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Applied Surface Science (v.254, #9)

Fabrication of superhydrophobic surfaces with poly(furfuryl alcohol)/multi-walled carbon nanotubes composites by Xue-Hu Men; Zhao-Zhu Zhang; Hao-Jie Song; Kun Wang; Wei Jiang (pp. 2563-2568).

Superhydrophobic films of poly(furfuryl alcohol)/multi-walled carbon nanotubes (PFA/MWNTs) composites have been obtained by using fluorocarbon-modified MWNTs (MWNT-OOCC₇F₁₅), PFA, and PTFE with a simple preparation method. The prepared films showed both high contact angle and small sliding angle for water droplets. The chemical compositions and microstructures of the resultant film surfaces were also investigated by means of infrared spectroscopy, X-ray photoelectron spectroscopy, and field emission scanning electron microscope, respectively. Both the formed multiscale roughness structures and the lower surface energy play an important role in creating the superhydrophobic surfaces of PFA/MWNTs composites.

Keywords: Superhydrophobic surfaces; PFA/MWNTs composites; Chemical modification; Multiscale roughness structures

Effect of surface species on Cu-TiO₂ photocatalytic activity by Baifu Xin; Peng Wang; Dandan Ding; Jia Liu; Zhiyu Ren; Honggang Fu (pp. 2569-2574).

The Cu-TiO₂ nanoparticles with different Cu dopant content were prepared by sol–gel method. The structure of the as-prepared catalysts and the surface species of Cu-TiO₂ were determined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and diffuse reflection spectroscopy (DRS). The relationship between the photocatalytic activity and the surface species of Cu-TiO₂ was revealed via the measurement of surface photovoltage spectroscopy (SPS) as well as the degradation of the rhodamine B (RhB). The experimental results suggest that the Cu-TiO₂ photocatalysts with appropriate content of Cu (about 0.06mol%) possess abundant electronic trap, which effectively inhibits the recombination of photoinduced charge carriers, improving the photocatalytic activity of TiO₂. While at high Cu dopant region (>0.06mol%), the excessive oxygen vacancies and Cu species can become the recombination centers of photoinduced electrons and holes. Meanwhile, at heavy Cu doping concentration, excessive P-type Cu₂O can cover the surface of TiO₂, which leads to decrease in the photocatalytic activity of photocatalyst. The photocatalytic experimental results are in good agreement with the conclusions of SPS measurements, indicating that there is a close relationship between the photocatalytic activity and the intensity of SPS spectra.

Keywords: TiO; ₂; Cu doping; Photocatalysis; SPS

Synthesis and characterization of Co (Ni or Cu)-MCM-41 mesoporous molecular sieves with different amount of metal obtained by using microwave irradiation method by Tingshun Jiang; Qian Zhao; Kangmin Chen; Yajing Tang; Longbao Yu; Hengbo Yin (pp. 2575-2580).

Co (Ni or Cu)-MCM-41 mesoporous molecular sieves with different amount of metal were synthesized by using cetyltrimethyl ammonium bromide as a template and by a novel microwave irradiation method. These samples were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and N₂ physical adsorption. The experimental results show that Co (Ni or Cu)-MCM-41 mesoporous molecular sieves were successfully synthesized. When the as-synthesized samples were calcined at 550°C for 10h, the template was effectively removed. Under microwave irradiation condition, Co-MCM-41 mesoporous molecular sieves have specific surface areas in a range of 745.7–1188.8m²/g and average pore sizes in a range of 2.46–2.75nm; Ni-MCM-41 mesoporous molecular sieves have specific surface areas in a range of 625.8–1161.3m²/g and average pore sizes of ca. 2.7nm; Cu-MCM-41 mesoporous molecular sieves have specific surface areas in a range of 601.6–1142.9m²/g and average pore sizes in a range of 2.46–2.76nm. On the other hand, with increasing the introduced metal amount, the specific surface area and pore volume of the synthesized Co (Ni or Cu)-MCM-41 mesoporous molecular sieves became small, and the mesoporous ordering of the samples became poor. Under the comparable synthesis conditions, the synthesized Co-MCM-41 mesoporous molecular sieve has a bigger specific surface area and a more uniform pore distribution as compared with the synthesized Ni-MCM-41and Cu-MCM-41 mesoporous molecular sieves.

Keywords: Mesoporous molecular sieve; Synthesis; Characterization; Microwave irradiation

Aggregation-based growth of silver nanowires at room temperature by Lanlan Sun; Li Wang; Yonghai Song; Cunlan Guo; Yujing Sun; Chongyang Peng; Zhelin Liu; Zhuang Li (pp. 2581-2587).

We describe an aggregation-based growth mechanism for formation of silver nanowires at room temperature. It is found that the pH of solution and the concentration ofl-cysteine capping molecules have an important effect on the formation and growth of nanowires. Characterization by atomic force microscopy (AFM) and UV–vis spectroscopy recorded as time clearly shows that the silver nanowires are grown at the expense of nanoparticles.

Keywords: PACS; 61.43.Hv; 82.80.Yc; 82.30.Nr; 61.46.Df; 82.37.GkAggregation; pH Measurement; Clusters; Nanoparticles; AFM

Surface characterisation of carbon fibre recycled using fluidised bed by G. Jiang; S.J. Pickering; G.S. Walker; K.H. Wong; C.D. Rudd (pp. 2588-2593).

X-ray photoelectron spectroscopy (XPS) was used to investigate the surface of carbon fibres recycled using a high-temperature fluidised bed. The interfacial shear strength of the recycled carbon fibres with epoxy resin was examined using a micro-droplet test. The corresponding as received carbon fibres were used as control samples. It was shown that the recycling process converted some of the surface hydroxyl groups into carbonyl and carboxylic groups due to the effect of heat in atmosphere of air. The overall O/C ratio was not changed significantly. The interfacial shear strength with epoxy resin was not affected by the change of surface oxygen composition. It was also shown that surface texture may play a dominant role in interfacial bonding performance.

Keywords: PACS; 68.35.Np; 82.65.+rCarbon fibre; XPS; Recycling; Interfacial bonding

Ultrasonic treatment of aramid fiber surface and its effect on the interface of aramid/epoxy composites by L. Liu; Y.D. Huang; Z.Q. Zhang; Z.X. Jiang; L.N. Wu (pp. 2594-2599).

Aramid fiber/epoxy composites have been treated by ultrasound during the winding process to enhance the adhesion. According to the ultrasonic treatment interlaminar shear strength (ILSS) of composites has been greatly improved. Dynamic wetting method, XPS and AFM are used to examine the microscopic properties of resultant composites. The enhanced ILSS is attributed to the ultrasonic cavitation, which improves the wetting between aramid fibers and resins.

Keywords: Ultrasound; Aramid fiber; Surface; Wettability

Preparation of well-defined polymer-silicon wafer hybrids via surface-initiated RAFT-mediated process by Liang Li; Entang Kang; Koongee Neoh (pp. 2600-2604).

A simple method was developed for the immobilization of reversible addition-fragmentation chain-transfer (RAFT) initiators on the silicon surface. Well-defined polymer-silicon hybrids, including the tethered brushes of glycidyl methacrylate (GMA) polymer, poly(ethylene glycol) monomethacrylate (PEGMA) polymer and block copolymer on a silicon wafer, were prepared via surface-initiated RAFT living radical polymerization. The “living” chain ends were used as the macroinitiator for the subsequent synthesis of diblock copolymers.

Keywords: PACS; 82.40.−g; 82.65.+rSurface-initiated RAFT; Silicon; Diblock copolymer

AlCl₃-induced crystallization of amorphous silicon thin films by Jing Qi; YangYang; Deyan He (pp. 2605-2608).

It is reported that the direct contact between Al and amorphous silicon (a-Si) enhances the crystallization of a-Si films. But the polycrystalline silicon (poly-Si) films crystallized by the direct contact of Al metal film suffer the problems of rough surface. In our study, we utilized the AlCl₃ vapor during the a-Si films deposition instead of Al metal film to enhance crystallization. X-ray diffraction (XRD) shows that the AlCl₃ vapor so successfully enhanced the crystallization of a-Si films that the crystallization was completed in 5h at 540°C. And the orientation of the poly-Si film deposited with AlCl₃ vapor is much more random than that of annealed with Al metal under layer. But the average grain size is much larger than that. Moreover, the surface of the AlCl₃-induced crystallized poly-Si film was much smoother than that of the Al-induced poly-Si film. The Al and Cl incorporation into the poly-Si film was confirmed using X-ray photoelectron spectroscopy (XPS) and found that the quantity of Al and Cl incorporated into the Si film was below the detection limit of XPS.

Keywords: PACS; 61.82.Fk; 71.20.Mq; 81.40.Ef; 81.10.−h; 68.55.−a; 81.15.−zPoly-Si thin film; Crystallization; AlCl; ₃; vapor

Selective hydrogenation of cinnamaldehyde to cinnamyl alcohol with carbon nanotubes supported Pt-Co catalysts by Yan Li; Peng-Fei Zhu; Ren-Xian Zhou (pp. 2609-2614).

The Pt-Co catalysts supported on carbon nanotubes (CNTs) have been prepared by wet impregnation and the selective hydrogenation of cinnamaldehyde (CMA) to the corresponding cinnamyl alcohol (CMO) over the catalysts has been studied in ethanol at different reaction conditions. The results show that Pt-0.17wt%Co/CNTs catalyst exhibits the highest activity and selectivity at a reaction temperature of 60°C under a pressure of around 2.5MPa, and 92.4% for the conversion of CMA and 93.6% for the selectivity of CMA to CMO, respectively. The selective hydrogenation for the CO double bond in CMA would be improved as increasing the H₂ pressure, and the selective hydrogenation for the CC double bond in CMA is enhanced as increasing the reaction temperature. In addition, these catalysts have also been characterized using transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), H₂-temperature programmed reduction (H₂-TPR) and H₂-temperature programmed desorption (H₂-TPD) techniques. The results show that Pt particles are dispersed more homogeneously on the outer surface of the nanotubes, while the strong interaction between Pt and Co would improve the increasing of activated hydrogen number because of the hydrogen spillover from reduced Pt⁰ onto CNTs and increase the catalytic activity and selectivity of CMA to CMO.

Keywords: Cinnamaldehyde (CMA); Cinnamyl alcohol (CMO); Pt-Co/CNTs catalyst; Selective hydrogenation

The influence of titanium on the properties of zinc oxide films deposited by radio frequency magnetron sputtering by Jeng-Lin Chung; Jyh-Chen Chen; Chung-Jen Tseng (pp. 2615-2620).

TiO₂-doped zinc oxide thin films were deposited on glass substrates by radio frequency (RF) magnetron sputtering with TiO₂-doped ZnO targets in an argon atmosphere. The structural properties of TiO₂-doped ZnO films doped with different TiO₂ contents were investigated. The experimental results show that polycrystalline TiO₂-doped ZnO films had the (002) preferred orientation. The deposition parameters such as the working pressure and substrate temperature of TiO₂-doped ZnO films were also investigated. The crystalline structure of the TiO₂-doped ZnO films gradually improved as the working pressure was lowered and the substrate temperature was raised. The lowest electrical resistivity for the TiO₂-doped ZnO films was obtained when the Ti addition was 1.34wt%; its value was 2.50×10⁻³Ωcm, smaller than that found in previous studies. The transmittance of the TiO₂-doped ZnO films in the visible wavelength range was more than 80%. The optical energy gap was related to the carrier concentration, and was in the range of 3.30–3.48eV.

Keywords: Resistivity; Sputtering; Zinc oxide; Optical energy gap

Measurement of optical and electrical properties of silicon microstructuring induced by ArF excimer laser at SF₆ atmosphere by M.A. Bassam; P. Parvin; B. Sajad; A. Moghimi; H. Coster (pp. 2621-2628).

The irradiation of ArF excimer laser (193nm) on Si wafer (〈111〉, n-type, arsenic-doped, 0.01Ωcm) in SF₆ atmosphere, from vacuum to 1000mbar, creates a regular self-assembled microstructure owning to a great number of microconical spikes covered with SiF₂ (fluorosilyl) layer containing sulfur impurities. The geometry of microstructure as well as the layer thickness varies with the gas pressure and the laser parameters, particularly duration, pulse energy and the dose. In this work, the electrical properties of the layer on the microstructured silicon have been investigated based on electrical impedance spectroscopy (EIS). The measured impedance significantly changes regarding to the unirradiated samples. It was shown that the corresponding electrical conductance and the dielectric constants of the layer are strongly dependent on the gas pressure and UV dose. The layer thickness was also determined in terms of SF₆ pressures.

Keywords: Silicon microstructure; Excimer laser; Electrical impedance spectroscopy (EIS) measurement; Photospectroscopy

Decomposition of thin titanium deuteride films; thermal desorption kinetics studies combined with microstructure analysis by Wojciech Lisowski; Enrico G. Keim; Zbigniew Kaszkur; Mark A. Smithers (pp. 2629-2637).

The thermal evolution of deuterium from thin titanium films, prepared under UHV conditions and deuterated in situ at room temperature, has been studied by means of thermal desorption mass spectrometry (TDMS) and a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The observed Ti film thickness dependent morphology was found to play a crucial role in the titanium deuteride (TiD_y) film formation and its decomposition at elevated temperatures. TDMS heating induced decomposition of fine-grained thin Ti films, of 10–20nm thickness, proceeds at low temperature (maximum peak temperature T_m about 500K) and its kinetics is dominated by a low energy desorption ( E_D=0.61eV) of deuterium from surface and subsurface areas of the Ti film. The origin of this process is discussed as an intermediate decomposition state towards recombinative desorption of molecular deuterium. The TiD_y bulk phase decomposition becomes dominant in the kinetics of deuterium evolution from thicker TiD_y films. The dominant TDMS peak at approx. T_m=670K, attributed to this process, is characterized by E_D=1.49eV.

Keywords: PACS; 61.72.Dd; 68.37.Hk; 68.37.Lp; 68.43.Vx; 68.55.Jk; 82.30.LpTitanium deuteride films; Thermal desorption; Microstructure; XPS

PLD of X7R for thin film capacitors by Takanori Hino; Noriyuki Matsumoto; Minoru Nishida; Takao Araki (pp. 2638-2641).

Thin film capacitors with a thickness of 200nm were prepared on SrTiO₃ (100), (110) and (111) single crystal substrates at a temperature of 973K by pulsed laser deposition (PLD) using a KrF excimer laser in an O₂–O₃ atmosphere with a gas pressure of 1Pa using an X7R sintered target. As a result, perovskite BaTiO₃ solid solution films were obtained. In the X7R thin films on (100) and (110) SrTiO₃, only diffraction peaks with strong intensities from BaTiO₃ (100) and (110), respectively, were observed. X7R films on SrTiO₃ (111) were grown epitaxially oriented to the crystal plane direction of the substrate by inserting an initial homoepitaxial SrTiO₃ layer with a thickness of 4nm. The X7R/SrTiO₃ film capacitors yielded a large volumetric efficiency of 50μF/mm³ and a temperature coefficient of capacitance (TCC) of −1.3% to 1.3% which satisfies the EIA standard specifications for X7R.

Keywords: PACS; 77.55.+fMultilayer ceramic capacitors (MLCCs); X7R; Thin films; Pulsed laser deposition

Application of laser speckle analysis for the assessment of cementitious surfaces subjected to laser cleaning by Agnieszka J. Klemm; Poologanathan Sanjeevan (pp. 2642-2649).

This paper focuses on the application of laser speckle technique for the assessment of the effectiveness of laser cleaning of cementitious surfaces. Laser speckle-based methods are non-contact, highly resolving techniques for the measurement of displacement, rotation, and strain of an illuminated area on a rough surface. Since the intensity of reflected light depends on the geometrical microstructure and colour of the samples, any alterations of the surface result in different speckle images. Analysis of speckle images presented here is based on the analysis of the distribution of intensity of reflected light obtained in a selected plane, and analysis of statistical parameters describing such distribution (skewness and kurtosis). A wide range of laser-cleaned mortar samples with different geometrical microstructure and moisture content has been subjected to the assessment by He–Ne laser. Laser speckle method has been successfully used to identify the effectiveness of the laser cleaning process with respect to different surface conditions. It appears that the changes in kurtosis and skewness should be mainly associated with the alterations of geometrical microstructure. Whereas, mean light intensity seemed to depend predominantly on the mortar's absorption characteristics (colour).

Keywords: Cementitious composite; Laser cleaning; Laser speckle analysis; Surface roughness

XPS study of five fluorinated compounds deposited on calcarenite stone by Alberto Torrisi (pp. 2650-2658).

In this work the application of XPS technique to the study of five fluorinated compounds deposited on actual calcarenite samples is presented. It has been found that the composition derived from the high-resolution XPS spectra together with the results of the C 1s fitting, allow us to derive a surface chemical formula for each of the studied compounds. These formula are in good agreement with those reported in the manufacturer data sheets if one hypothesise an arrangement of these molecules on the surface of the calcarenite stone that take into account the content of the different hydrophobic groups. In addition, the thickness of the deposited film has been calculated on the basis of the Ca and C content as well as an estimation of the coverage degree has been done. The results of this XPS study has been compared with that obtained by means of the static contact angle test.

Keywords: XPS; Protective; Calcarenite

Wettability modification of pitch-based spherical activated carbon by air oxidation and its effects on phenol adsorption by Chaojun Liu; Xiaoyi Liang; Xiaojun Liu; Qin Wang; Na Teng; Liang Zhan; Rui Zhang; Wenming Qiao; Licheng Ling (pp. 2659-2665).

The surface chemistry of pitch-based spherical activated carbon (PSAC) was modified by air oxidation to enhance its wettability as well as adsorption properties. Changes of PSAC after modification in texture, surface chemistry and wettability were studied by different techniques including N₂ adsorption, X-ray photoelectron spectroscopy (XPS) and dynamic contact angle analyzer (DCA). Phenol adsorption characteristics in different solvents on PSAC were also investigated. When PSAC was modified under an atmosphere with 20vol.% oxygen at 400 and 450°C for 5h, surface acidic groups increased from 0.11 to 1.22 and 1.60meq/g, while basic groups decreased from 0.52 to 0.03 and 0.02meq/g, respectively. After PSAC was modified, the increase of the oxygen-containing groups, especially carboxylic and phenolic ones, is responsible for the increasing of the surface acidity and the significant improvement of the wettability of PSAC. PSAC with a relatively high oxygen content provided a low adsorption capacity to phenol in aqueous solution, and the adsorption isotherms change from Langmuir class (L) to the S-shaped curve; while the solvent is changed into cyclohexane, all adsorption isotherms are type L, and the adsorption capacity to phenol increases with increasing oxygen-containing groups. Possible reasons, including the solvent effect, π– π dispersion and donor–acceptor interactions are discussed.

Keywords: Activated carbon; Functional groups; Wettability; Adsorption; Phenol

New method to calibrate binding energy using Au nanocolloids in X-ray photoelectron analysis of diamondlike carbon films with different electrical resistivities by Susumu Takabayashi; Keishi Okamoto; Kunihiko Motomitsu; Akira Terayama; Tatsuyuki Nakatani; Hiroyuki Sakaue; Hitoshi Suzuki; Takayuki Takahagi (pp. 2666-2670).

A new method to calibrate the binding energy ( E_B) using Au nanocolloids as a calibrant in XPS analysis of diamondlike carbon (DLC) is proposed by considering the DLC films with different electrical resistivities. A few microliters of a dilute aqueous solution containing Au nanocolloids were dropped onto a small local surface area of the DLC film, which became a stain before XPS measurements by gradually drying in vacuo. The observed peak E_B of the C 1s spectrum at another native surface (an area without Au nanocolloids) of the DLC film was calibrated by setting that of the Au 4f_7/2 spectrum of the Au nanocolloids to 84.0 (83.98±0.02) eV. The adequacy of this method was investigated by considering the correlation among the full width at half maximums (FWHMs) of the Au 4f_7/2 spectra of the Au nanocolloids on the DLC surfaces and that of a Au plate as a reference. Consequently, the FWHM of the Au 4f_7/2 spectrum of the Au nanocolloids on the DLC surface is a candidate to investigate the differential charging effect of the DLC surface, and the calibration method is reliable if the FWHM agrees with that of the Au plate.

Keywords: PACS; 73.61.Jc; 79.60.Bm; 79.60.Ht; 79.60.−i; 81.05.UwDiamondlike carbon (DLC); X-ray photoelectron spectroscopy (XPS); Electrical resistivity; Differential charging

A study on the wet etching behavior of AZO (ZnO:Al) transparent conducting film by Y.C. Lin; Y.C. Jian; J.H. Jiang (pp. 2671-2677).

This paper studies the wet etching behavior of AZO (ZnO:Al) transparent conducting film with tetramethylammonium hydroxide (TMAH). The optimum optoelectronic film is prepared first using designated RF power, film thickness and controlled annealing heat treatment parameters. The AZO film is then etched using TMAH etchant and AZ4620 photoresist with controlled etchant concentration and temperature to examine the etching process effect on the AZO film optoelectronic properties. The experimental results show TMAH:H₂O=2.38:97.62 under 45°C at the average etch rate of 22nm/min as the preferred parameters. The activation energy drops as the TMAH concentration rises, while the etch rate increases along with the increase in TMAH concentration and temperature. After lithography, etching and photoresist removal, the conductivity of AZO film dramatically drops from 2.4×10⁻³Ωcm to 3.0×10⁻³Ωcm, while its transmittance decreases from 89% to 83%. This is due to the poor chemical stability of AZO film against AZ4620 photoresist, leading to an increase in surface roughness. In the photoresist postbaking process, carbon atoms diffused within the AZO film produce poor crystallinity. The slight decreases in zinc and aluminum in the thin film causes a carrier concentration change, which affect the AZO film optoelectronic properties.

Keywords: AZO film; Transparent conducting film; Wet etching; Chemical stability

Synthesis of molybdenum silicide by both ion implantation and ion beam assisted deposition by Qingli Meng; Jizhong Zhang; Zhanping Li; Gaobao Li; Runbing Chen (pp. 2678-2684).

Two groups of Mo/Si films were deposited on surface of Si(100) crystal. The first group of the samples was prepared by both ion beam assisted deposition (IBAD) and metal vapor vacuum arc (MEVVA) ion implantation technologies under temperatures from 200 to 400°C. The deposited species of IBAD were Mo and Si, and different sputtering Ar ion densities were selected. The mixed Mo/Si films were implanted by Mo ion with energy of 94keV, and fluence of Mo ion was 5×10¹⁶ions/cm². The second group of the samples was prepared only by IBAD under the same test temperature range. The Mo/Si samples were analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), sheet resistance, nanohardness, and modulus of the Mo/Si films were also measured. For the Mo/Si films implanted with Mo ion, XRD results indicate that phase of the Mo/Si films prepared at 400 and 300°C was pure MoSi₂. Sheet resistance of the Mo/Si films implanted with Mo ion was less than that of the Mo/Si films prepared without ion implantation. Nanohardness and modulus of the Mo/Si films were obviously affected by test parameters.

Keywords: PACS; 68.55.Nq; 68.55.Jk; 68.60.Bs; 81.15.JjMolybdenum silicide; MEVVA; IBAD; Nanohardness

Effects of depositing temperatures on structure and optical properties of TiO₂ film deposited by ion beam assisted electron beam evaporation by Chen Yang; Huiqing Fan; Yingxue Xi; Jin Chen; Zhuo Li (pp. 2685-2689).

TiO₂, which is high in refractive index and dielectric constant, plays an important role in the fields of optics and electronics. In this work, TiO₂ films were prepared on glass substrates by the technique of ion beam assisted electron beam evaporation. The films were deposited at 50, 150 and 300°C, respectively. Then the as-deposited TiO₂ films were annealed at 450°C for 1h in vacuum atmosphere. Structures and optical properties of TiO₂ films were characterized by XRD, SEM, ellipsometry and spectrophotometer. As a result, the structure and the refractive index of films were improved by both the annealing and the increasing of the deposition temperature. The UV–vis transmittance spectra also confirmed that the deposition temperature has a significant effect on the transparency of the thin films. The highest transparency over the visible wavelength region of spectra was obtained at the deposition temperature of 300°C. The allowed direct band gap at the deposition temperature ranging from 50 to 300°C was estimated to be in the range from 3.81 to 3.92eV.

Keywords: TiO; ₂; thin films; Physical vapor deposition; Microstructure; X-ray diffraction; Optical properties

Thermal effect on superhydrophobic performance of stearic acid modified ZnO nanotowers by N. Saleema; M. Farzaneh (pp. 2690-2695).

The thermal desorption of stearic acid on superhydrophobic zinc oxide nanotowers has been investigated. The stearic acid passivated zinc oxide nanotowers provide a very high contact angle of ∼173±1.1° with a very low hysteresis of ∼1.4±0.5° due to the presence of a binary structure composed of several nanosteps on each nanotower of height ∼700nm that eventually reduces the area of contact between the drop and the nanotowers and trapping more air as revealed by the field emission scanning electron microscopy images. The superhydrophobic performance of these nanotowers, however, declines following annealing at elevated temperatures. Fourier transform infrared spectra show a reduction in the intensity of stearic acid –CH_n peaks at elevated temperatures revealing the cause of the decrease in contact angle and confirming the occurrence of thermal desorption at 184°C. The corresponding activation energy for desorption determined from our data is 0.34±0.05eV. It is found that the stearic acid has completely disappeared at 350°C, making the sample hydrophilic.

Keywords: Superhydrophobicity; ZnO nanotowers; Thermal desorption; FTIR; Contact angle; SEM

Relative roles of acetic acid, dodecyl sulfate and benzotriazole in chemical mechanical and electrochemical mechanical planarization of copper by P.C. Goonetilleke; D. Roy (pp. 2696-2707).

The efficiency of chemical mechanical or electrochemical mechanical planarization (CMP or ECMP) carried out in the fabrication of integrated circuits is largely governed by the functional chemicals used in these processes. In this work, we study the individual and combined chemical and electrochemical effects of a selected set of such chemicals that can potentially support both CMP and ECMP of copper. These chemicals include acetic acid (HAc) as a complexing agent, H2O2 as an oxidizer, and ammonium dodecyl sulfate (ADS) as a dissolution inhibitor. Surface passivating effects of ADS under both CMP (open circuit) and ECMP (voltage activated) conditions are compared with those of a standard dissolution inhibitor for Cu, benzotriazole (BTAH), and the combined effects of a BTAH–ADS mixture also are explored. The experiments are performed in the absence of mechanical polishing using static and rotating Cu disc electrodes, and electro-dissolution of Cu for ECMP is activated using a voltage pulse modulation technique. A mechanism of surface reactions is proposed to describe the relative roles of HAc, H2O2, ADS and BTAH as electrolyte components for CMP and ECMP of Cu.

Keywords: PACS; 68.08.-p; 68.43.-h; 81.20.-n; 81.65.-b; 82.45.BbCMP; Copper; Acetic acid; Surface composition; Semiconductor devices

Model study of electron beam charge compensation for positive secondary ion mass spectrometry using a positive primary ion beam by Zhengmao Zhu; Frederick A. Stevie; Dieter P. Griffis (pp. 2708-2711).

A new modeling approach has been developed to assist in the SIMS analysis of insulating samples. This approach provides information on the charging phenomena occurring when electron and positive primary ion beams impact a low conductivity material held at a high positive potential. The concept of effective leakage resistance aids in the understanding of the dynamic electrical properties of an insulating sample under dynamic analysis conditions. Modeling of steady state electron beam charge compensation involves investigation of electron injection and charge drift. Using a Monte Carlo program to simulate electron injection and dc conduction calculations to predict charge drift, detailed information regarding charging phenomena can be determined.

Keywords: Charge compensation; Electron beam; Magnetic sector; SIMS

Immobilization of bovine serum albumin on TiO₂ film via chemisorption of H₃PO₄ interface and effects on platelets adhesion by Y.J. Weng; R.X. Hou; G.C. Li; J. Wang; N. Huang; H.Q. Liu (pp. 2712-2719).

In the present study, bovine serum albumin (BSA) was successfully covalently immobilized on the surface of anatase TiO₂ film by a three-step method, i.e. application of H₃PO₄ chemisorption to increase surface –OH, which increases the amount of coupling 3-aminopropyl-triethoxylsilane (APTES), thus linking with BSA by imide bond using EDC/NHS/MES. There is no significant –OH group increase on rutile film when using the same method of phosphoric acid treatment, which suggest it is difficult for further chemical modification of the rutile film. After covalent immobilization of BSA on anatase film, an improved hemocompatibility of anti-platelet adhesion and aggregation in vitro could be recognized by LDH and SEM analysis. This study suggests BSA-immobilized anatase surface can serve as hemocompatibility material in vivo.

Keywords: Surface immobilization; TiO; ₂; film; Bovine serum albumin; Hemocompatibility

Impact of O₂ exposure on surface crystallinity of clean and Ba terminated Ge(100) surfaces by A. Cattoni; R. Bertacco; M. Cantoni; F. Ciccacci; H. Von Kaenel; G.J. Norga (pp. 2720-2724).

In analogy with the case of Sr on Si [Y. Liang, S. Gan, M. Engelhard, Appl. Phys. Lett. 79 (2001) 3591], we studied surface crystallinity and oxidation behaviour of clean and Ba terminated Ge(100) surfaces as a function of oxygen pressure and temperature. The structural and chemical changes in the Ge surface layer were monitored by LEED, XPS and real-time RHEED. In contrast to the oxidation retarding effect, observed for 1/2 monolayer of Sr on Si, the presence of a Ba termination layer leads to a pronounced increase in Ge oxidation rate with respect to clean Ge. In fact, while the Ge(100) surface terminated with 1/2ML Ba amorphizes for a pO₂ of 10⁻²Torr, LEED indicates that clean Ge forms a thin (4.5Å), 1×1 ordered oxide upon aggressive O₂ exposure (150Torr, 200°C, 30min). We briefly discuss the origins for the difference in behaviour between Ba on Ge and Sr on Si.

Keywords: Oxide epitaxy; Surface passivation; Ge; Ba; Surface termination; RHEED; XPS

Two-dimensional dopant profiling of silicon with submicron resolution using near field optics on silicon/electrolyte contacts by Mustapha Djebbouri; François Bertin; Naziha Kesri; Ahmad Bsiesy (pp. 2725-2729).

We demonstrate the possibility to use near field optics to perform two-dimensional dopant profiling on silicon surface, with deep submicron spatial resolution. The sample surface is contacted by an aqueous electrolyte giving a reverse biased junction that is illuminated by a subwavelength optical source, in near filed conditions. A staircase calibration structure was used with several boron-doped layers with either 4μm or 0.4μm thickness and doping between 10¹⁷ and 10²⁰at/cm³. Measurements were performed on the sample cross section. It is shown that photocurrent surface mapping shows up the doped areas with a lateral resolution better than 100nm.

Keywords: Optical near field microscopy; Semiconductor electrochemistry; Submicron resolution; Photocurrent mapping

Preparation of Gelatin coated hydroxyapatite nanorods and the stability of its aqueous colloidal by Minfang Chen; Junjun Tan; Yuying Lian; Debao Liu (pp. 2730-2735).

This paper describes a novel process for preparing Gelatin coated hydroxyapatite (HAp) nanorods to improve the stability of its aqueous colloid. As Gelatin is a typical protein with abundant hydroxyls, carboxys and imines, it is a very effective functional group to attach onto the surfaces of the HAp particles. Our data show that the Gelatin layer firmly coated on the hydroxyapatite nanorods, and their structure and interfacial chemical bonding have been studied using various techniques, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HRTEM), differential thermal analysis (DTA) and thermal gravimetric analysis (TGA). The reaction temperature, pH, amount of Gelatin, and Ca/P molar ratio in the material determine the quality of Gelatin coating and the stability of the HAp in aqueous solution. Moreover, an interesting phenomenon was found that the Gelatin coated HAp sediment separated by centrifugal was easily dispersed in water and forms HAp aqueous suspension. The suspension was stable for more than 24h.

Keywords: Hydroxyapatite nanorods; Gelatin coating; HAp aqueous colloid; Stability

Optical properties of sol–gel fabricated Mn/SiO₂ nanocomposites: Observation of surface plasmon resonance in Mn nanoparticles by Oleg A. Yeshchenko; Igor M. Dmitruk; Alexandr A. Alexeenko; Andriy M. Dmytruk (pp. 2736-2742).

Manganese nanoparticles were grown in silica glass and silica film on silicon substrate by annealing of the sol–gel prepared porous silicate matrices doped with manganese nitrate. Annealing of doped porous silicate matrices was performed at various conditions that allowed to obtain the nanocomposite glasses with various content of metallic Mn. TEM of Mn/SiO₂ glass indicates the bimodal size distribution of Mn nanoparticles with mean sizes of 10.5nm and 21nm. The absorption and photoluminescence spectra of Mn/SiO₂ glasses were measured. In the absorption spectra at 300nm (4.13eV) we observed the band attributed to the surface plasmon resonance in Mn nanoparticles. The spectra proved the creation of Mn²⁺ and Mn³⁺ ions in silica glass as well. The absorption spectra of Mn/SiO₂ glasses annealed in air prove the creation of manganese oxide Mn₂O₃. The measured reflection spectra of Mn/SiO₂ film manifest at 240–310nm the peculiarity attributed to surface plasmons in Mn nanoparticles.

Keywords: PACS; 73.20.Mf; 78.66.Sq; 78.67.BfNanocomposite; Manganese nanoparticles; Optical properties; Surface plasmons; Sol–gel fabrication

Effect of sol concentration on the properties of ZnO thin films prepared by sol–gel technique by M. Dutta; S. Mridha; D. Basak (pp. 2743-2747).

ZnO thin films are deposited on the glass substrates by sol–gel drain coating technique by varying the concentration of the sol. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis were used to investigate the effect of sol concentration on the crystallinity and surface morphology of the films. The results show that with increase in sol concentration, the value of full width at half maximum (FWHM) of (002) peak decreases while the strain first increases and then decreases. The sol with higher concentration results in the increase in the grain size. The studies on the optical properties show that the band gap value increases from 3.27 to 3.3eV when the sol concentration changes from 0.03 to 0.1M. The photoconductivity studies reveal that the film for 0.05M sol shows the maximum photoresponse for ultraviolet (UV) wavelength (<400nm) which is co-related with the deep-level defects. The growth and decay of the photocurrent is found to be slowest for the same film.

Keywords: ZnO; Sol–gel; Sol concentration; Optical properties; Photoconductivity

Nanostructure of thin silicon films by combining HRTEM, XRD and Raman spectroscopy measurements and the implication to the optical properties by Andreja Gajović; Davor Gracin; Igor Djerdj; Nenad Tomašić; Krunoslav Juraić; Dang Sheng Su (pp. 2748-2754).

A series of thin silicon films with different degrees of crystallinity were prepared by decomposition of silane gas highly diluted with hydrogen, in radiofrequency glow discharge. The crystallite size, shape, and the portion of crystalline phase were investigated by high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), Raman spectroscopy (RS), and X-ray powder diffraction (XRD). The absorption coefficient ( α) was calculated from the measurement of UV–vis-transmittance. By using RS, the volume fractions of the crystalline phase were estimated from the ratio of the integrated intensities of transversal optical (TO)-related crystalline and amorphous bands. These results were in excellent agreement with the mean crystallite sizes measured in HRTEM images and crystallite sizes refined from XRD measurements. The red shift of absorption, appearing as a result of the increase of the crystal fraction, depends on the size and distribution of nanocrystals.

Keywords: Silicon; Solar cells; Nanostructures; Optical properties

Passivating oxide film and growing characteristics of anodic coatings on aluminium alloys by S. Feliu Jr.; M .J. Bartolomé; J.A. González; V. López; S. Feliu (pp. 2755-2762).

The paper studies some aspects of the behaviour of four aluminium alloys under chemical etching by sodium hydroxide solution and during their subsequent anodizing in sulphuric acid solution. A correspondence is seen between etching rate, thickness of the passivating oxide film and porosity of the anodic layer. The possibility of an influence on these properties of precipitates and micro-heterogeneities in the metallic surface is suggested.

Keywords: Aluminium alloys; Passivating oxide film; Porous anodic layer; XPS

Microstructural modification by laser surface remelting and its effect on the corrosion resistance of an Al–9wt%Si casting alloy by Wislei R. Osório; Noé Cheung; José Eduardo Spinelli; Kleber S. Cruz; Amauri Garcia (pp. 2763-2770).

Aluminum alloys with silicon as a major alloying element constitute a class of materials, which provides the most significant part of all shaped castings manufactured. Such alloys have a wide range of applications in the automotive and aerospace industries. The literature presents contradictory results and no satisfactory explanations concerning to resulting microstructures provided by laser surface remelting (LSR) and its effect on the electrochemical behavior of Al–Si alloys. The aim of this study was to investigate the effect of microstructural refinement by LSR on corrosion resistance of an Al–9wt%Si casting alloy. As-cast samples were subjected to a continuous 1kW CO₂ laser. Corrosion resistance has been analyzed by an electrochemical impedance spectroscopy (EIS) technique and polarization curves carried out in both 0.5M NaCl and 0.5M H₂SO₄ solutions at 25°C. An equivalent circuit has also been proposed and impedance parameters were simulated by the ZView^® software. It was found that the structural modification provided by the LSR process induces a decreasing effect on the corrosion resistance when compared to that of the untreated sample.

Keywords: Laser surface remelting; Corrosion resistance; Electrochemical impedance; Microstructural refinement; Al–Si hypoeutectic alloys

Modeling the influence of the porosity of laser-ablated silicon films on their photoluminescence properties by M. Meunier; J.-S. Bernier; J.-P. Sylvestre; A.V. Kabashin (pp. 2771-2775).

Nanostructured porous Si-based films produced by pulsed laser ablation (PLA) from a silicon target in residual helium gas can exhibit both size-dependent (1.6–3.2eV) and fixed photoluminescent (PL) bands (1.6 and 2.2eV) with their relative contributions depending on the film porosity. We study the influence of prolonged oxidation in ambient air on properties of the fixed PL bands, associated with oxidation phenomena, and their correlation with structural properties of the films. In addition, we propose a model describing the appearance of surface radiation states for oxidized films of various porosities. Our experiments and numerical simulations led to a conclusion that the 1.6eV PL is due to a mechanism involving a recombination through the interfacial layer between Si core and an upper oxide of nanocrystals. This mechanism gives the optimal porosity of 73% for the most efficient production of 1.6eV PL centers that is in excellent agreement with our experimental results.

Keywords: PACS; 75.55.−m; 81.15.FgPulsed laser ablation; Nanostructured silicon; Visible photoluminescence; Porosity

Formation of TiN–Ir particle films using pulsed-laser deposition and their electrolytic properties in producing hypochlorous acid by H. Deno; T. Kamemoto; S. Nemoto; A. Koshio; F. Kokai (pp. 2776-2782).

Using sintered TiN and TiN–Ir (Ir contents: 5.9–14.2at.%) targets, pulsed-laser deposition (PLD) was carried out to produce thin films composed of nanoparticles and particulates in the presence of nitrogen gas. The size (2–100nm) of the produced crystalline TiN nanoparticles increased as nitrogen pressure was increased in the range from 1.33 to 1.33×10²Pa. At a pressure of 1.33×10³Pa, amorphous TiN nanoparticles combined in the form of chains. Large Ir particulates with diameters of up to 2μm were particularly prominent in TiN–Ir films. Size distributions of the Ir particulates were dependent on ablation laser wavelength; that is, the diameter decreased at laser wavelength shortened. The TiN–Ir films with different Ir contents and morphologies on Ti substrates were evaluated as electrolysis electrodes for water disinfection. The highest current efficiency was 0.45%, which is comparable to that of conventional Ti–Pt electrodes, for a chloride-ion concentration of 9mgdm⁻³.

Keywords: PACS; 52.38.Mf; 79.20.DsLaser ablation; Nanoparticle; Particulate; Titanium nitride; Iridium; Electrolysis

MicroRaman study of the effect of oxide layer on nitriding of Ti–6Al–4V by C. Anandan; K.S. Rajam (pp. 2783-2789).

Ti–6Al–4V samples were subjected to nitrogen ion implantation and low pressure RF plasma nitriding in a PIII equipment after chemical etching in Kroll's reagent. The samples were characterized by optical microscopy, AFM, microRaman, XRD and micro hardness measurements. From microRaman, oxides of titanium were found in the inter-granular β region whereas the oxide on the α region was extremely thin. The oxide on the β region was found to be amorphous and from intensity dependent Raman spectra, it was found to have a layered structure. The top layer was rutile and the inner layer anastase. Presence of Ti₂O₃ was also found. After PIII treatment at 600°C, microRaman showed the presence of nitride in both the regions and the oxide was absent in the β regions. Also, from intensity dependent Raman spectra, it was found that in-take of nitrogen by β regions was higher. The oxide layer remained unaffected after plasma nitriding. Nitride presence in the α was established by microRaman. Even though Raman spectra from β regions were nearly the same as that of oxide, presence of nitrogen was indicated by the spectra. XRD studies of implanted and nitrided samples showed the prsence of TiN and Ti₂N in implanted sample and presence of Ti₂N in the nitrided sample. The β regions were found to have higher microhardness values after PIII and nitriding treatments. This is attributed to the deeper diffusion of nitrogen in these regions.

Keywords: PACS; 52.77.Dq; 81.65.Mq; 68.55.JkPlasma immersion ion implantation; Plasma nitriding; Ti–6Al–4V; MicroRaman; Nitrogen diffusion

Modified π-states in ion-irradiated carbon by G. Kovach; A. Karacs; G. Radnoczi; H. Csorbai; L. Guczi; M. Veres; M. Koos; L. Papadimitriou; A. Sólyom; G. Pető (pp. 2790-2796).

CVD polycrystalline diamond film, pulse laser-deposited (PLD) carbon film and highly oriented pirolitical graphite (HOPG) as reference, were modified by means of Ar⁺ ion bombardment and characterized by means of Raman scattering, transmission electron microscopy, electron-diffraction (TEM), reflected electron energy loss specroscopy (REELS) and X-ray photoelectron spectroscopy (XPS) techniques. It was found that the diamond was transferred to a carbon with halo-like morphology and disordered stack of graphene segments. Instead of the well-known electron energy loss peak of graphite at 6.5eV, a new REELS peak appeared at 4–5eV energies. The observed effect was explained by the modification of π-system in carbon films as a consequence of the formation of non-planar, nanometer-sized graphitic planes.

Keywords: Carbon; Diamond; Ion bombardment; REELS

Studies of craters’ dimension for long-pulse laser ablation of metal targets at various experimental conditions by D. Margarone; L. Láska; L. Torrisi; S. Gammino; J. Krása; E. Krouský; P. Parys; M. Pfeifer; K. Rohlena; M. Rosiñski; L. Ryc; J. Skála; J. Ullschmied; A. Velyhan; J. Wolowski (pp. 2797-2803).

Long pulse laser shots of the PALS iodine laser in Prague have been used to obtain metal target ablation at various experimental conditions. Attention is paid mainly to the dependencies of the crater diameter on the position of minimum laser-focus spot with regard to the target surface, by using different laser wavelengths and laser energies. Not only a single one, but two minima, independently of the wavelength, of the target irradiation angle and of the target material, were recorded. Significant asymmetries, ascribed to the non-linear effects of intense laser beam with pre-formed plasma, were found, too. Estimations of ejected mass per laser pulse are reported and used to calculate the efficiency of laser-driven loading. Results on metal target ablation and crater formation at high intensities (from 2×10¹³ to 3×10¹⁶W/cm²) are presented and compared. Crater depth, crater diameter and etching yield are reported versus the laser energy, in order to evaluate the ablation threshold fluence.

Keywords: PACS; 52.38.Mf; 52.38.HbLaser-plasmas; Craters; Focus position; Ablation threshold

Structural characterization of nc-Si films grown by low-energy PECVD on different substrates by A. Le Donne; S. Binetti; G. Isella; B. Pichaud; M. Texier; M. Acciarri; S. Pizzini (pp. 2804-2808).

The knowledge and control of the structural details (texture, crystallite environment and size) of nanocrystalline silicon films is a prerequisite for their proper application in various technological fields. To this purpose, nanocrystalline silicon films grown by low energy plasma enhanced chemical vapour deposition (LEPECVD) on different kinds of substrates were submitted to a systematic characterization using Raman spectroscopy, X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The results showed how the difference in substrate morphology is responsible for a deep difference in the film structural properties, particularly in the case of high silane dilutions.

Keywords: PACS; 81.07.Bc; 81.15.Gh; 68.55.Jk; 68.37.LpNanocrystalline silicon; LEPECVD; Raman in-depth profiles; XRD; HRTEM

Effects of coating parameters on the morphology of SiO₂-coated TiO₂ and the pigmentary properties by Yumin Liu; Chen Ge; Min Ren; Hengbo Yin; Aili Wang; Dongzhi Zhang; Chunyan Liu; Jun Chen; Hui Feng; Hengping Yao; Tingshun Jiang (pp. 2809-2819).

SiO₂-coated TiO₂ powders were prepared by the chemical deposition method starting from rutile TiO₂ and Na₂SiO₃. The SiO₂-coated TiO₂ powders were characterized by X-ray photoelectron spectroscopy, Zeta-potential analysis, Fourier transform infrared spectroscopy, and transmission electron microscopy. The evolution of island-like and uniform coating layers was found to depend upon the ratio of Na₂SiO₃ to TiO₂, reaction temperature, and pH. The whiteness and brightness of the SiO₂-coated TiO₂ powders increased in response to an increase in the SiO₂ loading, but there was a maximum value among the light scattering indexes. The SiO₂-coated TiO₂ powders possessed more negative Zeta potentials than the naked TiO₂. The dispersibility of the SiO₂-coated TiO₂ powders with the continuous and uniform SiO₂ coating layers was higher than that of the naked TiO₂ and the SiO₂-coated TiO₂ powders with the island-like SiO₂ coating layers.

Keywords: Rutile TiO; ₂; SiO; ₂; Island-like coating; Uniform coating; Pigmentary property

Chemical synthesis of nano-porous ruthenium oxide (RuO₂) thin films for supercapacitor application by V.D. Patake; C.D. Lokhande (pp. 2820-2824).

Ruthenium oxide (RuO₂) thin films have been prepared using single step chemical method containing Ru(III) Cl₃ solution in an aqueous medium at low temperature. The structural, morphological and optical properties have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and optical absorption technique. The XRD study revealed the formation of amorphous RuO₂ thin film. The surface examination by SEM showed formation of nano-porous material on the substrate. The TEM study revealed the formation of nanostructured material. The optical absorption studies showed the presence of direct band transition with band gap equal to 2.2eV. The RuO₂ has proved its applicability in supercapacitor showing 50F/g specific capacitance in 0.5M H₂SO₄ at 20mV/s scan rate.

Keywords: Ruthenium oxide; Chemical deposition; Thin films; Nano-porous; Supercapacitor

The role of adsorption of sodium bis(2-ethylhexyl) sulfosuccinate in wetting of glass and poly(methyl methacrylate) surface by Joanna Harkot; Bronisław Jańczuk (pp. 2825-2830).

Advancing contact angles, θ, for aqueous solutions of the anionic surfactant, sodium bis(2-ethylhexyl) sulfosuccinate (AOT) were measured on glass and poly(methyl methacrylate) (PMMA) surface. Using the obtained results we determined the properties of aqueous AOT solutions in wetting of these surfaces. It occurs that the wettability of glass and PMMA by these solutions depends on the concentration of AOT in solution. There is almost linear dependence between the contact angle ( θ) and concentration of AOT (log C) in the range from 5×10⁻⁴ to 2.5×10⁻³M/dm³ (value of the critical micelle concentration of AOT—CMC) both for glass and PMMA surface. For calculations of AOT adsorption at solid (glass, PMMA)-solution drop–air system interfaces the relationship between the adhesion tension ( γ_LVcos θ) and surface tension ( γ_LV) and the Gibbs and Young equations were taken into account. From the measurement and calculation results the slope of the γ_LVcos θ− γ_LV curve was found to be constant and equal 0.7 for glass and −0.1 for PMMA over the whole range of AOT concentration in solution. From this fact it can be concluded that if Γ_SV is equal zero then Γ_SL>0 for the PMMA–solution and Γ_SL<0 for glass–solution systems. It means that surfactant concentration excess at PMMA–solution interface is considerably lower than at solution-air interface, but this excess of AOT concentration at glass–solution interface is lower than in the bulk phase. By extrapolating the linear dependence between the adhesion and surface tension the value of the critical surface tension ( γ_c) of wetting for glass and PMMA was also determined, that equaled 25.9 and 25.6mN/m for glass and PMMA, respectively. Using the value of the glass and PMMA surface tension as well as the measured surface tension of aqueous AOT solutions in Young equation, the solid–liquid interface tension ( γ_SL) was found. There was a linear dependence between the γ_SL and γ_LV both for glass and PMMA, but there were different slope values of the curves for glass and PMMA, i.e. −0.7 and 0.1, respectively. The dependence between the work of adhesion ( W_A) and surface tension ( γ_LV) was also linear of different slopes for glass and for PMMA surface.

Keywords: PACS; 68.35 NpWettability; Surface tension; Glass; Poly(methyl methacrylate); Surfactant; Sodium bis(2-ethylhexyl) sulfosuccinate

Novel silsesquioxane mixture-modified high elongation polyurethane with reduced platelet adhesion by William Tao; Hongyang Zhou; Yan Zhang; Gang Li (pp. 2831-2836).

We have successfully synthesized a kind of novel silsesquioxane mixture that can be used to modify the surface of biomaterial polyurethane (PU) for the purpose of making silsesquioxane/PU as low-price and high-quality biomaterial. HPLC, FTIR and²⁹Si NMR are used to characterize as-synthesized silsesquioxane mixture. XPS figure and SEM images show the silsesquioxane particles really self-assemble on the PU surface. Contact angle measurements verify that there is a large hysteresis loop, which relates to low- and high-surface free energy component on the surface. Platelet adsorption at 90min of PU/silsesquioxane mixture is lower than that of poly(tetrafluoroethylene) (PTFE) and PU (two-way ANOVA, p<0.05). Furthermore, SEM images show “island” morphologic pattern with Cooper grades I platelet adsorption morphology on the smooth PU/silsesquioxane surface, and mechanic test shows that the samples with silsesquioxane mixture can increase mechanic property of PU. On the basis of these results, we conclude that this kind of nanocomposite has promise for application in biomaterials.

Keywords: Polyurethane; Surface modification; Island morphology

Photo-electrochemical analysis of passive film formed on X80 pipeline steel in bicarbonate/carbonate buffer solution by D.G. Li; Y.R. Feng; Z.Q. Bai; J.W. Zhu; M.S. Zheng (pp. 2837-2843).

Photo-electrochemical measurement was used to explore the formation potential, formation time, chloride ions concentration, applied potential and pH value of the solution on the electronic property of passive film formed on X80 pipeline steel in 1M NaHCO₃/0.5M Na₂CO₃ buffer solution. The results showed that the photocurrent is positive, indicating an n-type semiconductor character of the passive film, the photocurrent increased with increasing the formation potential, prolonging the formation time, decreasing chloride ions concentration, rising applied potential and decreasing the pH value of the solution. Capacitance measurement exhibited a positive slope of Mott-Schottky plot, and the slopes of Mott-Schottky plots increased with the increasing formation potential, showing a decrement of the donor density of the passive film.

Keywords: Passive film; Photo-electrochemical measurement; Capacitance measurement; Mott-Schottky analysis

Composition of calcium deficient Na-containing carbonate hydroxyapatite modified with Cu(II) and Zn(II) ions by Jidong Li; Yubao Li; Li Zhang; Yi Zuo (pp. 2844-2850).

In this paper, the compositions of calcium deficient Na-containing carbonate hydroxyapatite (NaCHA) modified with Cu(II) and Zn(II) ions was studied by means of ICP, XPS and FTIR. The obtained results indicate that NaCHA is more soluble in ion-exchange medium, resulting in the incorporation of more metal ions. The ICP and XPS analyses indicate that the enrichment of Zn²⁺ is more than that of Cu²⁺ on the surface. Moreover, Cu²⁺ ions have substituted for Ca²⁺ and Na⁺ ions and also enter into the vacancy and/or the hexagonal channels in NaCHA lattice. The above results indicate that NaCHA modified with Cu²⁺ and Zn²⁺ displays a predominant dissolution–precipitation or coprecipitation mechanism and at the same time, adsorption and diffusion mechanism maybe also exist.

Keywords: PACS; TQ 455Calcium deficient carbonate hydroxyapatite; Surface composition; Cu; ²⁺; and Zn; ²⁺; modification

Characterization of diamond (100) surface with oxygen termination by Run Long; Ying Dai; Meng Guo (pp. 2851-2855).

Ab initio density functional theory (DFT) was employed to study reconstructions of diamond (100) surfaces in the presence of hydrogen, oxygen and hydroxyl. Clean and (2×1):1H surfaces are taken as reference. The properties of oxidization diamond surfaces with several adsorption structures, namely, O-on-top (OT) site, O-bridge (BR) site, hydroxyl (–OH), hydroxyl/hydroxyl, OT/hydroxyl, BR/hydroxyl have been considered. The calculated results indicate that the BR model is much more stable than the OT model, and the most energetically favorable structures of oxygenated surfaces are those with chemisorbed hydroxyl (–OH) group. Furthermore, the stability of the structures is also discussed from the point of HOMO–LUMO gap. Analysis of electronic structures shows that the presence of hydrogen induces surface conductivity whereas oxygen weakens it.

Keywords: Density functional theory; Diamond (1; 0; 0) surface; Adsorption

The characteristic of photoelectric gas sensing to oxygen and water based on ZnO nanoribbons at room temperature by Liang Peng; Dejun Wang; Min Yang; Tengfeng Xie; Qidong Zhao (pp. 2856-2860).

In this article, ZnO nanoribbons were prepared by multi-components precursor self-assembled method, and the characteristic of photoelectric gas sensing of the nanoribbons was investigated on exposure of oxygen and water environments by surface photocurrent technique. The results showed that surface photocurrent intensity (SPI) was enhanced after oxygen and water adsorption. This increase of SPI was attributed mostly to the improvement of carriers-generating efficiency. And the mechanism was discussed in detail.

Keywords: ZnO nanoribbons; Gas sensing; Surface photocurrent; Oxygen

Surface characteristics and nanoindentation study of Ni–Mn–Ga ferromagnetic shape memory sputtered thin films by C. Liu; Z.Y. Gao; X. An; H.B. Wang; L.X. Gao; W. Cai (pp. 2861-2865).

In present paper, the off-stoichiometric Ni–Mn–Ga ferromagnetic shape memory alloy thin films are fabricated using radio frequency magnetron sputtering method. The compositions, microstructures and mechanical properties of the thin films are characterized by energy dispersive X-ray spectrum (EDAX), X-ray photoelectron spectroscopy (XPS), scanning electronic microscope (SEM), atomic force microscope (AFM) and nanoindentation test, respectively. The results show that there is a thinner layer of oxides consisting of NiO, Ga₂O₃ and an unspecified manganese oxidation (Mn_xO_y) at the surface, whereas a small amount of MnO precipitates exist in internal layers of post-annealed Ni–Mn–Ga thin films. The hardness and elastic modulus decrease with increasing film thickness. Nanoindentation tests reveal that the hardness and elastic modulus of the films can be up to 5.5 and 155GPa, respectively. The Ni–Mn–Ga thin films have remarkably improved the ductility of Ni–Mn–Ga ferromagnetic shape memory alloys bulk materials.

Keywords: Ni–Mn–Ga; Ferromagnetic shape memory alloys; Thin film; Nanoindentation

Auger electron spectroscopic study of CO₂ adsorption on Zircaloy-4 surfaces by N. Stojilovic; N. Farkas; R.D. Ramsier (pp. 2866-2870).

We investigate the adsorption of CO₂ onto Zircaloy-4 (Zry-4) surfaces at 150, 300 and 600K using Auger electron spectroscopy (AES). Following CO₂ adsorption at 150K the graphitic form of carbon is detected, whereas upon chemisorption at 300 and 600K we detect the carbidic phase. As the adsorption temperature is increased, the carbon Auger signal increases, whereas the oxygen signal decreases. Adsorption at all three temperatures results in a shift of the Zr Auger features, indicating surface oxidation. The effect of adsorbed CO₂ on the Zr(MVV) and Zr(MNV) transitions depends on adsorption temperature and is less pronounced at higher temperatures. On the other hand, changes in the Zr(MNN) feature are similar for all three adsorption temperatures. The changes in the Zr Auger peak shapes and positions are attributed to oxygen from dissociated CO₂, with the differences observed at various temperatures indicative of the diffusion of oxygen into the subsurface region.

Keywords: Zry-4; CO; ₂; AES; Carbidic carbon; Graphitic carbon

The influence of surface microchemistry in protective film formation on multi-phase magnesium alloys by J.E. Gray-Munro; B. Luan; L. Huntington (pp. 2871-2877).

The high strength:weight ratio of magnesium alloys makes them an ideal metal for automotive and aerospace applications where weight reduction is of significant concern. Unfortunately, magnesium alloys are highly susceptible to corrosion particularly in salt-spray conditions. This has limited their use in the automotive and aerospace industries, where exposure to harsh service conditions is unavoidable. The simplest way to avoid corrosion is to coat the magnesium-based substrate by a process such as electroless plating, which is a low-cost, non line of sight process.Magnesium is classified as a difficult to plate metal due to its high reactivity. This means that in the presence of air magnesium very quickly forms a passive oxide layer that must be removed prior to plating. Furthermore, high aluminium content alloys are especially difficult to plate due to the formation of intermetallic species at the grain boundaries, resulting in a non-uniform surface potential across the substrate and thereby further complicating the plating process.The objective of this study is to understand how the magnesium alloy microstructure influences the surface chemistry of the alloy during both pretreatment and immersion copper coating of the substrate.A combination of scanning electron microscopy, energy dispersive spectroscopy and scanning Auger microscopy has been used to study the surface chemistry at the various stages of the coating process. Our results indicate that the surface chemistry of the alloy is different on the aluminum rich β phase of the material compared to the magnesium matrix which leads to preferential deposition of the metal on the aluminum rich phase of the alloy.

Keywords: Magnesium alloys; Electroless plating; Fluoride; Copper; Metallization

Indium zinc oxide thin films deposited by sputtering at room temperature by Wantae Lim; Yu-Lin Wang; F. Ren; D.P. Norton; I.I. Kravchenko; J.M. Zavada; S.J. Pearton (pp. 2878-2881).

The deposition of amorphous indium zinc oxide (IZO) thin films on glass substrates with n-type carrier concentrations between 10¹⁴ and 3×10²⁰cm⁻³ by sputtering from single targets near room temperature was investigated as a function of power and process pressure. The resistivity of the films with In/Zn of ∼0.7 could be controlled between 5×10⁻³ and 10⁴Ωcm by varying the power during deposition. The corresponding electron mobilities were 4–18cm²V⁻¹s⁻¹.The surface root-mean-square roughness was <1nm under all conditions for film thicknesses of 200nm. Thin film transistors with 1μm gate length were fabricated on these IZO layers, showing enhancement mode operation with good pitch-off characteristics, threshold voltage 2.5V and a maximum transconductance of 6mS/mm. These films look promising for transparent thin film transistor applications.

Keywords: Indium zinc oxide; Sputtering; Thin film transistors

Studies on surface modification of poly(tetrafluoroethylene) film by remote and direct Ar plasma by Wang Chen; Chen Jie-rong; Li Ru (pp. 2882-2888).

Poly(tetrafluoroethylene) (PTFE) surfaces are modified with remote and direct Ar plasma, and the effects of the modification on the hydrophilicity of PTFE are investigated. The surface microstructures and compositions of the PTFE film were characterized with the goniometer, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Results show that the remote and direct plasma treatments modify the PTFE surface in morphology and composition, and both modifications cause surface oxidation of PTFE films, in the forming of some polar functional groups enhancing polymer wettability. When the remote and direct Ar plasma treats PTFE film, the contact angles decrease from the untreated 108–58° and 65.2°, respectively. The effect of the remote Ar plasma is more noticeable. The role of all kinds of active species, e.g. electrons, ions and free radicals involved in plasma surface modification is further evaluated. This shows that remote Ar plasma can restrain the ion and electron etching reaction and enhance radical reaction.

Keywords: Remote and direct Ar plasma; Poly(tetrafluoroethylene); Surface modification

Effect of surface preparation technique on the radiation detector performance of CdZnTe by M.C. Duff; D.B. Hunter; A. Burger; M. Groza; V. Buliga; D.R. Black (pp. 2889-2892).

Synthetic CdZnTe (CZT) semiconducting crystals are highly suitable for the room temperature-based detection of gamma radiation. The surface preparation of Au contacts on surfaces of CZT detectors is typically conducted after (1) polishing to remove artifacts from crystal sectioning and (2) chemical etching, which removes residual mechanical surface damage however etching results in a Te rich surface layer that is prone to oxidize. Our studies show that CZT surfaces that are only polished (as opposed to polished and etched) can be contacted with Au and will yield lower surface currents. Due to their decreased dark currents, these as-polished surfaces can be used in the fabrication of gamma detectors exhibiting a higher performance than polished and etched surfaces with relatively less peak tailing and greater energy resolution.

Keywords: Radiation detectors; X-ray topography (crystal defects); Resistivity; X-ray topographic imaging

Direct synthesis and characterization of highly ordered functional mesoporous silica thin films with high amino-groups content by Xueao Zhang; Wenjian Wu; Jianfang Wang; Xiaozhou Tian (pp. 2893-2899).

A series of continuous, crack-free, highly ordered amino-functionalized mesoporous silica thin films have been directly synthesized by co-condensation of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) in the presence of cationic CH₃(CH₂)₁₅N⁺(CH₃)₃Br⁻ (CTAB), nonionic C₁₆H₃₃(OCH₂CH₂)₁₀OH (Brij-56) or triblock copolymer H(OCH₂CH₂)₂₀(OCH(CH₃)CH₂)₇₀(OCH₂CH₂)₂₀)OH (P123) surfactant species under acidic conditions by sol–gel dip-coating. The molar ration of APTES/(TEOS+APTES) in the starting sol attains a value of 0.4. The effect of the sol aging on the mesostructure of thin films is systematically studied, and the optimal sol aging time is obtained for different surfactant systems. The amino-functionalized mesoporous silica thin films exhibit long-range ordering of 2D hexagonal ( p6 mm) and 3D cubic ( Fm3 m) pore arrays of size range from 2.2 to 8.3nm following surfactants extraction as demonstrated by XRD, TEM and physical adsorption techniques. Based on BET surface area and weight loss, the surface coverage of amino-groups for thin films prepared using different surfactants is calculated to be 3.2 and above amino-groups per nm², which is very useful and promising for incorporating inorganic ions and biomolecules into these mesoporous silica materials.

Keywords: Mesoporous silica; Thin films; Amino-groups; Surface functionalization; Co-condensation

Optical and electrical properties of p-type ZnO fabricated by NH₃ plasma post-treated ZnO thin films by P. Cao; D.X. Zhao; J.Y. Zhang; D.Z. Shen; Y.M. Lu; B. Yao; B.H. Li; Y. Bai; X.W. Fan (pp. 2900-2904).

In this paper, a simple method is reported to obtain nitrogen-doped p-ZnO film. In this method NH₃ plasma, generated in a plasma-enhanced chemical vapor deposition system, was employed to treat ZnO thin film. By Hall-effect measurement, a p-type conductivity was observed for the treated film with the hole density of 2.2×10¹⁶cm⁻³. X-ray photoelectron spectroscopy (XPS) results confirmed that nitrogen was incorporated into ZnO film during the treatment process to occupy the oxygen positions. In low temperature photoluminescence spectra, an emission peak corresponding to acceptor–donor pair was observed. From this emission peak we calculated the N-related acceptor binding energy to be 130meV.

Keywords: p-type ZnO; Nitrogen doping; NH; ₃; plasma

Surface evolution of a gradient structured Ti in hydrogen peroxide solution by Ming Wen; Jian-Feng Gu; Gang Liu; Zhen-Bo Wang; Jian Lu (pp. 2905-2910).

In this work, the interaction between hydrogen peroxide (H₂O₂) and a gradient structured Ti was investigated extensively. The gradient structured Ti (SMAT Ti) was produced by surface mechanical attrition treatment (SMAT), and then it was immersed in H₂O₂ solution for different time until 48h at room temperature (25°C). The structure and surface morphology evolution were examined by Raman spectra and scanning electron microscopy (SEM). The formation mechanism of nanoporous titania was discussed based on above results.

Keywords: PACS; 61.46.HK; 68.35.BSGradient structure; Titanium; Nanoporous; titania

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Applied Surface Science (v.254, #9)

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Applied Surface Science (v.254, #9)