained at 40cm. The essential reason may be due to the optimal equilibrium between surface wettability and surface damage, which is achieved at 40cm. Overall, of the surface properties of long-distance oxygen plasma sterilized PTFE analyzed, the sterilization at 40cm is optimal.

Keywords: PACS; 52.40.HfLong-distance oxygen plasma; Sterilization; PTFE; Surface property

Monte Carlo simulation of hydrogen physisorption in K-doped single walled carbon nanotube array by Xinghong Yuan; Jinrong Cheng; Xing Fang; Zhi Wang; Xiao Wang (pp. 8122-8125).

Properties of hydrogen physisorption in K-doped single walled carbon nanotube array (SWCNTA) are investigated in detail by grand canonical Monte Carlo simulation. The optimization of hydrogen storage capacity at 293K and 10MPa as a function of K-doping schemes, K atoms’ doped-sites, and SWCNTA configuration is discussed.

Keywords: PACS; 68.43.−h; 84.60.−h; 61.72.WwK-doping; Single walled carbon nanotube array; Physisorption; Hydrogen storage

Cladding of titanium/fluorapatite composites onto Ti6Al4V substrate and the in vitro behaviour in the simulated body fluid by Hezhou Ye; Xing Yang Liu; Han Ping Hong (pp. 8126-8134).

To improve the bioactivity of Ti6Al4V alloy, an innovative cladding method has been developed to bond a Ti/fluorapatite (FA) composite onto the alloy for load-bearing applications. With the aid of a silver interlayer and external pressure during sintering, a defect-free interface between the composite and the substrate was obtained. The fabricated materials were bioactive and could induce the nucleation and formation of bone-like carbonated apatite after immersed in the simulated body fluid (SBF). Functional ions, such as Ag⁺ and F⁻, were released from the materials during immersion, which could impart favourable activities for the implant. This work demonstrated that a simple and novel method could be applied to enhance functionalities of Ti alloys for load-bearing implant applications.

Keywords: Titanium; Fluorapatite; Cladding; Simulated body fluid

Modification of the surface properties of polyimide films using polyhedral oligomeric silsesquioxane deposition and oxygen plasma exposure by Christopher J. Wohl; Marcus A. Belcher; Sayata Ghose; John W. Connell (pp. 8135-8144).

Topographically rich surfaces were generated by spray-coating organic solutions of a polyhedral oligomeric silsesquioxane, octakis(dimethylsilyloxy)silsesquioxane (POSS), on Kapton^® HN films and exposing them to radio frequency generated oxygen plasma. Changes in both surface chemistry and topography were observed. High-resolution scanning electron microscopy indicated substantial modification of the POSS-coated polyimide surface topographies as a result of oxygen plasma exposure. Water contact angles varied from 104° for unexposed POSS-coated surfaces to ∼5° for samples exposed for 5h. Modulation of the dispersive and polar contributions to the surface energy was determined using van Oss Good Chaudhury theory. Changes in surface energy are related to potential adhesive interactions with lunar dust simulant particles.

Keywords: Polyimide; Polyhedral oligomeric silsesquioxane; Oxygen plasma; Lunar dust

Structural, electronic properties and stability of the (1×1) PbTiO₃ (111) polar surfaces by first-principles calculations by Qing Pang; Jian-Min Zhang; Ke-Wei Xu; Vincent Ji (pp. 8145-8152).

Under GGA, the structural, electronic properties and stabilities of four different (1×1) terminations of cubic PbTiO₃ (111) surface, the directly cleaved (111)-Ti and (111)-PbO₃ terminations and the constructed (111)-TiO and (111)-PbO₂ ones, have been systematically studied by using projector-augmented wave method implemented in VASP. For (111)-Ti and (111)-PbO₃ terminations, Ti–O bonds between the outermost two layers are enhanced after relaxation, while those between the second and the third layers are weakened. In addition, a contraction of O–O distance in surface PbO₃ layer is also found for (111)-PbO₃ termination. Moreover, electronic structures of both (111)-Ti and (111)-PbO₂ terminations are significantly influenced by structure relaxations, and the effects of the surface on the DOS are dominantly on the Ti layers, especially the CB. For a constructed (111)-TiO termination, the relaxation results show both Ti–O bonds between the outermost two layers and those between the second PbO₃ layer and the third Ti layers are enhanced. For a constructed (111)-PbO₂ termination, Ti–O bonds between the outermost two layers are also enhanced as in the (111)-TiO termination, however, inequivalent Ti–O bonds between the second layer Ti atom and the third layer O atoms are found, with two bonds expanding and the other one contracting. Results of electronic structure calculations show these two constructed terminations are all insulating and changes of DOS originate dominantly from modifications of surface compositions. Furthermore, it is found that for all four different (111) terminations, the movements of the cation and/or anion on the outermost layer along the surface normal direction after relaxation all result in a reduction of the space electric field. In O and Pb external environments, it is predicted that (111)-PbO₂ termination is the most stable one in O- and Pb-rich environments, however, the (111)-Ti termination is stable one in O- and Pb-poor conditions. The (111)-TiO termination also shows a stability domain in moderate O and Pb environments.

Keywords: PbTiO; ₃; surface; Relaxation; Electronic structure; Stability; First-principles

Ice adhesion on super-hydrophobic surfaces by S.A. Kulinich; M. Farzaneh (pp. 8153-8157).

In this study, ice adhesion strength on flat hydrophobic and rough super-hydrophobic coatings with similar surface chemistry (based on same fluoropolymer) is compared. Glaze ice, similar to naturally accreted, was prepared on the surfaces by spraying super-cooled water microdroplets at subzero temperature. Ice adhesion was evaluated by spinning the samples at constantly increasing speed until ice delamination occurred. Super-hydrophobic surfaces with different contact angle hysteresis were tested, clearly showing that the latter, along with the contact angle, also influences the ice–solid adhesion strength.

Keywords: PACS; 68.35.Md; 68.08.Bc; 82.45.MpHydrophobicity; Ice adhesion; Shear stress; Contact angle hysteresis

Growth of nanocrystalline CuIn₃Se₅ (OVC) thin films by ion exchange reactions at room temperature and their characterization as photo-absorbing layers by Ramphal Sharma; Anil Ghule; Vidya Taur; R. Joshi; Rajaram Mane; J.C. Vyas; Gangri Cai; T. Ganesh; Sun-Ki Min; Wonjoo Lee; Sung-Hwan Han (pp. 8158-8163).

Nanocrystalline CuIn₃Se₅ thin films have been grown on ITO glass substrates using chemical ion exchange reactions with CdS, in alkaline medium at pH 11. The as-deposited films were annealed in air at 200°C for 30min and characterized using X-ray diffraction (XRD), transmission electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and scanning electron microscopy to study the structural, compositional and morphological properties. The XRD patterns reveal the nanoparticles size to be of 18–20nm diameter, while from the SEM images the nanoparticles size is estimated to be 20–30nm. It is observed that the annealed films contain nanocrystallites connected with each other through grain boundaries, with grain size of about 100–125nm and have an overall n-type electrical conductivity and higher photoconductivity. The current–voltage ( I– V) characteristics (in dark and light) of these films indicated the formation of a Schottky like junction between the n-CuIn₃Se₅ (OVC) and CdS/ITO layers.

Keywords: Cation–anion exchange; Nanocrystalline; n; -type CuIn; ₃; Se; ₅; OVC; Photosensitive

Stress induced preferred orientation and phase transition for ternary WC_xN_y thin films by Y.D. Su; C.Q. Hu; C. Wang; M. Wen; D.S. Liu; W.T. Zheng (pp. 8164-8170).

We deposit ternary WC_xN_y thin films on Si (100) substrates at 500°C using direct current (DC) reactive magnetron sputtering in a mixture of CH₄/N₂/Ar discharge, and explore the effects of substrate bias ( V_b) on the intrinsic stress, preferred orientation and phase transition for the obtained films by virtue of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and selective area electron diffraction (SAED). We find that with increasing the absolute value of V_b up to 200V the carbon ( x) and nitrogen ( y) atom concentrations of WC_xN_y films keep almost constant with the values of 0.75 and 0.25, respectively. The XPS and SAED results, combined with the density-functional theory (DFT) calculations on the electronic structure of WC_0.75N_0.25, show our obtained WC_xN_y films are single-phase of carbonitrides. Furthermore, we find that the compressive stress sharply increases with increasing the absolute value of V_b, which leads to a pronounced change in the preferred orientation and phase structure for the film, in which a phase transition from cubic β-WC_xN_y to hexagonal α-WC_xN_y occurs as V_b is in the range of −40 to −120V. In order to reveal the relationship between the stress and phase transition as well as preferred orientation, the DFT calculations are used to obtain the elastic constants for β-WC_xN_y and α-WC_xN_y. The calculated results show that the preferred orientation is dependent on the competition between strain energy and surface energy, and the phase transition can be attributed to a decrease in the strain energy.

Keywords: PACS; 64.70.−p; 62.20.−x; 68.55. −aWC; _x; N; _y; thin films; Stress; Preferred orientation; Phase transition

Ablation mechanism study on metallic materials with a 10ps laser under high fluence by J. Cheng; W. Perrie; B. Wu; S. Tao; S.P. Edwardson; G. Dearden; K.G. Watkins (pp. 8171-8175).

Single shot ablation of metallic materials of aluminium, titanium alloy (Ti6Al4V) and gold has been studied with 10picoseconds (ps) laser pulses experimentally and theoretically. The ablation rate variation at high fluence was explained by a simplified predictive model based on critical-point phase separation (CPPS) theory. A comparison between experimental and numerical results inferred that CPPS may well be the dominant ablation mechanism for high fluence laser ablation at 10ps laser duration.

Keywords: PACS; 52.38.Mf; 52.50.JmPicosecond laser processing; Metals and alloys; Modeling of laser ablation

Attachment of linear poly(amido amine) to silica surface and evaluation of metal-binding behavior by R.K. Dey; Tanushree Patnaik; V.K. Singh; Sanjay K. Swain; Claudio Airoldi (pp. 8176-8182).

The investigation reports preparation of two new adsorbent materials, SiPOLHET and SiPOLHOM, by attachment of linear poly(amido amine) (PAA) to silica surface by adopting heterogeneous and homogeneous modification procedures, respectively. Their structures were characterized by FTIR,¹³C and²⁹Si NMR spectroscopy. Surface morphologies and corresponding elemental composition were determined by using SEM and EDS techniques. The metal binding characteristics of the adsorbents towards Cu²⁺ and Ni²⁺ were studied in dilute aqueous solution which presents an interesting aspect of increasing trend.

Keywords: Adsorbent; Silica; Poly(amido amine); Adsorption

Pyrolysis of cellulose and lignin by T. Haensel; A. Comouth; P. Lorenz; S. I.-U. Ahmed; S. Krischok; N. Zydziak; A. Kauffmann; J.A. Schaefer (pp. 8183-8189).

X-ray and UV-induced photoelectron spectroscopy (XPS and UPS) and scanning electron microscopy (SEM) have been performed to characterise the pyrolysis of cellulose and lignin and their interaction with methanol. Clean highly oriented pyrolitic graphite (HOPG) was also analysed as a reference material. Asymmetric C1s core level fits and valence band XPS of the samples indicate a graphitic-like structure after the pyrolysis at 1200°C. Due to the low polar contents in pyrolysed cellulose and lignin, an interaction with methanol under high vacuum conditions could not be identified. From a technical viewpoint a temperature of 1200°C is attainable without high costs. Therefore, the pyrolysis of wood-based polymers containing high amounts of cellulose and lignin are potential low-cost materials for various applications. If it is possible to generate graphite in complex structures made of wood-based polymers, a cheap and energy-efficient method will become available for producing bipolar plates for fuel cells. Technical problems like form instability and foaming are discussed as well as further development and possible modifications of the ground material to achieve optimal compositions.

Keywords: Cellulose; Lignin; Pyrolysis; XPS; UPS; HOPG; Valence band; Methanol; VB

Interdiffusion reaction in the CrN interlayer in the NiCrAlY/CrN/DSM11 system during thermal treatment by W.Z. Li; Q.M. Wang; J. Gong; C. Sun; X. Jiang (pp. 8190-8193).

During thermal treatment, a series of chemical reactions took place in the CrN interlayer in the NiCrAlY/CrN/DSM11 system. The CrN phase in the interlayer was first transformed to intermediate AlN and Cr₂N phases during vacuum heat treatment, and thereafter both changed to TiN phase after thermal exposure. The formation of TiN is beneficial to the suppression of elemental interdiffusion. With the good barrier ability and strong interfacial bonding, the CrN interlayer acts as an excellent diffusion barrier.

Keywords: PACS; 81.15.HiInterdiffusion; CrN; Diffusion barrier; Interfacial strength; Coatings

Erratum to “Analysis of XPS spectra of Fe²⁺ and Fe³⁺ ions in oxide materials” [Appl. Surf. Sci. 254 (2008) 2441–2449] by Toru Yamashita; Peter Hayes (pp. 8194-8194).

Erratum to “Effect of annealing atmosphere on the photoluminescence of ZnO nanospheres” [Appl. Surf. Sci. 255 (2009) 4801–4805] by Yongzhe Zhang; Yanping Liu; Lihui Wu; Hui Li; Lizhong Han; Bochong Wang; Erqing Xie (pp. 8195-8195).

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Applied Surface Science (v.255, #18)