Applied Surface Science (v.254, #17)
Preparation of transparent BN films with superhydrophobic surface by Guo-Xing Li; Yi Liu; Bo Wang; Xue-Mei Song; Er Li; Hui Yan (5299-5303).
A novel approach was investigated to obtain the superhydrophobicity on surfaces of boron nitride films. In this method boron nitride films were deposited firstly on Si(1 0 0) and quartz substrate using a radio frequency (RF) magnetron sputtering system, and then using CF4 plasma treatment, the topmost surface area can be modified systematically. The results have shown that the water contact angle on such surfaces can be tuned from 67° to 159°. The films were observed to be uniform. The surfaces of films consist of micro-features, which were confirmed by Atomic Force Micrograph. The chemical bond states of the films were determined by Fourier Transform Infrared (FTIR) Spectroscopy, which indicate the dominance of B–N binding. According to the X-ray Photoelectron Spectroscopy analysis, the surface of film is mainly in BN phase. The micro-feature induced surface roughness is responsible for the observed superhydrophobic nature. The water contact angles measured on these surfaces can be modeled by the Cassie's formulation.
Keywords: Superhydrophobic surface; BN films; Plasma etching; Wettability;
Study on preparation and fluorescence characteristic of coordinated Eu2O3/polymer hybrid films by Qian-huo Chen; Si-ning Zheng; Can-hu Huang; Wen-gong Zhang (5304-5313).
The cyclohexane solution of TTA (trifluorothenoyl-acetone), phen (8-hydroxylquinoline) and PS (polystyrene), the ethyl acetate solution of TTA, phen and PMMA (polymethyl methacrylate) were used as flowing liquid, the coordinated Eu2O3/polymer hybrid colloids were successively produced by focused pulsed laser ablation of Eu2O3 target in interface of solid and flowing liquid. As solvent in the hybrid colloids has volatilized, the coordinated Eu2O3/polymer hybrid films were obtained. The hybrid colloids and films were characterized by TEM, UV–vis spectrum, fluorescence spectrum, TG-FTIR and X-ray photoelectron spectrum. The results show the coordinated Eu2O3 nanoparticles with average size of less than 20 nm are surrounded by the three-dimensional network and are properly incorporated into the PMMA and PS matrix, the hybrid films can emit intense red light under ultraviolet radiation, and their emission fluorescence spectra display same characteristic emission peaks of Eu3+ ions. The Eu2O3 hybrid films have better thermo stability than the related pure polymers because of strong interaction between surface europium ions of the nanoparticles and polymer. Because the coordinated Eu2O3 nanoparticles were wrapped by polymer, they have higher chemical stability than the related europium complex.
Keywords: Coordinated Eu2O3; Nanoparticles; Colloids; Polymer; Hybrid film; Fluorescence;
Surface modification of Sylgard 184 polydimethylsiloxane by 254 nm excimer radiation and characterization by contact angle goniometry, infrared spectroscopy, atomic force and scanning electron microscopy by Emanuel A. Waddell; Stephen Shreeves; Holly Carrell; Christopher Perry; Branden A. Reid; James McKee (5314-5318).
The modification of polydimethylsiloxane (PDMS) by narrow band 254 nm excimer radiation under a nitrogen atmosphere was characterized by contact angle goniometry, attenuated total reflectance infrared spectroscopy, atomic force and scanning electron microscopy. UV irradiation results in the formation of the carboxylic acids that influences the wettability of the surface. Continued exposure results in the formation of an inorganic surface (SiO x (1 < x < 2)) which hinders the ability to continually increase the wettability. The continuity of this inorganic layer is disrupted by the formation of surface cracks. These results have implications in the fabrication and chemical modification of microfluidic or micro-electro-mechanical systems.
Keywords: Polydimethylsiloxane; Surface modification; Excimer; Contact angle; Wettability; Microscopy;
Study of structural and electronic environments of hydrogenated amorphous silicon carbonitride (a-SiCN:H) films deposited by hot wire chemical vapor deposition by Bibhu P. Swain; Nong M. Hwang (5319-5322).
Hydrogenated amorphous silicon carbon nitride (a-SiCN:H) thin films were deposited by hot wire chemical vapor deposition (HWCVD) using SiH4, CH4, NH3 and H2 as precursors. The effects of the H2 dilution on structural and chemical bonding of a-SiCN:H has been investigated by Raman and X-ray photoelectron spectroscopy (XPS). Increasing the H2 flow rate in the precursor gas more carbon is introduced into the a-SiCN:H network resulting in decrease of silicon content in the film from 41 at.% to 28.8 at.% and sp2 carbon cluster increases when H2 flow rate is increased from 0 to 20 sccm.
Keywords: a-SiCN:H; XPS; Raman spectroscopy;
Functionalization of hydrogen-free diamond-like carbon films using open-air dielectric barrier discharge atmospheric plasma treatments by J.L. Endrino; J.F. Marco; M. Allen; P. Poolcharuansin; A.R. Phani; J.M. Albella; A. Anders (5323-5328).
A dielectric barrier discharge (DBD) technique has been employed to produce uniform atmospheric plasmas of He and N2 gas mixtures in open air in order to functionalize the surface of filtered-arc deposited hydrogen-free diamond-like carbon (DLC) films. XPS measurements were carried out on both untreated and He/N2 DBD plasma-treated DLC surfaces. Chemical states of the C 1s and N 1s peaks were collected and used to characterize the surface bonds. Contact angle measurements were also used to record the short- and long-term variations in wettability of treated and untreated DLC. In addition, cell viability tests were performed to determine the influence of various He/N2 atmospheric plasma treatments on the attachment of osteoblast MC3T3 cells. Current evidence shows the feasibility of atmospheric plasmas in producing long-lasting variations in the surface bonding and surface energy of hydrogen-free DLC and consequently the potential for this technique in the functionalization of DLC-coated devices.
Keywords: Ion implantation and deposition; DLC; XPS; Wettability; Cell viability;
Developing a novel fluorescence chemosensor by self-assembly of Bis-Schiff base within the channel of mesoporous SBA-15 for sensitive detecting of Hg2+ ions by Jianqiang Wang; Li Huang; Min Xue; Long Liu; Ying Wang; Ling Gao; Jianhua Zhu; Zhigang Zou (5329-5335).
A novel fluorescence chemosensor for Hg2+ ion has been developed by the assembly of fluorescence Bis-Schiff base PMBA within the channels of CPTES-modified SBA-15. The ordered porous structure of SBA-15 is still retained on the hybrid chemosensor material PMBA-SBA. A remarkable fluorescence quenching of PMBA-SBA by Hg2+ ion was attributed to heavy atom effect of Hg2+ ion. The linear detecting range of the hybrid mesoporous chemosensor for Hg2+ ion is 2–15 μM and the lowest detection limit is 0.6 μM in ethanol/water (9:1, v/v) solution.
Keywords: Chemosensor; Mesoporous material; Fluorescence mercury ion; Quenching;
X-ray photoelectron spectroscopic studies on oxidation behavior of nickel and iron aluminides under oxygen atmosphere at low pressures by Naofumi Ohtsu; Akiko Nomura; Masaoki Oku; Toetsu Shishido; Kazuaki Wagatsuma (5336-5341).
Oxidation behaviors of NiAl, Ni3Al, and FeAl under oxygen atmosphere at low pressures were studied by X-ray photoelectron spectroscopy (XPS). Clean surfaces of these aluminides were prepared by fracturing in an ultra high vacuum, and then the fractured surfaces were oxidized by exposing to high-purity oxygen at pressures up to 1.3 Pa without exposing to air. The oxides formed on NiAl and FeAl surfaces were Al2O3, whereas the oxide on Ni3Al was NiAl2O4. Aluminum, nickel, and iron on clean surfaces were oxidized even at a pressure of 1.3 × 10−6 Pa. The oxidation evolves with an increase in the pressure of oxygen, and further oxidation of aluminum occurs prior to that of nickel or iron. The oxidation behaviors under such oxygen atmosphere were similar to those of the aluminides oxidized in air, and these behaviors could be predicted from thermodynamic consideration.
Keywords: X-ray photoelectron spectroscopy; Nickel and iron aluminides; Oxidation behavior under oxygen atmosphere;
The effect of interphase modification on carbon fiber/polyarylacetylene resin composites by L. Liu; Y.J. Song; H.J. Fu; Z.X. Jiang; X.Z. Zhang; L.N. Wu; Y.D. Huang (5342-5347).
Interfacial modification for carbon fiber (CF) reinforced polyarylacetylene (PAA) resin, a kind of non-polar, was investigated. The high carbon phenolic resin was used as coating to treat the surface of CF after oxidation. Atomic force microscopy (AFM) with force modulation mode was used to analyze the interphase of composite. The interlaminar shear strength (ILSS) and mechanical properties of CF/PAA composites were also measured. It was found that the CF/PAA composites treated with oxidation and coating after oxidation had transition area between carbon fiber and PAA resin. The existence of transition area led to the improvement of interfacial performance of composites. Specially, the thickness and stiffness of interphase of composite treated with coating after oxidation were more suitable for CF/PAA composites. Thus, the composite treated with coating after oxidation had the highest value of ILSS and the best mechanical properties.
Keywords: Atomic force microscopy; Interphase; Polyarylacetylene resin; Coating;
Surface composition modification of high-carbon low-alloy steels oxidized at high temperature in air by D. Genève; D. Rouxel; P. Pigeat; B. Weber; M. Confente (5348-5358).
Segregating alloys across a metal/oxide interface, which occurs when an iron alloy is heated at high temperature in air, was studied on five high-carbon low-alloy steels. The metallographic analyses showed differences between the oxidation kinetics, the decarburisation rates of the surfaces and the number of surface defects. The results of the AES analyses enabled the characterization of the concentration profiles of the alloy elements and to explain the differences observed between the oxidation kinetics, the decarburisation rates and the number of surface defects. All the concentration profiles are discussed and possible mechanisms are proposed in order to understand the profiles obtained.
Keywords: Iron alloys; Grain boundary embrittlement; Interface segregation; Oxidation; Auger electron spectroscopy (AES);
Preparation of uniform porous hydroxyapatite biomaterials by a new method by YueJun Tang; YueFeng Tang; ChunTang Lv; ZhongHua Zhou (5359-5362).
In this paper, a new method of preparation of uniform porous hydroxyapatite biomaterials was reported. In order to obtain uniform porous biomaterials, disk samples were formed by the mixture of hydroxyapatite (HAP) powders and monodispersed polystyrene microspheres, and then HAP uniform porous materials with different diameter and different porosity (diameter: 436 ± 25 nm, 892 ± 20 nm and 1890 ± 20 nm, porosity: 46.5%, 41.3% and 34.7%, respectively) were prepared by sintering these disk samples at 1250 °C for 5 h. The pure phase of HAP powders fabricated by the hydrothermal technology was confirmed by X-ray diffraction (XRD). The surface and size distribution of pores in HAP biomaterials were observed by scanning electron microscopy (SEM), and the pore size distribution in porous HAP biomaterials was tested by mercury intrusion method.
Keywords: HAP; Uniform pores; Porous biomaterials; Monodispersed polystyrene microspheres; Mercury intrusion method; Sintering;
Thermal annealing effects on a compositionally graded SiGe layer fabricated by oxidizing a strained SiGe layer by Kunhuang Cai; Cheng Li; Yong Zhang; Jianfang Xu; Hongkai Lai; Songyan Chen (5363-5366).
Thermal annealing effects on a thin compositionally graded SiGe buffer layer on silicon substrate fabricated by oxidizing a strained SiGe layer are investigated with X-ray diffraction, ultraviolet Raman spectra and atomic force microscopy. Interestingly, we found that the surface roughness and the threading dislocation densities are kept low during the whole annealing processes, while the Ge concentration at the oxidizing interface decreases exponentially with annealing time and the strain in the layer is only relaxed about 66% even at 1000 °C for 180 min. We realized that the strain relaxation of such a compositionally graded SiGe buffer layer is dominated by Si–Ge intermixing, rather than generation and propagation of misfit dislocations or surface undulation.
Keywords: SiGe; Thermal annealing; Si–Ge intermixing; Strain relaxation;
Surface-modified zeolite-filled chitosan membranes for pervaporation dehydration of ethanol by Honglei Sun; Lianyu Lu; Xue Chen; Zhongyi Jiang (5367-5374).
Surface-modified zeolite-filled chitosan (CS) membranes were prepared by incorporating 3-mercaptopropyltrimethoxysilane (MPTMS)-modified H-ZSM-5 zeolite into chitosan for pervaporation dehydration of aqueous ethanol solution. The physicochemical characterization by XPS, FT-IR, XRD, DMA and SEM showed that –SO3H group was readily grafted on the surface of H-ZSM-5 with the mediation of MPTMS and hydrogen peroxide, and the accompanying ion–ion interaction between –SO3H group on surface-modified H-ZSM-5 and –NH3 + group on chitosan substantially eliminated the nonselective voids at the chitosan–H-ZSM-5 interface of the filled membranes. The experimental results also revealed that H-ZSM-5 exhibited desirable size-selective and preferential adsorption effects for aqueous ethanol solution. As a result, modified H-ZSM-5 filled membranes showed higher swelling degree and permeation flux, and improved selectivity for aqueous ethanol solution. In comparison between chitosan control membrane (permeation flux 54.18 g/(m2 h) and separation factor 158.02 for 90 wt.% aqueous ethanol solution at 80 °C), the modified H-ZSM-5 filled membrane with 8 wt.% filling content exhibited a remarkably improved pervaporation performance with permeation flux 278.54 g/(m2 h) and separation factor 274.46 under the identical experimental condition.
Keywords: Zeolite; 3-Mercaptopropyltrimethoxysilane; Membrane; Pervaporation; Ethanol dehydration;
Reasons for the deactivation of Pt0/TiO2 photocatalyst treated by inert gas N2 by Jingju Wang; Min Zhang; Ke Wang; Jiwei Zhang; Zhishen Wu; Zhensheng Jin (5375-5379).
The effect of N2 treatment on the photocatalytic activity of Pt0/TiO2 was investigated. The results showed that after treatment at 500 °C in N2, 70% of the photocatalytic activity of 1.0 wt.% Pt0/TiO2 was lost by the evaluation of photocatalytic oxidation reaction of C3H6. Transmission electron microscopy (TEM) and Ar+ ion sputtering tests revealed that in the course of high-temperature N2 treatment, the size of Pt0 particles on TiO2 increases and a strong interaction between metal and support, i.e. Pt0 particles encapsulated by Ti x O y , happens, which are the reasons for the deactivation of Pt0/TiO2 photocatalyst treated by high-temperature N2.
Keywords: Pt0/TiO2; C3H6 photocatalytic oxidation; Encapsulation; Strong metal–support interaction (SMSI);
Carbon monoxide adsorption on Pd-deposited Cu(1 1 0) surface: Infrared reflection absorption and temperature programmed desorption studies by T. Wadayama; H. Osano; H. Yoshida; S. Oda; N. Todoroki (5380-5384).
We investigated carbon monoxide (CO) adsorption and desorption behaviors on 0.1-nm-, 0.15-nm-, and 0.3-nm-thick-Pd-deposited Cu(1 1 0) surfaces using infrared reflection absorption (IRRAS) and temperature-programmed desorption (TPD) spectroscopic methods. CO was exposed to the 0.1-nm-thick-Pd/Cu(1 1 0) surface at the substrate temperature of 90 K. The IR band attributable to CO bonded to Cu atoms emerged at 2092 cm−1: the band was located at 2100 cm−1 at saturation coverage, with a shoulder at 2110 cm−1. In addition to these bands, weak absorptions attributable to the Pd―CO bonds appeared at 2050 and 1960 cm−1. With increasing Pd thickness, the Pd related-bands became increasingly prominent. Particularly at the early stage of exposure, the band at 2115 cm−1 became visible. The band at 2117 cm−1 dominated the spectra all through the exposures for the 0.3-nm-thick-Pd surface. The TPD spectra of the surfaces showed two remarkable features at around 220–250 and 320–390 K, ascribable ,respectively, to Cu―CO and Pd―CO. The desorption peaks shifted to higher temperatures with increasing Pd thickness. Based on the TPD and IRRAS results, we discuss the adsorption–desorption behaviors of CO on the Pd/Cu(1 1 0) surfaces.
Keywords: Palladium; Copper; Infrared absorption spectroscopy; Thermal desorption spectroscopy; Carbon monoxide; Cu(1 1 0);
Passivation of GaAs surface by atomic-layer-deposited titanium nitride by M. Bosund; A. Aierken; J. Tiilikainen; T. Hakkarainen; H. Lipsanen (5385-5389).
The suitability of titanium nitride (TiN) for GaAs surface passivation and protection is investigated. A 2–6-nm thick TiN passivation layer is deposited by atomic layer deposition (ALD) at 275 ° C on top of InGaAs/GaAs near surface quantum well (NSQW) structures to study the surface passivation. X-ray reflectivity measurements are used to determine the physical properties of the passivation layer. TiN passivation does not affect the surface morphology of the samples, but increases significantly the photoluminescence intensity and carrier lifetime of the NSQWs, and also provides long-term protection of the sample surface. This study shows that ALD TiN coating is a promising low-temperature method for ex situ GaAs surface passivation.
Keywords: Atomic layer deposition; Gallium arsenide; Photoluminescence; Surface passivation; Titanium nitride;
Synthesis and characterization of vanadium nanoparticles on activated carbon and their catalytic activity in thiophene hydrodesulphurization by Susana Pinto; Lindora D’Ornelas; Paulino Betancourt (5390-5393).
Vanadium nanoparticles (∼7 nm) stabilized on activated carbon were synthesized by the reduction of VCl3·3THF with K[BEt3H]. This material was characterized by inductive coupled plasma-atomic emission spectroscopy (ICP-AES), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) analyses. The catalytic performance of the carbon-supported vanadium was studied using thiophene hydrodesulfurization (HDS) as model reaction at 300 °C and P = 1 atm. The catalytic activity of the vanadium carbide phase on the activated carbon carrier was more significant than that of the reference catalysts, alumina supported NiMoS. The method proposed for the synthesis of such a catalyst led to an excellent performance of the HDS process.
Keywords: Nanoparticles; Vanadium carbide; V2O3; Hydrodesulphurization;
Synthesis and characterization of nanostructured bimetallic films on α-Al2O3 substrates using electroless deposition by Baoquan Zhang; Ruijie Guo; Xiufeng Liu (5394-5398).
The Pt–Pd and Pd–Ag nanostructured bimetallic films on porous α-Al2O3 substrates are successfully synthesized by chemical deposition using lyotropic liquid crystalline templating strategy. The co-reduction of two metallic species in the presence of liquid crystalline phase by hydrazine hydrate produces hexagonal nanostructured Pt–Pd and lamellar nanostructured Pd–Ag films. Low-angle X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies show the ordered nanostructure of both Pt–Pd and Pd–Ag films. The energy dispersive X-ray (EDX) and wide-angle XRD analyses of the bimetallic films have verified the coexistence and uniform distribution of constituent metallic species. By taking into account of catalytic activities, well-defined nanochannels and higher surface areas, the nanostructured bimetallic films might have application potential in microreactors.
Keywords: Nanomaterial; Liquid crystalline template; Thin film;
Silver fractal networks for surface-enhanced Raman scattering substrates by T. Qiu; X.L. Wu; J.C. Shen; Y. Xia; P.N. Shen; Paul K. Chu (5399-5402).
Based on diffusion-limited aggregation process, a convenient nanotechnique is demonstrated to obtain large silver fractal networks for a surface-enhanced Raman scattering (SERS)-active substrate. The silver fractal networks are of high SERS enhancement factor, large dynamical range. The observed SERS efficiency can be explained in terms of strongly localized plasmon modes relative to the single particle plasmon resonance.
Keywords: Silver fractal networks; Surface-enhanced Raman scattering;
Formation of ZnO and Zn1−x Cd x O films on CdTe/CdZnTe single crystals by J.L. Plaza; O. Martínez; V. Carcelén; J. Olvera; L.F. Sanz; E. Diéguez (5403-5407).
In this work we report on the properties of ZnO and Zn1−x Cd x O films formed on top of CdTe and CdZnTe single crystals. The films have been obtained by thermal evaporation of Zn metal films and further oxidation in atmospheric conditions. The structural and compositional characteristics of the films have been analysed by means of scanning electron microscopy and energy-dispersive X-ray analysis. The chemical composition of the films as a function of growth parameters has been obtained. It has been possible to demonstrate by Raman spectroscopy the formation of both ZnO and Zn1−x Cd x O films. The possible inter-diffusion effects between the films and the substrate, derived from the oxidation process, have been discussed. It has been possible to check by means of photoluminescence, the optical quality of the ZnO and Zn1−x Cd x O films, also regarding to the presence of local changes. Differences between the optical spectra obtained from various ZnO films grown on top of CdTe and CdZnTe substrates enabled the determination of compositional differences introduced by the substrate when the deposition parameters are modified.
Keywords: Zinc oxide; Cadmium telluride;
Hydrolysis–condensation reactions of titanium alkoxides in thin films: A study of the steric hindrance effect by X-ray photoelectron spectroscopy by Vincent Barlier; Véronique Bounor-Legaré; Gisèle Boiteux; Joël Davenas; Didier Léonard (5408-5412).
An original approach based on X-ray photoelectron spectroscopy (XPS) is proposed to study the influence of the surrounding humidity on the hydrolysis–condensation reactions of five titanium alkoxides in thin films. More precisely, the influence of the nature of the ligands (propoxide, butoxide, isopropoxide, phenoxide, and 9H-carbazole-9-yl-ethyl-oxy) on the reaction rate was evidenced. The reaction advancement was evaluated by comparing XPS chemical compositions to theoretical compositions calculated for all the possible rates. XPS chemical environment information allowed validating the reliability of this approach through the evaluation of the condensation state. In both approaches, the influence of the steric hindrance on the reactivity of titanium alkoxides was highlighted to be similar to what has been previously observed in solution. Theses results corroborate the validity of our XPS approach to determine titanium alkoxide hydrolysis–condensation reactions in the specific application of thin films.
Keywords: Titanium alkoxide; Hydrolysis–condensation; Thin films; X-ray photoelectron spectroscopy;
Effect of alkali leaching on the surface structure of Ni3Al catalyst by Ya Xu; Masahiko Demura; Toshiyuki Hirano (5413-5420).
The surface structure of the alkali-leached single-phase Ni3Al powder was investigated by X-ray diffraction, BET (Brunauer–Emmett–Teller) surface area analysis, electron microscopy, X-ray photoelectron spectroscopy, and temperature-programmed reduction. It was found that fine Ni particles of several nm in diameter were formed on the outer surface layer of the Ni3Al powder after the alkali leaching process. The surface of the Ni particles was covered with a thin layer of Ni oxides and hydroxide, Ni2O3, NiO and Ni(OH)2, and these Ni oxides and hydroxide can be easily reduced by hydrogen to the metallic nickel that is catalytically active. The inside of the Ni3Al powder remained as the original Ni3Al ordered structure after alkali leaching. Having heat resistant properties, the Ni3Al phase can serve as a support of the fine Ni particles and provide the structural and thermal stabilities to the fine Ni particles.
Keywords: Intermetallic compounds; Ni-Al catalysts; Alkali leaching;
In situ endpoint detection of reactive ion-beam etching of dielectric gratings with an etch-stop layer using downstream mass spectrometry by Xiangfeng Meng; Lifeng Li (5421-5425).
Downstream mass spectrometry is successfully used in the reactive ion-beam etching of dielectric diffraction gratings of deep grooves with vertical sidewalls to achieve in situ endpoint detection. Silica (SiO2) gratings with a Sc2O3 etch-stop layer are fabricated by reactive ion-beam etching with CHF3 as etchant, and the mass spectrometric signal of SiF3 + produced by the reactive etching of the SiO2 grating material is monitored. When the etch-stop layer is reached, a drop of this signal occurs. By comparing the monitoring curves and resulting gratings of different etching methods, we find that the decrease of the monitored signal is strongly influenced by the sidewall steepness of the etched grating grooves. All conditions being equal, the greater sidewall steepness renders the faster decrease of the signal. Consequently, the proposed approach of endpoint detection applies well to the gratings with steep sidewalls. With the help of two previously developed methods, the sidewall steepness of grating grooves is increased, and the optimal endpoint is detected. Employing the proposed technique, we have reproducibly fabricated dielectric gratings with proper groove depth and even groove bottom.
Keywords: Endpoint detection; Reactive ion-beam etching; Dielectric gratings; Mass spectrometry;
Enhanced field emission from ZnO nanopencils by using pyramidal Si(1 0 0) substrates by Jing Xiao; Yue Wu; Wei Zhang; Xin Bai; Ligang Yu; Shiqi Li; Gengmin Zhang (5426-5430).
Zinc oxide nanopencil arrays were synthesized on pyramidal Si(1 0 0) substrates via a simple thermal evaporation method. Their field emission properties have been investigated: the turn-on electric field (at the current density of 10 μA/cm2) was about 3.8 V/μm, and the threshold electric field (at the current density of 1 mA/cm2) was 5.8 V/μm. Compared with similar structures grown on flat Si substrates, which were made as references, the pyramidal Si-based ZnO nanopencil arrays appeared to be superior in field emission performance, thus the importance of the non-flat substrates has been accentuated. The pyramidal Si substrates could not only suppress the field screening effect but also improve the field enhancement effect during the field emission process. These findings indicated that using non-flat substrates is an efficient strategy to improve the field emission properties.
Keywords: Field emission; Zinc oxide; Nanostructures; Chemical vapor deposition;
AFM tip-induced ripple pattern on AIII-BV semiconductor surfaces by B. Such; F. Krok; M. Szymonski (5431-5434).
Modification of c(8x2) InSb(0 0 1) surface induced by prolonged scanning with an atomic force microscope tip has been investigated. The experiment performed with loads of few tens of nanoNewtons resulted in creation of ripples perpendicular to the fast scan direction. It was found that terrace edges are acting as initial instabilities leading to development of the ripple pattern. As a result, information about initial surface topography is preserved in the ripple amplitude, even so the final height of the ripples and their periodicity are determined by the tip curvature.
Keywords: AFM; Wear; InSb;
Surface depth analysis for fluorinated block copolymer films by X-ray photoelectron spectroscopy using C60 cluster ion beam by Keiji Tanaka; Noriaki Sanada; Masaya Hikita; Tetsuya Nakamura; Tisato Kajiyama; Atsushi Takahara (5435-5438).
X-ray photoelectron spectroscopy (XPS) using fullerene (C60) cluster ion bombardment was applied to films of a fluorinated block copolymer. Spectra so obtained were essentially different from those using Ar ion beam. Structure in the surface region with the depth down to 60 nm drawn on the basis of XPS with C60 beam was essentially the same as the one drawn by the result using dynamic secondary ion mass spectrometry, which is a well-established method for the depth analysis of polymers. This implies that XPS using C60 beam enables one to gain access to the depth analysis of structure in polymer films with the depth range over the analytical depth of conventional XPS, that is, three times inelastic mean-free path of photoelectrons.
Keywords: XPS; DSIMS; C60 cluster ion beam; Fluorinated block copolymer;
Structural, optical properties and band gap alignments of ZrO x N y thin films on Si (1 0 0) by radio frequency sputtering at different deposition temperatures by L.Q. Zhu; Q. Fang; X.J. Wang; J.P. Zhang; M. Liu; G. He; L.D. Zhang (5439-5444).
ZrO x N y thin films have been prepared by radio frequency magnetron sputtering at various substrate temperatures. The effect of substrate temperature on structural, optical properties and energy-band alignments of as-deposited ZrO x N y thin films are investigated. Atomic force microscopy results indicate the decreased root-mean-square (rms) values with substrate temperature. Fourier transform infrared spectroscopy spectra indicate that an interfacial layer has been formed between Si substrate and ZrO x N y thin films during deposition. X-ray photoelectron spectroscopy and spectroscopy ellipsometry (SE) results indicate the increased nitrogen incorporation in ZrO x N y thin films and therefore, the decreased optical band gap (E g) values as a result of the increased valence-band maximum and lowered conduction-band minimum.
Keywords: X-ray photoelectron spectroscopy (XPS); Sputtering; Spectroscopy ellipsometry; Band-offset;
Chemisorption of hydrogen sulphide on zinc oxide modified aluminum-substituted SBA-15 by Xiaohui Wang; Jinping Jia; Ling Zhao; Tonghua Sun (5445-5451).
Aluminum silicate mesoporous material, ZnO/Al–SBA-15, was synthesized by post-synthesis and immobilization method via microwave-assisted route. Desulphurization tests from a gas mixture with low content H2S were carried out as the probing reaction on these materials. Chemical effects and the nature of the ZnO additive and textural properties on desulphurization capacity were studied over this material. Material was characterized using N2 adsorption, XRD, TEM, FTIR, XPS, ICP and other techniques. The analysis suggests that the as-synthesized material had well-ordered hexagonal mesopores and was abundant in micropores. ZnO nanoparticles dispersed well and anchored both in the channel and the wall of mesoporous silica. The material with 2.1 wt.% zinc loading presented the highest H2S uptake capacity. Both micropores and mesopores are active sites for H2S capture, especially micropores. The enhancement of H2S removal capacity was attributed to the integration of the pore structure of mesoporous material and the promising desulphurization properties of ZnO nanoparticles. ZnO/Al–SBA-15 could be an effective alternative to remove H2S from gaseous streams and it also extends the research of mesoporous material.
Keywords: Adsorption; Hydrogen sulphide; Mesostructure; Desulphurization; Zinc oxide nanostructure;
Nanocomposite of polypyrrole and alumina nanoparticles as a coating filler for the corrosion protection of aluminium alloy 2024-T3 by Dennis E. Tallman; Kirill L. Levine; Chavanin Siripirom; Victoria G. Gelling; Gordon P. Bierwagen; Stuart G. Croll (5452-5459).
Aluminium (Al) alloys such as 2024-T3 are widely used in industry as low weight construction materials with excellent mechanical properties. Until recently corrosion protection of Al alloys was carried out with coatings containing hexavalent chromium (Cr6+). However, Cr6+ is a health and environmental hazard and has to be replaced. Intrinsically conducting polymer (ICP) technology is the promising alternative to chromate coating technology because of good corrosion protection properties of ICPs, their moderate cost and good environmental compatibility. In this paper we report successful attempt of making nanocomposite comprised of alumina nanoparticles modified by polypyrrole for the purpose of corrosion protection of Al alloy. Modified nanoparticles were used as coating filler. Coating was designated to perform as an active barrier to electrolyte diffusion. Properties of the coating were examined by adhesion test, electrochemical impedance spectroscopy, X-rays elemental analysis, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy.
Keywords: Coatings; Aluminium alloys; Corrosion; Nanocomposite; Polypyrrole;
Investigation of material properties of thin copper films through finite element modelling of microindentation test by R. Iankov; S. Cherneva; D. Stoychev (5460-5469).
Technology processes of thin metal films deposition are entailed with changes in material’s microstructure. As a result, deposited films often are characterized with material properties, which are different from these of the original bulk material. Determination of these material characteristics is of big importance for practice. In the present work the material properties of thin bright copper film with known depth were investigated. The film was deposited electrochemically over substratum composed of metallurgic brass alloy (CuZn36). Based on the results from microindentation test the load–displacement curve is obtained after the indenter is unloaded and the imprint diameter is measured. Consequently the process of indentation was modelled numerically. The numerical simulation is based on the finite element model of the indentation process. As a result of the simulation the load–displacement curve was obtained numerically for a certain set of material parameters. The trial–error approach is applied to find most appropriate set which fit the experimental load–displacement curve. At the end results, which were obtained through numerical simulation give good coincidence with the experiment. Therefore the proposed method can be successfully applied for identification of material parameters of the accepted model. The proposed trial–error approach is appropriate for investigation of thin films with known thickness, deposited on a substrate with known material characteristics.
Keywords: Thin films; Microindentation test; Finite-element method; Load–displacement curve;
Erosion behavior of EEDS cermet coatings by Jin Guo; Xu Bin-shi; Wang Hai-dou; Yin Liang; Li Qing-fen; Wei Shi-cheng; Cui Xiufang (5470-5474).
This paper investigates the erosion performance of electro-thermal explosion directional spraying (EEDS) cermet WC/Co coatings using an air solid particle erosion rig. The influences of the different parameters such as impact angle, impingement velocity, environment temperature, particle diameter, on the erosion property of the coatings were studied. The eroded surfaces were examined by scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS) and the erosion mechanisms were discussed. The structure and bond characters of the coatings were also determined by transmission electron microscopy (TEM), X-ray diffraction (XRD) and SEM.The results indicate that the EEDS WC/Co coatings are characterized by fine grain structure, good metallurgical bond and brittle erosion character. The erosion rates of the coatings decrease with temperature increasing and increase with impact angle and impingement velocity increasing. At elevated temperature, the oxidation happens on the coatings surface, which affects the erosion behavior.
Keywords: Erosion; Structure; TEM; EEDS; Cermet coating;
Structural and morphological properties of thin ZnO films grown by pulsed laser deposition by M. Suchea; S. Christoulakis; C. Tibeica; M. Katharakis; N. Kornilios; T. Efthimiopoulos; E. Koudoumas (5475-5480).
The pulsed laser deposition technique was used to produce zinc oxide thin films onto silicon and Corning glass substrates. Homogeneous surfaces exhibiting quite small Root Mean Square (RMS) roughness, consisting of shaped grains were obtained, their grain diameters being 40–90 nm at room temperature and at 650 °C growth respectively. Films were polycrystalline, even for growth at room temperature, with preferential crystallite orientation the (0 0 2) basal plane of wurtzite ZnO. Temperature increase caused evolution from grain to grain agglomeration structures, improving crystallinity. Compressive to tensile stresses transition with temperature was found while the lattice constant decreased.
Keywords: Laser deposition; Atomic force microscopy (AFM); Transmission electron microscopy (TEM); X-ray diffraction (XRD); Thin films coatings;
Structure and electrical properties of CdIn2O4 thin films prepared by DC reactive magnetron sputtering by F.F. Yang; L. Fang; S.F. Zhang; J.S. Sun; Q.T. Xu; S.Y. Wu; J.X. Dong; C.Y. Kong (5481-5486).
CdIn2O4 thin films were prepared by direct-current (DC) reactive magnetron sputtering. The structure, surface morphology and the chemical composition of the thin films were analyzed by X-ray diffraction (XRD), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS), respectively. The electrical properties of the films prepared in different oxygen concentration and annealing treatment were determined, and the effects of the preparing conditions on the structure and electrical properties were also explored. It indicates that the CdIn2O4 thin films with uniform and dense surface morphology contain mainly CdIn2O4, In2O3 phases, and CdO phase is also observed. The XPS analysis confirms the films are in oxygen-deficient state. The electrical properties of these films significantly depend on the preparing conditions, the resistivity of the films with the oxygen concentration of 4.29% is 2.95 × 10−4 Ω cm and the Hall mobility is as high as 60.32 cm2/V s. Annealing treatment can improve the electrical performance of the films.
Keywords: CdIn2O4 thin films; Structure; Electrical properties; DC reactive magnetron sputtering;
Gadolinium oxide high-k gate dielectrics prepared by anodic oxidation by P.Y. Kuei; C.C. Hu (5487-5491).
The growth and properties of gadolinium oxide (Gd2O3) films prepared by anodic oxidation were investigated. Uniform Gd2O3 thin film with good oxide quality was obtained. The X-ray diffraction (XRD) pattern of the Gd2O3 films showed that they had a poly-crystalline structure. The dielectric constants of Gd2O3 films oxidized at 30 and 60 V are 9.4 and 12.2, respectively. The equivalent oxide thickness (EOT) of the Gd2O3 stacked oxide is in the range of 5.8–9.4 nm. The MOS capacitor with Gd2O3 exhibits interesting electrical properties. Longer oxidation time reduced the leakage current density for 30 V anodic oxidation but increased the leakage current density for 60 V anodic oxidation. This work reveals that Gd2O3 could also be an alternative dielectric for Si substrate and therefore, might pave the way to fabricate CMOS devices in the future.
Keywords: Gadolinium oxide; Anodic oxidation; Dielectric constant; Equivalent oxide thickness;
Mechanical properties of sol–gel derived lead zirconate titanate thin films by nanoindentation by Huaping Wu; Linzhi Wu; Qiu Sun; Weidong Fei; Shanyi Du (5492-5496).
Lead zirconate titanate (PZT) thin films are deposited on platinized silicon substrate by sol–gel process. The crystal structure and surface morphology of PZT thin films are characterized by X-ray diffraction and atomic force microscopy. Depth-sensing nanoindentation system is used to measure mechanical characteristics of PZT thin films. X-ray diffraction analyses confirm the single-phase perovskite structures of all PZT thin films. Nanoindentation measurements reveal that the indentation modulus and hardness of PZT thin films are related with the grain size and crystalline orientation. The increases of the indentation modulus and hardness with grain size are observed, indicating the reverse Hall–Petch effect. Furthermore, the indentation modulus of (1 1 1)-oriented PZT thin film is higher than those of (1 0 0)- and random-oriented films. The consistency between experimental data and numerical results of the effective indentation moduli for fiber-textured PZT thin films using Voigt–Reuss–Hill model is obtained.
Keywords: Lead zirconate titanate film; Nanoindentation; Indentation modulus; Hardness; Crystalline orientation;
Wettability characteristic of PTFE and glass surface irradiated by keV ions by Yan Chen; Ziqiang Zhao; Yingmin Liu (5497-5500).
Commercial PTFE and soda lime glass were irradiated by keV O3+ and F4+. After irradiation, in contrast to the decrease of contact angle on PTFE, contact angle on glass increased apparently. SEM observation revealed that irradiation did not cause noticeable change in surface topological structure. XPS was used to investigate chemical structure changes on the surface. Defluorination effect and formation of oxygen containing group caused by irradiation were considered to the reason of more hydrophilic PTFE surface. On the surface of irradiated glass, more carbon contaminations were observed. The differences of underlying physical and chemical processes between the two kinds of samples are discussed.
Keywords: Wettability; PTFE; Glass; Ion irradiation; XPS; SEM;
Surface functionalization, morphology and thermal properties of polyamide6/O-MMT composite nanofibers by Fe2O3 sputter coating by Yibing Cai; Fenglin Huang; Qufu Wei; Enci Wu; Weidong Gao (5501-5505).
In the present work, the pure polyamide6 (PA6) nanofiber and PA6/organically modified montmorillonite (O-MMT) composite nanofiber were firstly prepared by a facile compounding process with electrospinning, and then coated by nanosize Fe2O3 using magnetron sputter technique. The effects of Fe2O3 sputter coating on structures, surface morphology and thermal stability were characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), atomic force microscope (AFM) and thermogravimetric analyses (TGA), respectively. The SEM images showed that the diameters of composite nanofiber were decreased with the loadings of O-MMT and the nanosize Fe2O3 is well coated on the surface of the homogeneous and cylindrical nanofibers. The XPS spectra reflected the chemical features of the deposited nanostructures. The EDX confirmed the presence of the O-MMT and Fe2O3 in the fibers. The AFM observation revealed that there was a remarkable difference in the surface morphology of composite nanofiber before and after sputter coating. The TGA analysis indicated the barrier effects of silicate clay layers and catalysis effects of Fe2O3 improved thermal stability properties of the composite nanofiber.
Keywords: Electrospinning; Sputter coating; PA6/O-MMT composite nanofibers; Surface morphology; Thermal stability;
Self-assembled film thickness determination by focused ion beam by J. Dejeu; R. Salut; M. Spajer; F. Membrey; A. Foissy; D. Charraut (5506-5510).
The thickness evolution of multilayer film is investigated by focused ion beam (FIB) in the domain of polymer multilayers. This method, currently used in the modification and the characterization of integrated circuits, proves it is possible to determine the polymer film thickness. Sample cutting and its observation of the cross-section are performed in the FIB without leaving the vacuum chamber. Two main conclusions can be drawn: (1) the roughness of the film increases with the number of layer deposit, (2) the film growth changes from nonlinear (called exponential) to linear beyond 300 nm (70 layers).
Keywords: Multilayer; Polyelectrolytes; Thin film characterization; Focused ion Beam;
Exciplex or electroplex emissions from the interface between aromatic diamine and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline? by Haina Zhu; Zheng Xu; Fujun Zhang; Suling Zhao; Dandan Song (5511-5513).
Organic light-emitting diodes (OLEDs) have been fabricated which consist of N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine) (TPD), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), and tris(8-hydroxyquinoline) aluminum (Alq3). Four emission peaks located at about 401 nm, 425 nm, 452 nm and 480 nm have been obtained in the electroluminescence (EL) spectra of these devices. The former two emissions originate from the exciton emission of TPD molecular. The last two emissions could be attributed to local (LOC) exiplex emission and charge transfer (CT) exiplex emission at the interface between TPD and BCP layers, respectively.
Keywords: Exciplex emission; Electroplex emission; Electroluminescence; Interface;
Influence of zinc ion implantation on surface nanomechanical performance and corrosion resistance of biomedical magnesium–calcium alloys by Y.Z. Wan; G.Y. Xiong; H.L. Luo; F. He; Y. Huang; Y.L. Wang (5514-5516).
It is believed that magnesium and its alloys may find applications in biomedical fields as implants, bone fixation devices, and tissue engineering scaffolds. However, their corrosion rate must be controlled. In this study, biomedical magnesium–calcium (Mg–Ca) alloys were ion-implanted with zinc. The surface nanomechanical performance and corrosion behavior of the ion-implanted Mg–Ca alloys are determined. The results show that zinc ion implantation at a dose of 0.9 × 1017 ions/cm2 significantly improves the surface hardness and modulus. However, the results on corrosion resistance reveal that zinc ion implantation degrades the corrosion behavior of Mg–Ca alloys. Thus, zinc is not a favorable element for the ion implantation treatment of biomedical Mg–Ca alloys.
Keywords: Magnesium alloys; Ion implantation; Nanomechanical properties; Corrosion behavior;
Effect of texture dispersion on the effective biaxial modulus of cubic polycrystalline films by Huaping Wu; Linzhi Wu; Qilin He; Peiwei Zhang; Shanyi Du (5517-5523).
The effective biaxial modulus of fiber-textured cubic polycrystalline films with texture dispersion is estimated using Voigt–Reuss–Hill and Vook–Witt grain-interaction models. The orientation distribution function with Gaussian distributions of two Euler angles θ and ϕ is adopted to analyze the effect of texture dispersion degree on the effective biaxial modulus. Numerical results based on Cu and Cr fiber-textured films show that the distribution of angle ϕ has slight influence on the effective biaxial modulus of (0 0 1)-fiber-textured films if and only if the distribution of out-of-plane angle θ is narrow. Enhanced θ and ϕ distributions destroy the perfect fiber textures and as a result the films represent an evolution of ideal (h k l) fiber textures to nonideal or random textures with varying full widths at half maximums of θ and ϕ.
Keywords: Effective biaxial modulus; Texture dispersion; Fiber texture; Cubic polycrystalline films;
Optimisation of direct laser structuring of printed circuit boards by Robert Rozman; Blaž Kmetec; Boštjan Podobnik; Drago Kovačič; Edvard Govekar (5524-5529).
A model-based optimisation of the process of printed circuit board laser structuring is presented. For this purpose, a comprehensive theoretical model of the interaction between the travelling pulsed laser beam and conductive layer, as well as between the laser beam and the induced plasma plume is employed. The model is used to calculate process speed. Based on the process speed determined, the influence of pulse power, duration, and frequency on process speed is analysed. In addition, an optimal range of process parameters with respect to process speed and quality is defined.
Keywords: Laser structuring; Modelling; Plasma; Power scaling; Pulse duration scaling;
Adsorption of 1,2-diaminoethane on ZnO thin films from p-xylene by Jolanta Światowska-Mrowiecka; Sandrine Zanna; Kevin Ogle; Philippe Marcus (5530-5539).
The interaction of 1,2-diaminoethane (DAE) with ZnO thin films prepared by electrodeposition and magnetron sputtering was investigated by X-ray photoelectron spectroscopy (XPS). The samples were exposed to organic solution of 0.5 M DAE–p-xylene in an Ar atmosphere glove box (O2 and H2O <5 ppm), directly connected to the XPS analysis chamber by an anaerobic and anhydrous transfer system. A clear interaction of DAE with the ZnO surface is evidenced by the presence of a high intensity N1s peak at BE = 399.5 ± 0.2 eV and C1s at BE = 286.3 ± 0.2 eV which are attributed to C–N bonding. The atomic ratio C:N was very close to 1:1 consistent with the molecular, non-dissociative adsorption of DAE on the ZnO layer. No significant difference in adsorption of DAE was observed for three different ZnO surfaces despite slight differences in their acid/base properties as evidenced by the O/OH ratio. The results are interpreted in terms of adsorption on Brönsted acid sites. A uniform layer model was used to approximate the DAE film thickness, which was found to be around 10 Å on three studied samples. The N1s and C1sB signals were observed to decrease on sample exposure to vacuum and/or X-ray irradiation and additional N1sB peak appeared at lower binding energy at around 398.5 ± 0.2 eV. This is interpreted by the desorption and modification of DAE, indicating low stability of the adsorbed state on ZnO. The exposure to water of the sample with adsorbed DAE causes a significant decrease of the N1sA and C1sB peak intensities attributed to the adsorbed DAE molecule, demonstrating the instability of the DAE–ZnO interface in water.
Keywords: 1,2-Diaminoethane (DAE); Xylene; Zinc oxide; Acid/base properties; XPS;
Preparation of cobalt oxide thin films and its use in supercapacitor application by S.G. Kandalkar; J.L. Gunjakar; C.D. Lokhande (5540-5544).
Present work explored a room temperature, simple and low cost chemical route for the cobalt oxide film onto copper substrate from cobalt chloride (CoCl2·6H2O) precursor and characterization for its structural and electrochemical properties for supercapacitor application. The morphology and crystal structure of the film were investigated by scanning electron microscopy and X-ray diffraction techniques, respectively. The electrochemical supercapacitive properties of cobalt oxide film were evaluated using cyclic voltammetry and galvanostatic charge–discharge methods. The film showed maximum specific capacitance of (165 F/g) in 1.0 M aqueous KOH electrolyte at scan rate 10 mV/s.
Keywords: Cobalt oxide; Thin films; Cyclic voltammetry; Supercapacitor; Charge–discharge;
Synthesis and characterization of TiO2 nanotubes for humidity sensing by Yanyan Zhang; Wuyou Fu; Haibin Yang; Qi Qi; Yi Zeng; Tong Zhang; Ruixia Ge; Guangtian Zou (5545-5547).
The highly ordered TiO2 thin films are prepared by anodic oxidation and calcined at 300, 400, 500 and 600 °C, respectively. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) are employed to analyze the structure and the morphology of the TiO2 films. We design a novel sensor to investigate the humidity sensing behaviours of the samples. The samples calcined at 600 °C show high sensitivity with nearly two orders change in the resistance and short response and recovery time (<190 s) during the relative humidity variation from 11 to 95%.
Keywords: Titania nanotubes; Anodization; Humidity sensor; Thin film; Nanostructure;
Effect of feedstock powder characteristics on microstructure and mechanical properties of lanthanum silicate coatings deposited by atmospheric plasma spraying by Wei Gao; Hanlin Liao; Christian Coddet (5548-5551).
Lanthanum silicate coatings were deposited onto stainless steel substrates by atmospheric plasma spraying (APS) using mechanically mixed (type A) and calcined feedstock (type B) powders. The phase composition, microstructure, density and porosity of coatings prepared from the two types of powder were compared.
Keywords: La10(SiO4)6O3; Electrolyte; Plasma spraying; Microhardness;
Structural study of thin films prepared from tungstate glass matrix by Raman and X-ray absorption spectroscopy by Bianca Montanari; Anne J. Barbosa; Sidney J.L. Ribeiro; Younes Messaddeq; Gaël Poirier; Máximo S. Li (5552-5556).
Thin films were prepared using glass precursors obtained in the ternary system NaPO3 ―BaF2 ―WO3 and the binary system NaPO3 ―WO3 with high concentrations of WO3 (above 40% molar). Vitreous samples have been used as a target to prepare thin films. Such films were deposited using the electron beam evaporation method onto soda-lime glass substrates. Several structural characterizations were performed by Raman spectroscopy and X-ray Absorption Near Edge Spectroscopy (XANES) at the tungsten LI and LIII absorption edges. XANES investigations showed that tungsten atoms are only sixfold coordinated (octahedral WO6) and that these films are free of tungstate tetrahedral units (WO4). In addition, Raman spectroscopy allowed identifying a break in the linear phosphate chains as the amount of WO3 increases and the formation of P―O―W bonds in the films network indicating the intermediary behavior of WO6 octahedra in the film network. Based on XANES data, we suggested a new attribution of several Raman absorption bands which allowed identifying the presence of W―O− and W＝O terminal bonds and a progressive apparition of W―O―W bridging bonds for the most WO3 concentrated samples (above 40% molar) attributed to the formation of WO6 clusters.
Keywords: Glass; Tungsten; Thin film;
Grazing-incidence small-angle X-ray scattering from alkaline phosphatase immobilized in atmospheric plasmapolymer coatings by M.G. Ortore; R. Sinibaldi; P. Heyse; S. Paulussen; S. Bernstorff; B. Sels; P. Mariani; F. Rustichelli; F. Spinozzi (5557-5563).
Grazing-incidence small-angle X-ray scattering (GISAXS) has been used to study proteins embedded in thin polymer films obtained by a new cold, atmospheric-pressure plasma technique. In order to test the efficiency of the technology, four samples of alkaline phosphatase incorporated in organic polymer coatings in different plasma conditions have been investigated. Data have been analysed in the framework of the distorted-wave Born approximation (DWBA), by using a new method for the simultaneous fitting of the two-dimensional diffuse scattering from each sample. As a result, protein film concentration and aggregation state as well as a set of parameters describing the polymer coatings have been obtained.
Keywords: GISAXS; Polymer coatings; Proteins; Atmospheric-pressure plasma deposition;
Comparison and semiconductor properties of nitrogen doped carbon thin films grown by different techniques by F. Alibart; O. Durand Drouhin; M. Benlahsen; S. Muhl; S. Elizabeth Rodil; E. Camps; L. Escobar-Alarcon (5564-5568).
Amorphous carbon nitride (a-CN x ) thin films have been synthesised by three different deposition techniques in an Ar/N2 gas mixture and have been deposited by varying the percentage of nitrogen gas in the mixture (i.e. the N2/Ar + N2 ratio) from 0 to 10%. The variation of the electrical conductivity and the gap values of the deposited films versus the N2/Ar + N2 ratio were investigated in relation with their local microstructure. Film composition was analysed using Raman spectroscopy and optical transmission experiments. The observed variation of electrical conductivity and optical properties are attributed to the changes in the atomic bonding structures, which were induced by N incorporation, increasing both the sp2 carbon content and their relative disorder. The low N content samples seem to be an interesting material to produce films with interesting properties for optoelectronic applications considering the facility to control the gas composition as a key parameter.
Keywords: Carbon nitride; DC sputtering; Radio frequency magnetron sputtering; Pulsed laser deposition;
An electroactive co-polymer as corrosion inhibitor for steel in sulphuric acid medium by Ganesha Achary; Y. Arthoba Naik; S. Vijay Kumar; T.V. Venkatesha; B.S. Sherigara (5569-5573).
The corrosion behavior of mild steel in sulphuric acid solution containing various concentrations of a co-polymer formed between maleic anhydride and N-vinyl-2-pyrrolidone (VPMA) was investigated using weight-loss, polarization and electrochemical impedance techniques. The polymer acts as an effective corrosion inhibitor for steel in sulphuric acid medium. The inhibition process is attributed to the formation of an adsorbed film of co-polymer on the metal surface which protects the metal against corrosion. Scanning electron microscopy (SEM) studies of the metal surfaces confirmed the existence of an adsorbed film. The adsorption followed the Langmuir isotherm. The protection efficiency increased with increase in inhibitor concentration and decreased with increase in temperature and acid concentration. The thermodynamic functions of the adsorption and dissolution processes were evaluated.
Keywords: Adsorption; Corrosion inhibition; Co-polymer and electroactive;
Synergism between rare earth cerium(IV) ion and vanillin on the corrosion of steel in H2SO4 solution: Weight loss, electrochemical, UV–vis, FTIR, XPS, and AFM approaches by Xianghong Li; Shuduan Deng; Hui Fu; Guannan Mu; Ning Zhao (5574-5586).
The synergism between rare earth cerium(IV) ion and vanillin (4-hydroxy-3-methoxy-benzaldehyde) on the corrosion of cold rolled steel (CRS) in 1.0 M H2SO4 solution at five temperatures ranging from 20 to 60 °C was first studied by weight loss and potentiodynamic polarization methods. The inhibited solutions were analyzed by ultraviolet and visible spectrophotometer (UV–vis). The adsorbed film of CRS surface containing optimum doses of the blends Ce4+–vanillin was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). The results revealed that vanillin had a moderate inhibitive effect, and the inhibition efficiency (IE) increased with the vanillin concentration. The adsorption of vanillin obeyed Temkin adsorption isotherm. Polarization curves showed that vanillin was a mixed-type inhibitor in sulfuric acid, while prominently inhibited the cathodic reaction. For the cerium(IV) ion, it had a negligible effect, and the maximum IE was only about 20%. However, incorporation of Ce4+ with vanillin improved significantly the inhibition performance. The IE for Ce4+ in combination with vanillin was higher than the summation of IE for single Ce4+ and single vanillin, which was synergism in nature. A high inhibition efficiency, 98% was obtained by a mixture of 25–200 mg l−1 vanillin and 300–475 mg l−1 Ce4+. UV–vis showed that the new complex of Ce4+–vanillin was formed in 1.0 M H2SO4 for Ce4+ combination with vanillin. Polarization studies showed that the complex of Ce4+–vanillin acted as a mixed-type inhibitor, which drastically inhibits both anodic and cathodic reactions. FTIR and XPS revealed that a protective film formed in the presence of both vanillin and Ce4+ was composed of cerium oxide and the complex of Ce4+–vanillin. The synergism between Ce4+ and vanillin could also be evidenced by AFM images. Depending on the results, the synergism mechanism was discussed from the viewpoint of adsorption theory.
Keywords: Cold rolled steel; Sulfuric acid; Vanillin; Rare earth; Cerium(IV) ion; UV–vis; FTIR; XPS; AFM; Corrosion inhibitor; Adsorption; Synergism;
The cleavage of the methane C―H bond over PdO/H-BEA: A density functional theory study by Yun-xiang Pan; Chang-jun Liu; Peng Shi (5587-5593).
Cluster models were used to represent the β-type cationic sites of the protonated beta zeolite (H-BEA) and the loading of PdO on these sites. The properties of these clusters and the cleavage of methane C―H bond over these clusters were studied using density functional theory (DFT) method. The stability of H-BEA was enhanced due to the formation of hydrogen bonds. After PdO loading, the Pd atom bonds to four oxygen atoms among which three H-BEA framework oxygen atoms are included to form an approximate planar structure with Pd in the centre. This structure is very similar to that of bulk PdO. The acidic proton of H-BEA and the oxygen atom of PdO participate in the cleavage of methane C―H bond, indicating that PdO is the active species for the activation of methane. Over the clusters constructed in the present work, the calculated energy barriers for the cleavage of methane C―H bond are in the region between 17.54 and 21.02 kcal mol−1.
Keywords: Zeolite; Palladium; Methane; C―H bond cleavage; Cluster model; Density functional theory;
Effect of humidity on domain switching behaviors of BaTiO3 single crystal under sustained load by B. Jiang; Y. Bai; W.Y. Chu; S.Q. Shi; L.J. Qiao; Y.J. Su (5594-5598).
Domain switching behaviors of BaTiO3 single crystal in humidity conditions were studied by polarized light microscopy (PLM) and atomic force microscopy (AFM). The results showed that the low humidity has no effect on both a–b domain configuration and a–c domain configuration under sustained load. However, the high humidity can promote a domain switching to c domain under sustained load. The difference of energy reduction induced by H2O molecules between c domains and a(b) domains leads to this phenomenon.
Keywords: Domain switching; Humidity; BaTiO3 single crystal; Sustained load;
Fabrication of superhydrophobic surfaces on aluminum by Hui Wang; Dan Dai; Xuedong Wu (5599-5601).
A superhydrophobic surface was prepared on aluminum substrate. Anodization and low-temperature plasma treatment were used to create micro–nano-structure and subsequently trichlorooctadecyl-silane modified the rough surface. The result shows that the water static contact of the aluminum surface after anodization and modification by trichlorooctadecyl-silane reaches to 152.1°. A rougher surface with some micro–nano-pores and small mastoids along the edges of pores was generated when low-temperature plasma treatment was applied to anodized aluminum film, resulting in water static contact angle up to 157.8°.
Keywords: Superhydrophobic surface; Anodization; Aluminum; Low-temperature plasma treatment;
Characteristics of Si-doped Sb2Te3 thin films for phase-change random access memory by Yin Zhang; Jie Feng; Zufa Zhang; Bingchu Cai; Yinyin Lin; Ting’ao Tang; Bomy Chen (5602-5606).
The characteristics of Si-doped Sb2Te3 thin films were investigated using differential scanning calorimetry (DSC), four-point probe technique, X-ray diffraction (XRD) analysis and high resolution transmission electron microscopy (HRTEM). It is found that the as-deposited Sb2Te3 film in our study is partly crystallized. Silicon doping increases the crystallization temperature and resistivity of Sb2Te3 film significantly. XRD and HRTEM analyses indicated that some of the doped Si atoms substitute for Sb or Te in the lattice, while others exists at the grain boundaries in the form of amorphous phase, which may be responsible for grain size reduction and high crystalline resistivity of Si-doped specimens. Compared with the conventional Ge2Sb2Te5 film, Si-doped Sb2Te3 films exhibit lower melting temperature and higher crystalline resistivity, which is beneficial to RESET current reduction of phase-change random access memory (PRAM). These results show the feasibility of Si-doped Sb2Te3 films in PRAM application.
Keywords: Sb2Te3; Silicon doping; Melting temperature; Resistivity; RESET current; PRAM;
Formation of Au nano-patterns on various substrates using simplified nano-transfer printing method by Jong-Woo Kim; Ki-Yeon Yang; Sung-Hoon Hong; Heon Lee (5607-5611).
For future device applications, fabrication of the metal nano-patterns on various substrates, such as Si wafer, non-planar glass lens and flexible plastic films become important. Among various nano-patterning technologies, nano-transfer print method is one of the simplest techniques to fabricate metal nano-patterns. In nano-transfer printing process, thin Au layer is deposited on flexible PDMS mold, containing surface protrusion patterns, and the Au layer is transferred from PDMS mold to various substrates due to the difference of bonding strength of Au layer to PDMS mold and to the substrate. For effective transfer of Au layer, self-assembled monolayer, which has strong bonding to Au, is deposited on the substrate as a glue layer.In this study, complicated SAM layer coating process was replaced to simple UV/ozone treatment, which can activates the surface and form the –OH radicals. Using simple UV/ozone treatments on both Au and substrate, Au nano-pattern can be successfully transferred to as large as 6 in. diameter Si wafer, without SAM coating process. High fidelity transfer of Au nano-patterns to non-planar glass lens and flexible PET film was also demonstrated.
Keywords: Nano-transfer print method; Large area patterning; Au nano-pattern; UV/ozone treatment; Self-assembled monolayer (SAM) coating; Non-planar glass lens; Flexible PET film;
Electrodeposition and characterization of thin selenium films modified with lead ad-atoms by Murilo F. Cabral; Hugo B. Suffredini; Valber A. Pedrosa; Sonia T. Tanimoto; Sergio A.S. Machado (5612-5617).
The deposition and characterization of Se films doped with Pb underpotentially deposited (UPD) ad-atoms was studied in this work. The employed experimental techniques were cyclic voltammetry, chronoamperometry, electrochemical impedance spectroscopy, UV–vis spectroscopy and atomic force microscopy. The initial deposition of Se film by chronoamperometry yielded a thin film composed of approximately 700 layers. The Pb UPD on Se was achieved by chronoamperometry in a potential value previously determined in voltammetric experiments. This deposition yielded a deposition charge of approximately 7.5% of the total one. The film resistance altered from 320 Ω cm−2 for Se to 65 Ω cm−2 for the Se/Pb one. Flat band potential values and number of acceptors and donors were also calculated for both films and the values obtained were +0.95 and −0.51 V for Se and Se/Pb, respectively. The Se coating presented 1.2 × 1017 cm−3 acceptors while the Se/Pb one presented 3.2 × 1017 cm−3 donors. The band gap values for both films were 2.4 eV and 1.9 eV, correspondingly.
Keywords: Selenium; Semiconductor films; UPD; Band gap; Flat band potential; Donors; Acceptors; Se/Pb films;
Corrosion behavior and protective ability of Zn and Zn–Co electrodeposits with embedded polymeric nanoparticles by N. Boshkov; N. Tsvetkova; P. Petrov; D. Koleva; K. Petrov; G. Avdeev; Ch. Tsvetanov; G. Raichevsky; R. Raicheff (5618-5625).
The anodic behavior, corrosion resistance and protective ability of Zn and alloyed Zn–Co (∼3 wt.%) nanocomposite coatings were investigated in a model corrosion medium of 5% NaCl solution. The metallic matrix of the layers incorporates core–shell nano-sized stabilized polymeric micelles (SPMs) obtained from poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) block co-polymers. The protective properties of the composite coatings were evaluated using potentiodynamic polarization technique, polarization resistance measurements and powder X-ray diffraction. The sizes and distribution of the stabilized polymeric micelles in the starting electrolytes used as well as in the metal matrices of the layers were investigated using scanning and transmission electron microscopy. The results obtained are compared to those of electrodeposited Zn and Zn–Co (∼3 wt.%) alloy coatings at identical conditions and demonstrate the enhanced protective characteristics of the Zn nanocomposites during the investigating period. The influence of the SPMs on the corrosion resistance of the nanocomposite layers is commented and discussed.
Keywords: Corrosion; Stabilized polymeric micelles; X-ray diffraction; Zinc; Zinc alloy;
Bubble creation and collapse during excimer laser ablation of weak absorbing polymers by T. Efthimiopoulos; H. Kiagias; S. Christoulakis; N. Merlemis (5626-5630).
We present evidence suggesting that XeCl laser ablation of a weakly absorbing poly-methyl-methacrylate (PMMA) polymer, done by chemical, thermal bond breaking of the polymer chain or optical breakdown of the material, which involves plasma generation, creates a cloud of small asymmetric near the surface bubbles, which subsequently expand and aggregate during the same laser pulse duration or in subsequent pulses depending on the laser pulse energy. When a critical volume is reached each bubble collapses in a high pressure and temperature central point and rebounds ejecting a hot jet of material on the non-irradiated area of the polymer and creating craters on the surface. A characteristic bipolar pressure wave corresponding to the bubble collapse, explosion and rebound is observed. The number density of the craters on the surface is a function of the laser pulse sequence number and the laser pulse energy density.
Keywords: PMMA; Laser ablation; Bubble dynamics;
Study of Ni/Si(1 0 0) solid-state reaction with Al addition by Yi-Fei Huang; Yu-Long Jiang; Guo-Ping Ru; Bing-Zong Li (5631-5634).
The characteristics of Ni/Si(1 0 0) solid-state reaction with Al addition (Ni/Al/Si(1 0 0), Ni/Al/Ni/Si(1 0 0) and Al/Ni/Si(1 0 0)) is studied. Ni and Al films were deposited on Si(1 0 0) substrate by ion beam sputtering. The solid-state reaction between metal films and Si was performed by rapid thermal annealing. The sheet resistance of the formed silicide film was measured by four-point probe method. The X-ray diffraction (XRD) was employed to detect the phases in the silicide film. The Auger electron spectroscopy was applied to reveal the element profiles in depth. The influence of Al addition on the Schottky barrier heights of the formed silicide/Si diodes was investigated by current–voltage measurements. The experimental results show that NiSi forms even with the addition of Al, although the formation temperature correspondingly changes. It is revealed that Ni silicidation is accompanied with Al diffusion in Ni film toward the film top surface and Al is the dominant diffusion species in Ni/Al system. However, no Ni x Al y phase is detected in the films and no significant Schottky barrier height modulation by the addition of Al is observed.
Keywords: Ni-silicide; Al addition; Schottky barrier height;
β-Phase of poly(vinylidene fluoride) formation in poly(vinylidene fluoride)/poly(methyl methacrylate) blend from solutions by Wenzhong Ma; Jun Zhang; Shuangjun Chen; Xiaolin Wang (5635-5642).
The effect of single and mixed solvent on the crystallization behavior of the PVDF/PMMA blend from solutions was investigated. The films cast from the good solvent N,N-dimethylformamide (DMF) dominantly yielded the β-phase crystal with the highest crystallinity of PVDF. Those deposited from the methyl ethyl ketone (MEK) and tetrahydrofuran (THF) exhibited a mixture of α- and some extra β-phase crystals and presented the low crystallinity of PVDF. The crystallization behavior and morphology of the films cast from the mixed solvent (THF/DMF) revealed an enormous dependence on the DMF content. The increased DMF content in the mixed solvent enhanced the interactions between polymers and solvents, and favored the β-crystal of PVDF formation but hindered the α-phase of PVDF formation. Thus, the total crystallinity of PVDF in the blend film was decreased with the DMF content increasing, because of the decreased α-phase of PVDF. In addition, the morphological feature revealed that the voids between the PVDF spherulites were eliminated remarkably by blending with PMMA. The average size of the connected spherulite on top surface of the film can grow into larger as DMF content increased.
Keywords: Poly(vinylidene fluoride) (PVDF); Crystallization; Film; Solution;
Catalytic activity of Fe, Co and Fe-Co-MCM-41 for the growth of carbon nanotubes by chemical vapour deposition method by T. Somanathan; A. Pandurangan (5643-5647).
Iron, cobalt and a mixture of iron and cobalt incorporated mesoporous MCM-41 molecular sieves were synthesised by hydrothermal method and used to investigate the rules governing their nanotube producing activity. The catalysts were characterised by XRD and N2 sorption studies. The effect of the catalysts has been investigated for the production of carbon nanotubes at an optimised temperature 750 °C with flow rate of N2 and C2H2 is 140 and 60 ml/min, respectively for a reaction time 10 min. Fe-Co-MCM-41 catalyst was selective for carbon nanotubes with low amount of amorphous carbon with increase in single-walled carbon nanotubes (SWNTs) yield at 750 °C. Formation of nanotubes was studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Transmission electron microscope and Raman spectrum was used to follow the quality and nature of carbon nanotubes formed and the graphitic layers and disordered band, which shows the clear evidence for the formation of SWNTs, respectively. The result propose that the diameter of the nanotubes in the range of 0.78–1.35 nm. Using our optimised conditions for this system, Fe-Co-MCM-41 showed the best results for selective SWNTs with high yield when compared with Fe-MCM-41 and Co-MCM-41.
Keywords: Carbon nanotubes; Chemical vapour deposition; Catalytic processes; Transmission electron microscopy;
Erratum to “Catalysis of dispersed silver particles on directional etching of silicon” [Appl. Surf. Sci. 254(10) (2008) 3061–3066] by Y.M. Yang; Paul K. Chu; Z.W. Wu; S.H. Pu; T.F. Hung; K.F. Huo; G.X. Qian; W.J. Zhang; X.L. Wu (5648).