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Applied Surface Science (v.254, #6)

Morphology of sol–gel produced composite films for optical oxygen sensors by S. Anastasova; M. Milanova; E. Kashchieva; H. Funakubo; T. Kamo; N. Grozev; P. Stefanov; D. Todorovsky (pp. 1545-1558).

The results reported concern the characterization of thin layer SiO₂-based matrices with an oxygen sensing component Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline) immobilized, when a sol–gel process along with dip- and spin-coating deposition methods are used.SEM, TEM and AFM study, assisted by X-ray energy dispersive microanalysis reveals the influence of the precursors used, sol treatment and the coating conditions on the films morphology and Ru distribution in the matrices. Uniform and smooth surface is produced from tetraethoxysilane (TEOS). The presence of ormosils (methyltriethoxysilane, MtEOS and octyltriethoxysilane, OtEOS) significantly increases the surface roughness exhibited as dots on the SEM image. Their surface concentration and size depend on the number of immersions and withdrawal speed at the dip coating. Spin deposition leads to rather different morphology of the films, based on TEOS/OtEOS. Following commonly used sol preparation procedure (with 1.25–2.5gRu-complex/dm³sol) microcrystallization of the complex occurs with formation of randomly distributed crystals 100–400nm in size. The ultrasound treatment of the sol by means of ultrasound disintegrator leads to homogeneous distribution of the complex without observable crystallization and significant improvement of the film sensing properties (increase of Stern–Volmer constant and better linearity of the Stern–Volmer plots both in gaseous and aqueous media).

Keywords: PACS; 68.37.Hk; 68.37.Lp; 68.37.Ps; 68.55.−aThin films; Oxygen sensors; Morphology; Electron microscopy; Sol–gel method; Dip coating; Spin coating; Sonication

Effects of cutting depth on the surface microstructure of a Zn–Al alloy during ultra-precision machining by S. To; Y.H. Zhu; W.B. Lee (pp. 1559-1564).

The microstructural changes and phase decomposition at the surface of an ultra-precision machined Zn–Al based alloy were studied using optical microscopy, back-scattered electron microscopy, electron back-scattered diffraction and X-ray diffraction techniques. It was found that with increasing DoC the phase decomposition was accelerated and further increasing DoC might cause a microstructural recovery on the surface of the UPM specimen. UPM induced phase decomposition was discussed in relation to the structural evolution of the chips.

Keywords: Ultra-precision machining; Microstructure; Phase decomposition; Zn–Al alloy

Study on the orientation of silver films by ion-beam assisted deposition by Tao Feng; Bingyao Jiang; Sun Zhuo; Xi Wang; Xianghuai Liu (pp. 1565-1568).

Low energy ion beam assisted deposition (IBAD) was employed to prepare Ag films on Mo/Si (100) substrate. It was found that Ag films deposited by sputtering method without ion beam bombardment were preferred (111) orientation. When the depositing film was simultaneously bombardment by Ar⁺ beam perpendicular to the film surface at ion/atom arrival ratio of 0.18, the prepared films exhibited weak (111) and (200) mixed orientations. When the direction of Ar⁺ beam was off-normal direction of the film surface, Ag films showed highly preferred (111) orientation. Monte Carlo method was used to calculate the sputtering yields of Ar⁺ ions at various incident and azimuth angles. The effects of channeling and surface free energy on the crystallographic orientation of Ag films were discussed.

Keywords: PACS; 68.55.Jk; 81.15.JjPreferred orientation; Ion beam assisted deposition; Ag film

Structural characterization of polycrystalline Ag–In–Se thin films deposited by e-beam technique by T. Çolakoğlu; M. Parlak (pp. 1569-1577).

The Ag–In–Se thin films were deposited by e-beam evaporation of theAg3In5Se9 single crystal powder under high vacuum without intentional doping. Energy dispersive X-ray analysis (EDXA) showed the decreasing behavior of Se and Ag in the structure depending on the annealing. X-ray diffraction (XRD) analysis showed that as-grown films have amorphous structure while annealing the films under nitrogen environment at 200 °C transformed from the amorphous to polycrystalline structure. The crystallinity of the films improved as annealing temperature increases up to 400 °C by 100 °C-step. The polycrystalline films show mixed binary and ternary crystalline phases. Each phase was determined by comparing XRD patterns with complete data cards as Ag₃In₅Se₉, AgInSe₂, In₄Se₃, In₂Se₃, InSe, Se₆ and Se. The existence of Se segregation was supported by the formation of Se aggregates in crystalline phases of Se₆ and Se. The X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analysis have been carried out in order to obtain detailed information about the atomic composition, chemical states and morphology of the thin film surface. The decomposition of In 4d, Se 3d and Ag 3d photoelectron peaks revealed the existence of In–In, In–Se, In–Ag, Se–Se and Ag–Ag bondings in as-grown thin films. After annealing the thin films at different temperatures, the concentration of In–Se and In–Ag bonds decreases significantly, which results in an In-rich, but Ag- and Se-deficient thin film structure. The roughness of the film surface as a result of application of post-annealing in between 200 and 400 °C monitored by AFM technique was observed to change from 1.81 to 22.89 nm.

Keywords: Silver indium selenide; Ternary compounds; Selenium segregation; XPS; AFM; XRD

The structural and optical properties of ZnO/Si thin films by RTA treatments by S.Y. Hu; Y.C. Lee; J.W. Lee; J.C. Huang; J.L. Shen; W. Water (pp. 1578-1582).

ZnO/Si thin films were prepared by rf magnetron sputtering method and some of the samples were treated by rapid thermal annealing (RTA) process at different temperatures ranging from 400 to 800°C. The effects of RTA treatment on the structural properties were studied by using X-ray diffraction and atomic force microscopy while optical properties were studied by the photoluminescence measurements. It is observed that the ZnO film annealed at 600°C reveals the strongest UV emission intensity and narrowest full width at half maximum among the temperature ranges studied. The enhanced UV emission from the film annealed at 600°C is attributed to the improved crystalline quality of ZnO film due to the effective relaxation of residual compressive stress and achieving maximum grain size.

Keywords: PACS; 61.72.Cc; 68.55.Jk; 78.55.−m; 81.40.EfZnO thin films; Rapid thermal annealing; Photoluminescence

Ferroelectric properties of bilayer structured Pb(Zr_0.52Ti_0.48)O₃/SrBi₂Ta₂O₉ (PZT/SBT) thin films on Pt/TiO₂/SiO₂/Si substrates by Wen-Qi Zhang; Ai-Dong Li; Qi-Yue Shao; Yi-Dong Xia; Di Wu; Zhi-Guo Liu; Nai-Ben Ming (pp. 1583-1586).

Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin films with large remanent polarization and SrBi₂Ta₂O₉ (SBT) thin films with excellent fatigue-resisting characteristic have been widely studied for non-volatile random access memories, respectively. To combine these two advantages_, bilayered Pb(Zr_0.52Ti_0.48)O₃/SrBi₂Ta₂O₉ (PZT/SBT) thin films were fabricated on Pt/TiO₂/SiO₂/Si substrates by chemical solution deposition method. X-ray diffraction patterns revealed that the diffraction peaks of PZT/SBT thin films were completely composed of PZT and SBT, and no other secondary phase was observed. The electrical properties of the bilayered structure PZT/SBT films have been investigated in comparison with pure PZT and SBT films. PZT/SBT bilayered thin films showed larger remanent polarization (2 P_r) of 18.37μC/cm² than pure SBT and less polarization fatigue up to 1×10⁹ switching cycles than pure PZT. These results indicated that this bilayered structure of PZT/SBT is a promising material combination for ferroelectric memory applications.

Keywords: Pb(Zr; _0.52; Ti; _0.48; )O; ₃; (PZT); SrBi; ₂; Ta; ₂; O; ₉; (SBT); Chemical solution deposition (CSD); Bilayered structure

Modification of Au surfaces using new ferrocene derivatives by Tanya L. Díaz-Ortiz; María Malavé-León; Mirna Rivera-Claudio; Jorge Castillo-Ramírez; Carlos R. Cabrera-Martínez; Rosa Brito-Gómez; Rolando J. Tremont (pp. 1587-1592).

Gold surfaces have been modified by self-assembled techniques. Here the adsorption time of diasteroisomers (1 R, 3 S)-1-ferrocenyl-3-methyl-4,4-diphenyl-2,5-dioxacyclopentane and (1 S, 3 S)-1-ferrocenyl-3-methyl-4,4-diphenyl-2,5-dioxacyclopentane (,3a and3b) at a Au surface in ethanol solution was controlled. This study was followed by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) analysis. The method used for the surface modification was the control of exposure time of a Au surface in the modifier/ethanol solution. It was demonstrated by EIS and XPS that the Au surface was modified with mixture of compounds3a+3b, avoiding the electron transference in the interface. It was also observed that the organometallic molecule indeed had been adsorbed on the Au surface. In addition, evidence seems to conclude that the molecule-Au interaction is through the electrons of cyclopentadienyl moiety, where the oxygen atoms are near the air-molecule interface and the iron atom is near the Au surface. This type of interaction of the ferrocene derivatives with gold surfaces has not been reported by any other author.

Keywords: Self-assembled monolayer; Diasteroisomers (1; R; , 3; S; )-1-ferrocenyl-3-methyl-4,4-diphenyl-2,5-dioxacyclopentane; (1; S; , 3; S; )-1-Ferrocenyl-3-methyl-4,4-diphenyl-2,5-dioxacyclopentane; Au; Ferrocene derivatives; EIS; XPS

Facile method to prepare lotus-leaf-like super-hydrophobic poly(vinyl chloride) film by Zhiqing Yuan; Hong Chen; Jide Zhang (pp. 1593-1598).

A simple new approach was developed to obtain a super-hydrophobic PVC film from a natural lotus leaf using the nanocasting method. SEM shows that compared with a common smooth PVC film, a lotus-leaf-like surface structure was clearly observed on the super-hydrophobic PVC film. The water contact angle and rolling-off angle on the as-prepared lotus-leaf-like PVC film were 157±1.8° and 3±0.6°, respectively. The samples were kept at temperatures between 5 and 40°C in the ambient atmosphere for 2 months, and no decrease in water contact angle was observed, nor was contamination observed.

Keywords: Super-hydrophobic; Lotus leaf; Nanocasting

Ultraviolet emission properties of ZnO film with zinc deficiency by SS CVD by Liping Dai; Hong Deng; Geng Chen; Jinju Chen (pp. 1599-1603).

A– b axis orientation ZnO film on silicon (100) substrate has been prepared by a single source chemical vapor deposition technique. X-ray photoelectron spectroscopy results revealed that the film was very close to stoichiometry but with a small amount of zinc deficiency. Temperature-dependent (10–300K) ultraviolet photoluminescence of the film was presented. Comparing the photon energy separation of the several groups in the near band edge ultraviolet luminescence bands, as well as the variation of the relative intensities and the shift of the luminescence lines at different temperatures, free-, bound-exciton and its assisted phonon emission were observed, which corresponded to the mechanism of the ultraviolet emission properties. A strong ultraviolet emission resulting from the recombination of free-exciton was observed at 300K photoluminescence spectrum examined in atmosphere environment. Contrasted to the relatively weak ultraviolet emission of the film in vacuum, atmosphere environment was found to be an important contribution to the strong ultraviolet emission of the film.

Keywords: Ultraviolet photoluminescence; ZnO thin films; A; –; b; axis orientation; SS CVD

Study of Al₂O₃/TiO₂ reflectivity enhancing bi-layer films on bright aluminium substrates by L. Cecchetto; C. Millon; D. Riassetto; M. Langlet (pp. 1604-1607).

Al₂O₃/TiO₂ bi-layer films on aluminium substrates have been obtained by combining anodising and TiO₂ sol–gel deposition. The reflectivity enhancing properties of these Al₂O₃/TiO₂ bi-layer films have been studied in relation to the refractive index and thickness of the Al₂O₃ and TiO₂ single-layers. It is shown that a significant improvement of reflectivity can be achieved by a proper optimisation of the bi-layer elaboration parameters.

Keywords: Aluminium; Reflectivity; Al; ₂; O; ₃; layers; TiO; ₂; layers; Anodising; Sol–gel process

Micro-Arc oxidation of Ti in a solution of sulfuric acid and Ti⁺³ salt by Rimas Ragalevičius; Giedrius Stalnionis; Gediminas Niaura; Arūnas Jagminas (pp. 1608-1613).

A comparative study was performed on the behavior of titanium electrode in a sulfuric acid solution with and without Ti⁺³ during micro-arc oxidation under the constant current density control regime. The composition and microstructure of the obtained micro-arc films were analyzed using scanning electron microscopy, glancing-angle X-ray diffractometry, Raman and energy-dispersive X-ray spectroscopies.We have shown that addition of a Ti⁺³ salt extends the region of current densities ( j_a) can be used for micro-arc oxidation of Ti and results in an obvious change of sparking behavior from extensive, large and long-played sparks to numerous, small and short sparks. As a consequence, the titania films formed in the Ti⁺³-containing solutions are relatively thick, more uniform, composed of almost pure crystalline anatase and rutile phases of TiO₂, and contain a network of evenly distributed small pores. It has also been shown that these films are promising for applications in catalysis, sensors and optoelectronics. The Raman spectra indicate that an increase in the electrolysis time of titanium in the Ti⁺³-containing solution leads to the increase in rutile content, as expected.

Keywords: PACS; 86.68.+z; 81.65.HqMicro-arc oxidation; Titania; Phase composition

The effect of nitrogen and oxygen plasma on the wear properties and adhesion strength of the diamond-like carbon film coated on PTFE by K. Ozeki; K.K. Hirakuri (pp. 1614-1621).

Diamond-like carbon (DLC) films were deposited on polytetrafluoroethylene (PTFE) using a radiofrequency plasma chemical vapour deposition method. Prior to DLC coating, the PTFE substrates were modified with O₂ and N₂ plasma to enhance the adhesion strength of the DLC film to the substrate. The effect of the plasma pre-treatment on the chemical composition and the surface energy of the plasma pre-treated PTFE surface was investigated by X-ray photoelectron spectroscopy (XPS) and static water contact angle measurement, respectively. A pull-out test and a ball-on-disc test were carried out to evaluate the adhesion strength and the wear properties of the DLC-coated PTFE.In the N₂ plasma pre-treatment, the XPS result indicated that defluorination and the nitrogen grafting occurred on the plasma pre-treated PTFE surface, and the water contact angle decreased with increasing the plasma pre-treatment time. In the O₂ plasma pre-treatment, no grafting of the oxygen occurred, and the water contact angle slightly increased with the treatment time. In the pull-out test, the adhesion strength of the DLC film to the PTFE substrate was improved with the plasma pre-treatment to the PTFE substrate, and N₂ plasma pre-treatment was more effective than the O₂ plasma pre-treatment. In the ball-on-disc test, the DLC film with the N₂ plasma pre-treatment showed good wear resistance, compared with that with O₂ plasma pre-treatment.

Keywords: Diamond-like carbon; PTFE; Chemical vapour deposition; Plasma; Adhesion; Wear property

Topographic characterization of glazed surfaces by Linda Fröberg; Leena Hupa (pp. 1622-1629).

Detailed characterization of surface microstructure, i.e. phase composition and surface geometry, has become an important criterion of glazed ceramics. Topographic characterization is an important parameter in, e.g. estimating the influence of additional films on the average roughness of a surface. Also, the microscaled and nanoscaled roughnesses correlate with the cleanability and the self-cleaning properties of the surfaces. In this work the surface geometry of several matte glazes were described by topography and roughness as given by whitelight confocal microscopy and atomic force microscopy. Different measuring parameters were compared to justify the usefulness of the techniques in giving a comprehensive description of the surface microstructure. The results suggest that confocal microscopy is well suited for giving reliable topographical parameters for matte surfaces with microscaled crystals in the surfaces. Atomic force microscopy was better suited for smooth surfaces or for describing the local topographic parameters of closely limited areas, e.g. the surroundings of separate crystals in the surface.

Keywords: PACS; 81.05.Je; 81.05.KfAtomic force microscopy; Confocal microscopy; Glazes; Microstructure; Topography; Roughness

Enhanced photocatalytic activity of TiO₂ nano-structured thin film with a silver hierarchical configuration by Jinyu Zheng; Hua Yu; Xinjun Li; Shanqing Zhang (pp. 1630-1635).

TiO₂ sol–gels with various Ag/TiO₂ molar ratios from 0 to 0.9% were used to fabricate silver-modified nano-structured TiO₂ thin films using a layer-by-layer dip-coating (LLDC) technique. This technique allows obtaining TiO₂ nano-structured thin films with a silver hierarchical configuration. The coating of pure TiO₂ sol–gel and Ag-modified sol–gel was marked as T and A, respectively. According to the coating order and the nature of the TiO₂ sol–gel, four types of the TiO₂ thin films were constructed, and marked as AT (bottom layer was Ag modified, surface layer was pure TiO₂), TA (bottom layer was pure TiO₂, surface layer was Ag modified), TT (pure TiO₂ thin film) and AA (TiO₂ thin film was uniformly Ag modified). These thin films were characterized by means of linear sweep voltammetry (LSV), X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy and transient photocurrent ( I_ph). LSV confirmed the existence of Ag⁰ state in the TiO₂ thin film. SEM and XRD experiments indicated that the sizes of the TiO₂ nanoparticles of the resulting films were in the order of TT>AT>TA>AA, suggesting the gradient Ag distribution in the films. The SEM and XRD results also confirmed that Ag had an inhibition effect on the size growth of anatase nanoparticles. Photocatalytic activities of the resulting thin films were also evaluated in the photocatalytic degradation process of methyl orange. The preliminary results demonstrated the sequence of the photocatalytic activity of the resulting films was AT>TA>AA>TT. This suggested that the silver hierarchical configuration can be used to improve the photocatalytic activity of TiO₂ thin film.

Keywords: Photocatalysis; TiO; ₂; thin film; Ag loading

Microstructure and mechanical properties of Al₂O₃–Al composite coatings deposited by plasma spraying by Zhijian Yin; Shunyan Tao; Xiaming Zhou; Chuanxian Ding (pp. 1636-1643).

Al₂O₃ and Al₂O₃–Al composite coatings were prepared by plasma spraying. Phase composition of powders and as-sprayed coatings was determined by X-ray diffraction (XRD), while optical microscopy (OM) and scanning electron microscopy (SEM) were employed to investigate the morphology of impacted droplets, polished and fractured surface, and the element distribution in terms of wavelength-dispersive spectrometer (WDS). Mechanical properties including microhardness, adhesion and bending strength, fracture toughness and sliding wear rate were evaluated. The results indicated that the addition of Al into Al₂O₃ was beneficial to decrease the splashing of impinging droplets and to increase the deposition efficiency. The Al₂O₃–Al composite coating exhibited homogeneously dispersed pores and the co-sprayed Al particles were considered to be distributed in the splat boundary. Compared with Al₂O₃ coating, the composite coating showed slightly lower hardness, whereas the coexistence of metal Al phase and Al₂O₃ ceramic phase effectively improved the toughness, strength and wear resistance of coatings.

Keywords: Plasma spraying; Al; ₂; O; ₃; –Al composite; Microstructure; Mechanical properties

Surface characterization of the Zn–Ni–Al₂O₃ nanocomposite coating fabricated under ultrasound condition by Huan-yu Zheng; Mao-zhong An; Jun-feng Lu (pp. 1644-1650).

Zn–Ni–Al₂O₃ nanocomposite coating, which was fabricated by eletrodeposition technique with the aid of ultrasound, was investigated by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and X-ray photoelectron spectroscopy (XPS). The results reveal that 7.2wt.% nano-alumina particles uniformly dispersed in the matrix of the composite coating. The XPS analyses demonstrate that the outermost layer of Zn–Ni–Al₂O₃ coating was composed of nano-alumina and Zn(OH)₂, while the transition layer between the outermost layer and the Zn–Ni matrix consisted of nano-alumina, metallic Zn, ZnO and metallic Ni. In order to investigate the influences of ultrasonic agitation and the incorporation of nano-alumina on the composition and surface structure of Zn–Ni matrix, the comparison studies of Zn–Ni–Al₂O₃ nanocomposite coating with Zn–Ni coatings fabricated with and without ultrasound were conducted. The results indicate that ultrasonic agitation resulted in a decrease of Ni content in the Zn–Ni matrix and an increase of the thickness of surface oxide layer; while the incorporation of nano-α-Al₂O₃ increased the Ni content in the Zn–Ni matrix.

Keywords: PACS; 81.07.−bXPS; Electrodeposition; Ultrasound; Zn–Ni; Alumina; Nanocomposite coating

Synthesis and characterization of pure and ZrO₂-doped nanocrystalline CuO–NiO system by G.A. El-Shobaky; Nagi R.E. Radwan; M. Samy El-Shall; A.M. Turky; Hassan M.A. Hassan (pp. 1651-1660).

The physicochemical, surface and catalytic properties of pure and doped 0.25CuO–NiO solids prepared by sol–gel method were investigated. The dopant concentration was 2, 4 and 6mol% ZrO₂. The solids investigated were calcined at 400 and 600°C. The techniques employed were XRD, EDX, TEM, surface excess oxygen, nitrogen adsorption at −196°C and catalytic oxidation of CO by O₂ using both static and flow methods. The results revealed that the investigated system dissolved 4mol% ZrO₂ by heating at 400°C. This process was accompanied by a significant increase in the S_BET and V_p with subsequent decrease in the ( r) values of the doped adsorbent. ZrO₂-doping of the system investigated followed by calcination at 400 and 600°C led to a considerable increase in its catalytic activity in CO oxidation by O₂ using static and flow methods. The doping process was not accompanied by any change in the activation energy of the catalyzed reaction.

Keywords: CuO–NiO system; Nanocrystalline solids; CO oxidation by O; ₂

High mobility W-doped In₂O₃ thin films: Effect of growth temperature and oxygen pressure on structural, electrical and optical properties by R.K. Gupta; K. Ghosh; S.R. Mishra; P.K. Kahol (pp. 1661-1665).

Highly conducting and transparent thin films of tungsten (W)-doped indium oxide were obtained using pulsed laser deposition to study the effect of growth temperature and oxygen pressure on structural, optical and electrical properties. The transparency of the films is seen to largely depend on the growth temperature. The electrical properties, however, are found to depend strongly on both the growth temperature and the oxygen pressure. High mobility (up to 358cm²V⁻¹s⁻¹), low resistivity (1.1×10⁻⁴Ωcm), and relatively high transmittance (∼90%) tungsten-doped indium oxide films have been prepared at a growth temperature of 500°C and an oxygen pressure of 1×10⁻⁶bar.

Keywords: PACS; 72.20; 78.66; 73.50J; 61.16CSemiconductor; Electrical properties; Thin films; Indium oxide; Tungsten; Optical materials and properties

Catalytic reduction of NO in the presence of benzene on a Pt(332) surface by Yuhai Hu; Keith Griffiths (pp. 1666-1675).

The catalytic reduction of NO in the presence of benzene on the surface of Pt(332) has been studied using Fourier transform infra red reflection-absorption spectroscopy (FTIR-RAS) and thermal desorption spectroscopy (TDS). IR spectra show that while the presence of benzene molecules at low coverage (e.g., following an exposure of just 0.25L) promotes NO–Pt interaction, the adsorption of NO on Pt(332) at higher benzene coverages is suppressed. It is also shown that there are no strong interactions between the adsorbed NO molecules and the benzene itself or benzene-derived hydrocarbons, which can lead to the formation of intermediate species that are essential for N₂ production.TDS results show that the adsorbed benzene molecules undergo dehydrogenation accompanied by hydrogen desorption starting at 300K and achieving a maximum at 394K. Subsequent dehydrogenation of the benzene-derived hydrocarbons then begins with hydrogen desorption starting at 500K. N₂ desorption from NO adlayers on clean Pt(332) surface becomes significant at temperatures higher than 400K, giving rise to a peak at 465K. This peak corresponds to N₂ desorption from NO dissociation on step sites. The presence of benzene promotes N₂ desorption, depending on the benzene coverage. When the benzene exposure is 0.25L, the N₂ desorption peak at 459K is dramatically increased. Increasing benzene coverage also results in the intensification of N₂ desorption at ∼410K. At benzene exposures of 2.4L, N₂ desorption develops as a broad peak with a maximum at ∼439K.It is concluded that the catalytic reduction of NO by platinum in the presence of benzene proceeds by NO decomposition and subsequent oxygen removal at temperatures lower than 500K, and NO dissociation is a rate-limiting step. The contribution of benzene to N₂ desorption is mainly attributed to providing a source of H, which quickly reacts with NO-derived atomic O, leaving the surface with more vacant sites for further NO dissociation.

Keywords: NO; Platinum; Benzene; deNOx; Hydrocarbon; Selective catalytic reduction

AFM images of G₁-phase premature condensed chromosomes: Evidence for 30nm changed to 50nm chromatin fibers by Yihui Fan; Renfang Mao; Jing Bai; Xiaohong Zhang; Qingquan Lei; Songbin Fu (pp. 1676-1683).

To gain evidence for 30nm changed to 50nm chromatin fibers, we used atomic force microscopy (AFM) to study the ultrastructural organization of G₁-phase premature condensed chromosomes (PCC). The surface of early G₁-phase PCC is smooth and fibrous structures exist around the chromatids. The height of early G₁-phase PCC is about 410nm and the width is 1.07±0.11μm ( n=30). At late G₁-phase, the surface becomes globular. The height of late G1-phase PCC is about 370nm and the width is 845.04±82.84nm ( n=30). Phase image reveals that early G₁-phase PCC is composed of 50nm (48.91±6.63nm, n=30) chromatin fibers and these 50nm chromatin fibers tangle together, while late G₁-phase PCC is composed of 30nm (30.96±4.07nm, n=30) chromatin fibers. At high magnification, fibers existing around the chromatids become clear in early G₁-phase PCC. Chromatin fibers revealed by closer view of the end of chromatid are about 50nm. In late G₁-phase PCC, the surface presents globular structures. The shape of these globular structures is regular and the diameter is 118.96±11.70nm ( n=30). Our results clearly show that 30nm chromatin fibers change to 50nm chromatin fibers in G₁-phase PCC and suggest that 50nm chromatin fibers are the basic component of the mitotic chromosomes.

Keywords: Premature condensed chromosomes (PCC); Atomic force microscopy (AFM); 50; nm Chromatin fibers; 30; nm Chromatin fibers

Micro-patterns of Au@SiO₂ core-shell nanoparticles formed by electrostatic interactions by Youli Qi; Miao Chen; Shan Liang; Wu Yang; Jing Zhao (pp. 1684-1690).

In this paper, silica-coated Au nanoparticles (Au@SiO₂) were prepared by the technique of vortex mixing. Subsequently, these monodisperse Au@SiO₂ nanoparticles were functionalized by the silane reagents 3-aminopropyltriethoxysilane (APS) and 3-mercaptopropyltriethoxysilane (MPTS) respectively. Then, these NH₂-terminated and SO₃²⁻-terminated Au@SiO₂ nanoparticles were respectively assembled onto the substrates, which have been patterned with different self-assembly monolayers (SAMs), to form close-packed two-dimensional Au@SiO₂ nanoparticle arrays by electrostatic interactions. The morphologies and the optical properties of Au@SiO₂ nanoparticles with different silica-shell thicknesses were characterized by TEM and UV–vis. The compositions and zeta potentials of the functionalized Au@SiO₂ nanoparticles were examined by X-ray photoelectron spectroscopy (XPS) and dynamic light scattering (DLS). The morphologies of the patterns formed on different templates were characterized by atomic force microscopy (AFM).

Keywords: Core-shell; Au@SiO; ₂; nanoparticles; Surface functionalization; Electrostatic assembly; Micro-pattern

Structural characterization of nickel–titanium film on silicon carbide by Petr Macháč; Bohumil Barda; Jaroslav Maixner (pp. 1691-1693).

The presented work describes behavior of contact structures of Ni/Ti type on 6H–SiC n-type. The best contact resistivity obtained is 3.3×10⁻⁴Ωcm². The structure showed excellent thermal stability, it was stable after being tested for 10h at 900°C. XRD analysis after annealing at 960°C revealed orthorhombic Ni₂Si as the dominate phase.

Keywords: PACS; 73.40.Cg; 73.40.NsSiC; Ohmic contact; Nickel; Titanium; XRD analysis

Spectroscopic ellipsometric characterization of TiAlN/TiAlON/Si₃N₄ tandem absorber for solar selective applications by A. Biswas; D. Bhattacharyya; H.C. Barshilia; N. Selvakumar; K.S. Rajam (pp. 1694-1699).

Sputter deposited TiAlN/TiAlON/Si₃N₄ tandem absorber has been characterized by spectroscopic ellipsometry in the wavelength range of 450–1200nm. Each layer of the tandem absorber viz., TiAlN, TiAlON and Si₃N₄ has been deposited separately on copper substrate (Cu) and ellipsometric measurements have been carried out on each of these layers. The measured ellipsometric spectra were fitted with theoretically simulated spectra and the sample structure and wavelength dispersion of optical constants of each layers have been determined. The ellipsometric measurements have also been carried out on the three-layer tandem absorber deposited on Cu substrate. By analyzing the ellipsometric data, depth profiling of the tandem absorber has been carried out using the derived optical constants of the individual layers.

Keywords: Solar selective coating; Ellipsometry

Preparation of carbon nanosheets deposited on carbon nanotubes by microwave plasma-enhanced chemical vapor deposition method by Leyong Zeng; Da Lei; Weibiao Wang; Jingqiu Liang; Zhiqian Wang; Ning Yao; Binglin Zhang (pp. 1700-1704).

Carbon nanosheets were synthesized by microwave plasma-enhanced chemical vapor deposition method on carbon nanotubes substrate which was treated by hydrogen plasma. The results showed that the diameters of carbon nanotubes first got thick and then “petal-like” carbon nanosheets were grown on the outer wall of carbon nanotubes. The diameters of carbon nanotubes without and with carbon nanosheets were 100–150 and 300–500nm, respectively. Raman spectrum indicated the graphite structure of carbon nanotubes/carbon nanosheets. The hydrogen plasma treatment and reaction time greatly affected the growth and density of carbon nanosheets. Based on above results, carbon nanosheets/carbon nanotubes probably have important applications as cold cathode materials and electrode materials.

Keywords: Carbon nanotubes; Carbon nanosheets; Chemical vapor deposition

The synthesis and kinetic growth of anisotropic silver particles loaded on TiO₂ surface by photoelectrochemical reduction method by Xin He; Xiujian Zhao; Baoshun Liu (pp. 1705-1709).

Silver nanorods with average diameters of 120–230nm and aspect ratio of 1.7–5.0 were deposited on the surface of TiO₂ films by photoelectrochemical reduction of Ag⁺ to Ag under UV light. The composite films prepared on soda-lime glass substrates were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results show that the TiO₂ film after UV irradiation in AgNO₃ solution is composed of anatase phase TiO₂ and metallic silver with face centered cubic structure. Other compounds cannot be found in the final films. The maximum deposition content of silver particles on the surface of TiO₂ film was obtained with the AgNO₃ concentration of 0.1M. The kinetic growth rates of silver particles can be controlled by photocatalytic activity of TiO₂ films. The studies suggest that the growth rates of silver particles increase with the enhancement of photocatalytic activity of TiO₂ films. The maximum growth rate of silver particles loaded on TiO₂ films can be up to 0.353nmmin⁻¹ among samples 1#, 2# and 3#, while the corresponding apparent rate constant of TiO₂ is 1.751×10⁻³min⁻¹.

Keywords: Photoelectrochemical reduction; Photocatalytic activity; Anisotropic silver particles; Ag–TiO; ₂; composite films

Surface nano/micro functionalization of PMMA thin films by157nm irradiation for sensing applications by E. Sarantopoulou; Z. Kollia; A.C. Cefalas; K. Manoli; M. Sanopoulou; D. Goustouridis; S. Chatzandroulis; I. Raptis (pp. 1710-1719).

Laser irradiation at 157nm of polymethylmethacrylate (PMMA) thin films induces major variations of polymer film thicknesses from sorption (absorption/desorption) of methanol and ethanol analytes in the gas phase as much as 400%, in comparison to the film thickness variation of the non-irradiated areas. The structural changes of irradiated areas involve scission of polymeric chains, cross-linking and formation of new bonds. In addition, 157nm induces surface and volume morphological changes in the nano/micro domain, with different shapes, depending on the irradiation conditions. The reversibility of the sorption processes suggests that the polymer swelling has its origin at the tendency of the system to increase its volume during sorption. The internal forces from sorption are higher than the weak dipole interactions between the polymer and the analytes and they are amplified following 157nm irradiation. A simple qualitative model explains adequately the experimental results. 157nm laser treatment forms the basis to engineer a novel class of polymer sensor arrays with enhanced detection efficiency of liquid/gas analytes.

Keywords: PACS; 68.47.Mn; 81.65.−b; 61.80.Ba; 07.07.DfPMMA; Swelling; VUV polymer surface treatment; Polymer sensor; Sorption; Surface modification; Hydrophobic

HREELS study of the adsorption and evolution of diethylamine (DEA) on Si(100) surfaces by S. Yeninas; A. Brickman; J.H. Craig Jr.; J. Lozano (pp. 1720-1724).

The adsorption of diethylamine (DEA) on Si(100) at 100K was investigated using high-resolution electron energy loss spectroscopy (HREELS) and electron stimulated desorption (ESD). The thermal evolution of DEA on Si(100) was studied using temperature programmed desorption (TPD). Our results demonstrate DEA bonds datively to the Si(100) surface with no dissociation at 100K. Thermal desorption of DEA takes place via a β-hydride elimination process leaving virtually no carbon behind. Electronic processing of DEA/Si(100) at 100K results in desorption of ethyl groups; however, carbon and nitrogen are deposited on the surface as a result of electron irradiation. Thermal removal of carbon and nitrogen was not possible, indicating the formation of silicon carbide and silicon nitride.

Keywords: PACS; 68.47.Fg; 68.43.Rs; 79.20.La; 68.43.PqDiethylamine; ESD; HREELS; TPD; Si(1; 0; 0); Adsorption

Investigation of monolayer dispersion of MoO₃ supported on titanate nanotubes by Wei Wang; Jingwei Zhang; Huizhong Huang; Zhishen Wu; Zhijun Zhang (pp. 1725-1729).

The monolayer dispersion of MoO₃ supported on the surface of titanate nanotubes (TNT) were prepared by heating mechanical mixture of molybdate (HMA) and TNT. The result shows that MoO₃ can disperse spontaneously onto the surface of TNT, and the dispersion capacity is ca. 27mgMoO₃/g TNT by X-ray diffraction (XRD). On the basis of thermogravimetric (TG) and X-ray photoelectron spectroscopy (XPS) analysis, it was found that the HMA as precursor could not decompose completely into MoO₃ crystal on the surface of TNT around the threshold above decomposed temperature due to the strong interaction between HMA and the surface of TNT.

Keywords: Monolayer dispersion; Titanate nanotube; MoO; ₃; XPS

Structure, morphology and optical properties of SiO2−_x thin films prepared by plasma-assisted pulsed laser deposition by Xiliang He; Jiehua Wu; Lingnan Wu; Lili Zhao; Xiangdong Gao; Xiaomin Li (pp. 1730-1735).

The amorphous silicon oxide SiO2−_x thin films were prepared by the plasma-assisted pulsed laser deposition (PLD) method. X-ray diffraction spectrometry (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-VIS-NIR scanning spectrophotometry and ellipsometry were used to characterize the crystallinity, microscopic morphology and optical properties of obtained thin films. The influences of substrate temperatures, oxygen partial pressures and oxygen plasma assistance on the compositions of silicon oxide (SiO2−_x) thin films were investigated. Results show that the deposited thin films are amorphous and have high surface quality. Stoichiometric silicon dioxide (SiO₂) thin film can be obtained at elevated temperature of 200°C in an oxygen plasma-assisted atmosphere. Using normal incidence transmittance, a novel and simple method has been proposed to evaluate the value of x in transparent SiO2−_x thin films on a non-absorbing flat substrate.

Keywords: Pulsed laser deposition; Plasma assistance; Silicon oxide; Thin films; Optical properties

A silane pre-treatment for improving corrosion resistance performances of emeraldine base-coated aluminium samples in neutral environment by Laura Cecchetto; Alain Denoyelle; Didier Delabouglise; Jean-Pierre Petit (pp. 1736-1743).

An aluminium–magnesium alloy AA5182 substrate pre-treated with a 3-aminopropyl-triethoxysilane (APS)-based solution and coated with emeraldine base (EB) showed improved corrosion resistance to neutral salt spray test, compared to samples pre-treated with phosphoric acid-based solutions prior to the EB coating. Scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX) characterisations of samples pre-treated with APS showed the presence of an uneven silane coating on the aluminium surface according to the surface microstructure. The potentiodynamic study performed on the EB-coated samples showed a noticeable reduction of corrosion current of coupons pre-treated with APS, while no relevant difference in corrosion behaviour was observed between APS and phosphoric acid pre-treated samples prior to the EB coating. The coupling activity of APS between the AA5182 surface and EB coating at the most sensitive corrosion sites could be responsible of an improved adhesion of the EB coating at these points and could explain the observed improved corrosion resistance.

Keywords: PACS; 81.65.KnCorrosion protection; Aluminium; Polyaniline; Silane; Adhesion

On the use of response surface methodology to predict and interpret the preferred c-axis orientation of sputtered AlN thin films by J. Adamczyk; N. Horny; A. Tricoteaux; P.-Y. Jouan; M. Zadam (pp. 1744-1750).

This paper deals with experimental design applied to response surface methodology (RSM) in order to determine the influence of the discharge conditions on preferred c-axis orientation of sputtered AlN thin films. The thin films have been deposited by DC reactive magnetron sputtering on Si (100) substrates. The preferred orientation was evaluated using a conventional Bragg-Brentano X-ray diffractometer ( θ–2 θ) with the CuKα radiation. We have first determined the experimental domain for 3 parameters: sputtering pressure (2–6mTorr), discharge current (312–438mA) and nitrogen percentage (17–33%). For the setup of the experimental design we have used a three factors Doehlert matrix which allows the use of the statistical response surface methodology (RSM) in a spherical domain. A four dimensional surface response, which represents the (0002) peak height as a function of sputtering pressure, discharge current and nitrogen percentage, was obtained. It has been found that the main interaction affecting the preferential c-axis orientation was the pressure-nitrogen percentage interaction. It has been proved that a Box-Cox transformation is a very useful method to interpret and discuss the experimental results and leads to predictions in good agreement with experiments.

Keywords: Aluminium nitride; Reactive DC sputtering; Response surface methodology; X-ray diffraction

Enhancing the properties of wood through chemical modification with palmitoyl chloride by Gowdra K. Prakash; Kittappa M. Mahadevan (pp. 1751-1756).

Hevea brassiliensis (rubber wood) was esterified with palmitoyl chloride, prepared from the reaction of palmitic acid with thionyl chloride. The weight gain of the wood increased with increasing reaction time and temperature, the esterified wood were evaluated for their photostability and dimensional stability. Fourier transform infrared spectroscopy (FTIR), solid-state cross-polarization/magic angle spinning¹³C nuclear magnetic resonance spectroscopy (CP/MAS¹³C NMR) were used to elucidate the characteristics of wood after esterification. The dimensional stability and photostability of the wood was improved by esterification. This is an important observation since chemical modification of wood with fatty acid chlorides has been found to induce thermo-plasticity into wood.

Keywords: Chemical modification; Dimensional stability; Photodegradation; Wood; Hevea brassiliensis; Palmitoyl chloride; FTIR; ¹³; C NMR

Effects of microwave plasma treatment on the field emission properties of printed carbon nanotubes/Ag nano-particles films by Yuxiang Qin; Ming Hu (pp. 1757-1762).

The effects of Ar microwave plasma treatment on field emission properties of the printed carbon nanotubes (CNTs) cathode films using Ag nano-particles as binder were investigated. The field emission J– E characteristics were measured at varied plasma treatment time. Significant improvement in emission current density, emission stability and uniformity were achieved for the Ar treated CNTs films, even though the plasma treatment increased the turn on electric field slightly. High-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy revealed the microstructural changes of CNTs after the plasma treatment. The improved field emission properties of CNTs film can be attributed to the generation of a high density of structural defects after treatment, which increased greatly the possible emission active sites. Besides, the formation of the sharpened and open-ended CNTs tips is all helpful for improving the field emission properties of the treated CNTs.

Keywords: JEL classification; 79.70.+q; 73.63.Fg; 52.77.BnCarbon nanotubes; Field emission; Plasma treatment; Ag nano-particles

Enrichment of poly(methyl methacrylate) and its graft copolymer of polybutadiene on the surface of polypropylene blends by Han Jia Chen; Xu Hua Shi; Ya Fei Zhu; Yi Zhang; Jia Rui Xu (pp. 1763-1770).

Poly(methyl methacrylate) (PMMA) and its graft copolymer of polybutadiene were used as the macromolecular surface modifiers of polypropylene. The enrichment and diffusion of the modifiers onto the surface of polypropylene blends were investigated using FTIR-ATR, CDA and SEM. It has been found that the selective aggregation of the modifier component on the surface of polypropylene was mainly affected by the content, molecular weight and size of the segregated domains. Lower content and higher surface energy die were in favor of the enrichment of the additive. PMMA with higher molecular weight showed larger domain phase and lower diffusion velocity which resulted in less enrichment on the surface of PP blends.

Keywords: Polypropylene; Poly(methyl methacrylate); Surface enrichment; Selective aggregation; Polybutadiene graft copolymer

Low temperature deposition of TiO₂ thin films on polyvinyl alcohol fibers with photocatalytical and antibacterial activities by Zhang Liuxue; Wang Xiulian; Liu Peng; Su Zhixing (pp. 1771-1774).

Fine particles of photoactive anatase-type TiO₂ coated polyvinyl alcohol (PVA) fibers (TiO₂/PVA) were prepared successfully via a simple dip-coating method. Tetrabutyl orthotitanate (TBOT) was hydrolyzed in presence of hydrolysis control agent tetrabutylammonium hydroxide (TBA)OH and the TiO₂ fine particles were crystallized under microwave (MW) irradiation. The X-ray diffraction (XRD) and selected-area electron diffraction (SAED) analyses indicated that the fine particles obtained with MW irradiation have much higher crystallinity with a single phase anatase compared with the non-MW-treated solution. The continuous layers of titania were found on PVA fibers by the scanning electron microscopy (SEM) analysis. The fibers with anatase coatings showed high photocatalytic property on the photodegradation of methylene blue (MB) and high antibacterial activity.

Keywords: PACS; 68.37.−d; 78.66.−wMicrowave irradiation; Nanocrystalline titania; Thin film; PVA fibers; Antibacterial activity; Photocatalytical activity

Chemical treatment of TiO₂-based coatings formed by plasma electrolytic oxidation in electrolyte containing nano-HA, calcium salts and phosphates for biomedical applications by Daqing Wei; Yu Zhou; Dechang Jia; Yaming Wang (pp. 1775-1782).

TiO₂-based coatings were formed on titanium alloy by plasma electrolytic oxidation (PEO) in an electrolyte containing nano-HA, calcium salts and phosphates. Bioactive surface was formed after chemical treatment (NaOH aqueous solution) of the PEO coating. The surface of the PEO coating was mainly composed of Ti, O, Ca and P showing anatase and rutile; while that of the chemically treated PEO (CT-PEO) coating mainly contains Ti, O, Ca and Na showing anatase, rutile and amorphous phase. And the chemically treated surface exhibits dissolution of P and introduction of Na during the chemical treatment process. The chemical treatment has no effect on the chemical states of Ca and Ti of the PEO coating. In addition, the surface constituents of the CT-PEO coating show a uniform distribution near its surface with increasing depth. When incubated in a simulated body fluid for 7 and 14 days, the PEO coating does not exhibit apatite-forming ability; however, apatite was successfully deposited on the CT-PEO coating after 7 days probably due to the formation of hydroxyl functionalized surface, enhancing the heterogeneous nucleation of apatite. The addition of nano-HA in the electrolyte has effects on the surface character and apatite-forming ability of the PEO coating; however, it has no obvious influence on those of the CT-PEO coatings.

Keywords: Coating; Titania; Titanium alloy; Plasma electrolytic oxidation; Chemical treatment

Characterization of LaF₃ coatings prepared at different temperatures and rates by Hua Yu; Yanming Shen; Yun Cui; Hongji Qi; JianDa Shao; ZhengXiu Fan (pp. 1783-1788).

LaF₃ thin films were prepared by thermal boat evaporation at different substrate temperatures and various deposition rates. X-ray diffraction (XRD), Lambda 900 spectrophotometer and X-ray photoelectron spectroscopy (XPS) were employed to study crystal structure, transmittance and chemical composition of the coatings, respectively. Laser-induce damage threshold (LIDT) was determined by a tripled Nd:YAG laser system with a pulse width of 8ns. It is found that the crystal structure became more perfect and the refractive index increased gradually with the temperature rising. The LIDT was comparatively high at high temperature. In the other hand, the crystallization status also became better and the refractive index increased when the deposition rate enhanced at a low level. If the rate was super rapid, the crystallization worsened instead and the refractive index would lessen greatly. On the whole, the LIDT decreased with increasing rate.

Keywords: PACS; 68.37.Yz; 78.20.Ci; 79.20.DsLaF; ₃; film; Substrate temperature; Deposition rate; LIDT

Interfacial modification of silica surfaces through γ-isocyanatopropyl triethoxy silane–amine coupling reactions by Brandon M. Vogel; Dean M. DeLongchamp; Christine M. Mahoney; Leah A. Lucas; Daniel A. Fischer; Eric K. Lin (pp. 1789-1796).

The development of robust, cost-effective methods to modify surfaces and interfaces without the specialized synthesis of unique coupling agents could provide readily accessible routes to optimize and tailor interfacial properties. We demonstrate that γ-isocyanatopropyl triethoxysilane (ISO) provides a convenient route to functionalize silica surfaces through coupling reactions with readily available reagents. ISO coupling agents layers (CALs) can be prepared from toluene with triethylamine (TEA), but the coupling reaction of an amine to the ISO CAL does not proceed. We use near edge X-ray absorption fine structure (NEXAFS), time-of-flight secondary ion mass spectrometry (TOF-SIMS) and sessile drop contact angle to demonstrate the isocyanate layer is not degraded under coupling conditions. Access to silanes with chemical functionality is possible with ISO by performing the coupling reaction in solution and then depositing the product onto the surface. Two model CAL surfaces are prepared to demonstrate the ease and robust nature of this procedure. The surfaces prepared using this method are the ISO reacted with octadecylamine to produce a hydrocarbon surface of similar quality to octadecyl trichlorosilane (OTS) CALs and with 9-aminofluorene (AFL), an aromatic amine functionality whose silane is otherwise unavailable commercially.

Keywords: Surface modification; Isocyanate; Silane; Near edge X-ray absorption fine structure spectroscopy; Time of flight secondary ion mass spectrometry

Sliding behavior of water droplets on line-patterned hydrophobic surfaces by Shunsuke Suzuki; Akira Nakajima; Kouichi Tanaka; Munetoshi Sakai; Ayako Hashimoto; Naoya Yoshida; Yoshikazu Kameshima; Kiyoshi Okada (pp. 1797-1805).

We prepared line-patterned hydrophobic surfaces using fluoroalkylsilane (FAS) and octadecyltrimethoxysilane (ODS) then investigated the effect of line direction on sliding behavior of water droplets by direct observation of the actual droplet motion during sliding. Water droplets slide down with a periodic large deformation of the contact line and sliding velocity fluctuation that occurred when they crossed over the 500-μm ODS line regions in FAS regions on a Si surface tilted at 35°. These behaviors are less marked for motion on a 100-μm line surface, or on lines oriented parallel to the slope direction. Smaller droplets slide down with greater displacement in the line direction on 500-μm line patterning when the lines were rotated at 13° in-plane for the slope direction. This sliding behavior depended on the droplet size and rotation angle, and is accountable by the balance between gravitational and retentive forces.

Keywords: PACS; Surface patterning; 81.65.Cf; In liquid–solid interfaces; 68.08.Bc; Photolithography; 85.40.HpWetting; Silane; Hydrophobicity; Coatings; Surface patterning; Photolithography

Composition and corrosion resistance of cerium conversion films on the AZ31 magnesium alloy and its relation to the salt anion by M.F. Montemor; A.M. Simões; M.G.S. Ferreira; M.J. Carmezim (pp. 1806-1814).

Pre-treatments based on different cerium salts were applied to the AZ31 Mg alloy. The pre-treatments were performed by immersion in solutions of various Ce(III) salts: cerium chloride, cerium nitrate, cerium sulphate and cerium phosphate. The chemical composition of the treated surfaces was investigated by X-ray photoelectron spectroscopy and Auger electron spectroscopy, whereas the corrosion behaviour of the pre-treated AZ31 substrates was investigated in 0.005M NaCl solutions using potentiodynamic polarisation and open circuit potential monitoring. The surface film contained a mixture of Ce(IV) and Ce(III) salts. The film thickness depends upon the cerium salt used. The electrochemical results show that all the conversion pre-treatments reduced the corrosion activity of the AZ31 Mg alloy substrates in the presence of chloride ions. The corrosion protection efficiency is related with the anion present in the cerium salt.

Keywords: Magnesium; Cerium; XPS; AES; Corrosion

Long-distance oxygen plasma sterilization: Effects and mechanisms by Hongxia Liu; Jierong Chen; Liqing Yang; Yuan Zhou (pp. 1815-1821).

The distribution of electrons, ions and oxygen radicals in long-distance oxygen plasma and the germicidal effect (GE) of Escherichia coli on the surface of medical poly(tetrafluoroethylene) (PTFE) film were studied. The quantity of protein leakage and the production of lipid peroxide in bacterial suspension as well as the state of DNA were measured after sterilization to analyse the inactivation mechanisms. The results showed that the concentration of electrons and ions decreased rapidly with increasing the distance from the center of induction coil, which approximated to 0 at 30cm, whereas the concentration of oxygen radicals reduced slowly, i.e. decreased 30% within 40cm. GE value reached 3.42 in the active discharge zone (0cm) and exceeded 3.32 within 40cm when plasma treatment parameters were set as follows: plasma rf power at 100W, treatment time at 60s and oxygen flux at 40cm³/min. Fast etching action on cell membrane by electrons, ions and attacking polyunsaturation fatty acid (PUFA) in cell membrane by oxygen radicals are primary reasons of oxygen plasma sterilization in the active discharge and the afterglow zone, respectively. The GE of UV radiation in long-distance oxygen plasma is feebleness.

Keywords: PACS; 52.77. −jRemote oxygen plasma; Poly(tetrafluoroethylene); Escherichia coli; Sterilization

Optical channel waveguides with trapezoidal-shaped cross sections in KTiOPO₄ crystal fabricated by ion implantation by Feng Chen; Yang Tan; Lei Wang; Dong-Chao Hou; Qing-Ming Lu (pp. 1822-1824).

Optical channel waveguides were fabricated in KTiOPO₄ crystal by He⁺-ion implantation using photoresist masks with wedged-shaped cross sections. Semi-closed barrier walls with reduced refractive indices inside the crystal constructed the enclosed regions to be channel waveguides with trapezoidal-shaped cross sections. The m-line as well as end-fire coupling arrangements were performed to characterize the waveguides with light at wavelength of 632.8nm. The propagation loss of the channel waveguides was determined to be as low as ∼2dB/cm after simple post-irradiation thermal annealing treatment in air.

Keywords: PACS; 42.82.Et; 85.40.Ry; 42.70.MpChannel waveguides; Ion implantation; KTiOPO; ₄; crystal

Enhancement of photocatalytic degradation of polyethylene plastic with CuPc modified TiO₂ photocatalyst under solar light irradiation by Xu Zhao; Zongwei Li; Yi Chen; Liyi Shi; Yongfa Zhu (pp. 1825-1829).

Solid-phase photocatalytic degradation of polyethylene (PE) plastic, one of the most common commercial plastic, over copper phthalocyanine (CuPc) modified TiO₂ (TiO₂/CuPc) photocatalyst was investigated in the ambient air under solar light irradiation. Higher PE weight loss rate, greater texture change; more amount of generated CO₂, which is the main product of the photocatalytic degradation of the composite PEC plastic can be achieved in the system of PE–(TiO₂/CuPc) in comparison with PE–TiO₂ system. The CuPc promoted charge separation of TiO₂ and enhanced the photocatalytic degradation of PE based on the analysis of surface photovoltage spectroscopy (SPS). During the photodegradation of PE plastic, the reactive oxygen species generated on TiO₂ or TiO₂/CuPc particle surfaces play important roles. The present study demonstrates that the combination of polymer plastic with TiO₂/CuPc composite photocatalyst in the form of thin film is a practical and useful way to photodegrade plastic contaminants under solar light irradiation.

Keywords: Photocatalytic degradation; Polyethylene; Plastic; CuPc; TiO; ₂

Electron beam treatments of electrophoretic ceramic coatings by M.F. De Riccardis; D. Carbone; E. Piscopiello; M. Vittori Antisari (pp. 1830-1836).

In this work a method to densify ceramic coating obtained by electrophoresis and to improve its adhesion to the substrate is proposed. It consists in irradiating the coating surface by electron beam (EB). Alumina and alumina–zirconia coatings were deposited on stainless steel substrates and treated by low power EB. SEM, XRD and TEM characterizations demonstrated that the sintering occurred. Moreover, it is shown that on alumina–zirconia coating the EB irradiation produced a composite material consisting principally of tetragonal zirconia particles immersed in an amorphous alumina matrix. The adhesion stress of EB treated coating was estimated by stud pull test and it was found to be comparable to that of plasma-sprayed coatings.

Keywords: PACS; 81.05.Je; 81.40.−zAlumina; Zirconia; EPD; Electron beam; Microstructure; Adhesion stress

Surface analysis of thermally annealed porous silicon by M. Banerjee; E. Bontempi; A.K. Tyagi; S. Basu; H. Saha (pp. 1837-1841).

Quasi-monocrystalline porous silicon (QMPS) has high potential for photovoltaic application for its enhanced optical absorption compared to bulk silicon in the visible range of solar spectrum. In this study, QMPS was formed from low porosity (∼20–30%) porous silicon (PS) produced by electrochemical anodization, and thermal annealing in the temperature range 1050–1100°C under pure hydrogen ambient for a duration of 30min. We analyzed the material surface by grazing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and dynamic secondary ion mass spectroscopy (SIMS) study. The crystallinity was confirmed by GIXRD while FESEM studies revealed that the surface layer is pore free with voids embedded inside the body. AFM studies indicated relatively smooth and uniform surface and the dynamic SIMS study showed the depth profiles of impurities present in the material.

Keywords: Porous silicon; Thermal annealing; Surface analysis

Modification of H-terminated Ge surface in hydrochloric acid by Kibyung Park; Younghwan Lee; Sangwoo Lim (pp. 1842-1846).

Various amounts of H-termination on a Ge surface were prepared by dipping a Ge wafer in differentially diluted hydrofluoric acid solutions for different periods of time. Formation of GeH_x in hydrofluoric acid and its disappearance in hydrochloric acid (HCl) were directly measured by using multiple internal reflection Fourier transform infrared spectroscopy (MIR FT-IR). Peak intensity of GeH_x vibration mode was increased with diluted hydrofluoric acid (DHF) treatment time and the concentration of HF solution. Therefore, it is suggested that microroughness of a Ge surface changes depending on the concentration of HF. Peak intensity of GeH_x vibration mode was reduced when the GeH_x surface was treated in HCl solution. With an increase in HCl treatment time, peak intensity of GeH_x vibration mode was reduced. Ge surfaces treated in a more diluted HF solution were barely modified, because it was thought to have fewer kink sites, dihydrides and trihydrides.

Keywords: PACS; 33.20.EaGermanium; Surface termination; Surface roughness; FT-IR

Synthesis, microstructure and photoluminescence of Eu³⁺/Tb³⁺ activated Y₂SiO₅ nanophosphors by new silicate sources by Lei Zhou; Bing Yan (pp. 1847-1851).

Y2−_xTb_xSiO₅ and Y2−_xEu_xSiO₅ nanophosphors with seven different kinds of silicate sources were synthesized by sol–gel method. The structures have been investigated to be composed of nanometer-size grains of 30–60nm through X-ray diffraction (XRD) and scanning electron microscopy (SEM) was used to compare the different morphology of patterns from seven different silicon sources. The photoluminescence of Y2−_xTb_xSiO₅ was investigated as a function of silicate sources and the results revealed that these nanometer materials showed the characteristic emission⁵D₄→⁷F_J ( J=6, 5, 4, 3) of Tb ions. The characteristic emission⁵D₀→⁷F_J ( J=1, 2, 4) of Eu ions was also found in the materials of Y2−_xEu_xSiO₅.

Keywords: PACS; 78.20.−e; 78.55.−mRare earth silicate; Nanophosphors; Photoluminescence; Microstructure; New silica source precursors; Sol–gel synthesis

Electrical properties and dielectric relaxation of thermally evaporated zinc phthalocyanine thin films by H.M. Zeyada; M.M. El-Nahass (pp. 1852-1858).

The electrical transport properties and dielectric relaxation of Au/zinc phthalocyanine, ZnPC/Au devices have been investigated. The DC thermal activation energy at temperature region 400–500K is 0.78eV. The dominant conduction mechanisms in the device are ohmic conduction below 1V and space charge limited conduction dominated by exponential trap distribution in potentials >1V. Some parameters, such as concentration of thermally generated holes in valence band, the trap concentration per unit energy range at the valence band edge, the total concentration of traps and the temperature parameter characterizing the exponential trap distribution and their relation with temperatures have been determined. The AC electrical conductivity, σ_ac, as a function of temperature and frequency has been investigated. It showed a frequency and temperature dependence of AC conductivity for films in the temperature range 300–400K. The films conductivity in the temperature range 400–435K increased with increasing temperature and it shows no response for frequency change. The dominant conduction mechanism is the correlated barrier hopping. The temperature and frequency dependence of real and imaginary dielectric constants and loss tangent were investigated.

Keywords: PACS; 73.50.−hZnPc thin films; Electrical and dielectric properties

A statistical evaluation of the field emission for copper oxide nanostructures by M.S.F. da Rocha; T.E.A. Santos; A.C. de Paulo; V.R. Hering; Daniel den Engelsen; J.H. Vuolo; S.S. Mammana; V.P. Mammana (pp. 1859-1869).

A statistical data analysis methodology was developed to evaluate the field emission properties of many samples of copper oxide nanostructured field emitters. This analysis was largely done in terms of Seppen–Katamuki (SK) charts, field strength and emission current. Some physical and mathematical models were derived to describe the effect of small electric field perturbations in the Fowler–Nordheim (F–N) equation, and then to explain the trend of the data represented in the SK charts. The field enhancement factor and the emission area parameters showed to be very sensitive to variations in the electric field for most of the samples. We have found that the anode–cathode distance is critical in the field emission characterization of samples having a non-rigid nanostructure.

Keywords: PACS; 85.60.Pg; 85.45.Fd; 83.85.Ns; 82.45.Aa; 81.16.Be; 81.07.Bc; 79.70.+q; 68.37Vj; 61.46.+wField emission; Copper oxide nanostructures; Fowler–Nordheim; Seppen–Katamuki; Statistical method; Computational analysis

Further investigation on the formation mechanisms of (NH₄)₂SiF₆ synthesized by dry etching technique by I. Kabacelik; B. Ulug (pp. 1870-1873).

The validity of two formation mechanisms of ammonium silicofluoride (ASF), which are proposed to take place when a silicon surface is exposed to the vapor of HNO₃/HF acid mixture is investigated. Of the two proposed mechanisms regarding the synthesis of ASF on silicon surface, validity of the first predicting the release of hydrofluosilicic acid (H₂SiF₆) at the intermediate stage is examined by FTIR spectroscopy and the second mechanism suggesting O₂ release is investigated using the Winkler technique. IR absorbance bands of SiF₆²⁺ are observed on the fresh samples prepared at low (1/100) HNO₃/HF volume fractions. No significant amount of oxygen is detected during the synthesis of ASF films on silicon surface by dry etching technique. These two observations together provide firmer support for the validity of the second mechanism.

Keywords: PACS; 61.43.Gt; 68.47.Fg; 78.55.MbDry etching; Porous silicon; Ammonium silicofluoride; Oxygen; Hydrofluosilicic acid; FTIR

XPS characterization of sensitized n-TiO₂ thin films for dye-sensitized solar cell applications by Antonio Otávio T. Patrocínio; Eucler B. Paniago; Roberto M. Paniago; Neyde Y. Murakami Iha (pp. 1874-1879).

TiO₂ thin films, employed in dye-sensitized solar cells, were prepared by the sol–gel method or directly by Degussa P25 oxide and their surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The effect of adsorption of the cis-[Ru(dcbH₂)₂(NCS)₂] dye, N3, on the surface of films was investigated. From XPS spectra taken before and after argon-ion sputtering procedure, the surface composition of inner and outer layers of sensitized films was obtained and a preferential etching of Ru peak in relation to the Ti and N ones was identified. The photoelectrochemical parameters were also evaluated and rationalized in terms of the morphological characteristics of the films.

Keywords: TiO; ₂; Dye-sensitized solar cells; XPS; Sputtering

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Applied Surface Science (v.254, #6)

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Applied Surface Science (v.254, #6)