Applied Surface Science (v.254, #8)
Deposition of aluminum nitride thin film on Si(1 1 1) by KrF excimer laser and its characterizations by Ming Chang Shih; Chi Wei Liang; Ping Ju Chaing (2211-2215).
We present the deposition of aluminum nitride (AlN) thin film by KrF excimer laser sputtering and the study of the effects of substrate temperature and laser fluences. Deposition rate of AlN thin film at 0.3 Å/pulse has been achieved with laser fluence of 1500 mJ/cm2 and at substrate temperature of 250 K, and this shows the enhancement of the deposition rate at low substrate temperature. Surface morphology of the deposited films is characterized by atomic force microscopy (AFM). In addition, the electrical performance of the MIS devices with AlN thin films prepared in this experiment has been characterized.
Keywords: Pulse laser deposition; Aluminum nitrides; MIS devices;
Modification of anode surface in organic light-emitting diodes by chalcogenes by Marina A. Katkova; Vasilii A. Ilichev; Alexey N. Konev; Maxim A. Batenkin; Irina I. Pestova; Alexey G. Vitukhnovsky; Mikhail N. Bochkarev (2216-2219).
Influence of thin chalcogen X (S, Se, Te) interlayer between anode (indium–tin oxide, ITO) and a layer of N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD) used as a hole-transport layer (HTL) on the operating characteristics of organic light-emitting diodes (OLEDs) of composition ITO/X/TPD/Alq3/Yb (Alq3 – aluminum 8-quinolinolate) has been investigated. It was found that the sulphur layer decreases operating voltage and enhances operating stability of a device while the selenium or tellurium interlayers impair these characteristics.
Keywords: OLEDs; Sulphur; Selenium; Tellurium; ITO/TPD interface;
Compositional origin of surface roughness variations in air-annealed ZnO single crystals by D. Elizabeth Pugel; R.D. Vispute; S.S. Hullavarad; T. Venkatesan; B. Varughese (2220-2223).
We directly investigated the chemical compositional origin of surface roughness variations in air-annealed ZnO single crystal samples for annealing temperatures up to 1000 °C. Atomic Force Microscopy (AFM) showed temperature-dependent changes in surface roughness and morphology, with a maximum in surface roughness of 2 nm found for samples annealed at 400 °C. The O(1s) line, measured by X-ray Photoelectron Spectroscopy (XPS) showed a maximum for Zn(OH)2 and a minimum for off-stoichiometric ZnO at 400 °C; while the Zn(2p) peaks show an increase in slope at that temperature. These results indicate that the roughness arises from Zn diffusion and loss of surface oxygen.
Keywords: ZnO; Single crystal; Surface morphology; Air-annealing;
Chemical vapor deposition of Zr x Ti1−x O2 and Hf x Ti1−x O2 thin films using the composite anhydrous nitrate precursors by Qi Yue Shao; Ai Dong Li; Yan Dong; Feng Fang; Jian Qing Jiang; Zhi Guo Liu (2224-2228).
Zr–Ti and Hf–Ti composite nitrates were successfully developed as single-source precursors for the chemical vapor deposition (CVD) of Zr x Ti1−x O2 and Hf x Ti1−x O2 thin films. The Zr–Ti nitrate can be assumed as a solid solution of the individual Zr and Ti nitrates, and the Zr/Ti molar ratio in the deposited Zr x Ti1−x O2 films is consistent with that in the precursor. The Hf–Ti nitrate appears to be a mixture of the Hf and Ti nitrates and the composition of the deposited Hf x Ti1−x O2 films depends remarkably on the heating time of precursor. Both Zr x Ti1−x O2 and Hf x Ti1−x O2 films exhibit trade-off properties between band gap and dielectric constant. The obtained results suggest that Zr x Ti1−x O2 and Hf x Ti1−x O2 films are promising candidates for gate dielectric application to improve the scalability and reduce the leakage current of the future complementary metal-oxide-semiconductor (CMOS) devices.
Keywords: Zr x Ti1−x O2; Hf x Ti1−x O2; Gate dielectric; Anhydrous metal nitrate; Single-source precursor; CVD;
Fabrication of uniform porous alumina materials by radio frequency (RF) magnetron sputtering by YueFeng Tang; Jun Qi; ZhengBin Gu; ZhiPeng Huang; AiDong Li; YanFeng Chen (2229-2232).
Fabrication of porous materials with uniform pore size distribution remains a challenge. In this paper, a kind of uniform porous alumina material was fabricated on a template of polystyrene microspheres by radio frequency (RF) magnetron sputtering. Surface of samples was observed by scanning electron microscopy (SEM), and the phase of porous materials was confirmed by X-ray diffraction (XRD). The pore size distribution of samples was tested by mercury intrusion method.
Keywords: Uniform pore; Porous alumina materials; RF magnetron sputtering; Polystyrene template; Mercury intrusion method;
Effect of ambient hydrogen sulfide on the physical properties of vacuum evaporated thin films of zinc sulfide by Beer Pal Singh; Virendra Singh; R.C. Tyagi; T.P. Sharma (2233-2237).
Evaporated thin films of zinc sulfide (ZnS) have been deposited in a low ambient atmosphere of hydrogen sulfide (H2S ∼10−4 Torr). The H2S atmosphere was obtained by a controlled thermal decomposition of thiourea [CS(NH2)2] inside the vacuum chamber. It has been observed that at elevated substrates temperature of about 200 °C helps eject any sulfur atoms deposited due to thermal decomposition of ZnS during evaporation. The zinc ions promptly recombine with H2S to give better stoichiometry of the deposited films. Optical spectroscopy, X-ray diffraction patterns and scanning electron micrographs depict the better crystallites and uniformity of films deposited by this technique. These deposited films were found to be more adherent to the substrates and are pinhole free, which is a very vital factor in device fabrication.
Keywords: Zinc sulfide; Hydrogen sulfide; Evaporation; Optical properties; Structural properties;
A refined Ehrlich–Schwoebel effect on the modification of Si surface nanostructures by post ion milling by Jing Zhou; Wen-bin Fan; Wen-bin Chen; You-yuan Zhao; Ming Lu (2238-2243).
A modeling work has been conducted on a phenomenon called post ion milling (PIM), a post-treatment of Ar+ ion sputtering to modify nanostructures on solid surface. It was found by experiments that for PIM with a sufficiently low ion flux, both the average dot size and the surface roughness of Si nanodot arrays on Si(1 0 0) decline steadily against milling time. However, the usually adopted Kuramoto–Sivashinsky (KS) model involving the Bradley–Harper (BH) theory failed to explain the experimental results, nor the KS model that combines both the BH and Ehrlich–Schwoebel (ES) effects. We reexamined the ES term in the KS equation, and derived new terms reflecting the ES contribution. With such a modification, the KS model involving both the BH and the refined ES effects finally gave a qualitative explanation to the PIM result.
Keywords: Silicon; Surface structure; Morphology; Roughening and topography; Ion bombardment; Atomic force microscopy;
Improving pattern precision of chromium based black matrix by annealing by Shang-Chou Chang (2244-2249).
Black matrix is a major component of color filter used for blocking light in flat panel industry. Films made of chromium (Cr) and its two oxide/nitride combination layers are commonly used in black matrix for its high optical density and material stability. Each single Cr based layer film of the three multilayer combinations was produced on glass and then annealed in low pressure hydrogen environment. Etching, transmittance of visible light, and microstructure of these films without and with annealing were compared. It was found that annealing can mend the interference between the incident and reflected light for Cr based black matrix. Annealing can also improve the undercut defect and thus pattern precision. The lateral etching rates of Cr based films were found to be much lower and close to one another after annealing. It can be explained the film density and adhesion increase caused by the annealing process. This article provides a potential method in color filter fabrication to improve contrast and color interference issues if Cr based black matrix is used in display application.
Keywords: Cr based black matrix; Pattern precision; Annealing; Undercut;
Growth of transparent conducting nano-structured In doped ZnO thin films by pulsed DC magnetron sputtering by Young Ran Park; Eung Kwon Kim; Donggeun Jung; Tae Seok Park; Young Sung Kim (2250-2254).
Transparent conducting nano-structured In doped zinc oxide (IZO) thin films are deposited on corning 7059 glass substrates by bipolar pulsed DC magnetron sputtering with variation of pulsed frequency and substrate temperature. Highly c-axis oriented IZO thin films were grown in perpendicular to the substrate on the 30 kHz and 500 °C. The IZO films exhibited surface roughness of 3.6 nm similar to the commercial ITO and n-type semiconducting properties with electrical resistivity (carrier mobility) of about 5 × 10−3 Ω cm (14 cm2/V s). The optical characterization showed high transmittance of over 85% in the UV–vis region and exhibited the absorption edge of near 350 nm. In micro-Raman spectra, the origin of two additional modes is attributed to the host lattice defect due to the addition of In dopant. These results suggest that the IZO film can possibly be applied to make transparent conducting electrodes for flat panel displays.
Keywords: Nano-structured; Pulse DC magnetron sputtering; In doped ZnO (IZO); Transparent conducting oxide (TCO);
Detection of stress corrosion cracking of high-strength steel used in prestressed concrete structures by acoustic emission technique by S. Ramadan; L. Gaillet; C. Tessier; H. Idrissi (2255-2261).
The stress corrosion cracking (SCC) of high-strength steel used in prestressed concrete structures was studied by acoustic emission technique (AE). A simulated concrete pore (SCP) solution at high-alkaline (pH ≈ 12) contaminated by sulphate, chloride, and thiocyanate ions was used. The evolution of the acoustic activity recorded during the tests shows the presence of several stages related respectively to cracks initiation due to the local corrosion imposed by corrosives species, cracks propagation and steel failure. Microscopic examinations pointed out that the wires exhibited a brittle fracture mode. The cracking was found to propagate in the transgranular mode. The role of corrosives species and hydrogen in the rupture mechanism of high-strength steel was also investigated. This study shows promising results for an potential use in situ of AE for real-time health monitoring of eutectoid steel cables used in prestressed concrete structures.
Keywords: Acoustic emission; High-strength steel; Stress corrosion cracking; Local corrosion; Hydrogen assisted cracking;
Preparation and characterization of nickel nano-Al2O3 composite coatings by sediment co-deposition by Qiuyuan Feng; Tingju Li; Hongyun Yue; Kai Qi; Fudong Bai; Junze Jin (2262-2268).
Ni–Al2O3 composite coatings were prepared by using sediment co-deposition (SCD) technique and conventional electroplating (CEP) technique from Watt's type electrolyte without any additives. The microstructure, hardness, and wear resistance of resulting composites were investigated. The results show that the incorporation of nano-Al2O3 particles changes the surface morphology of nickel matrix. The preferential orientation is modified from (2 0 0) plane to (1 1 1) plane. The microhardness of Ni–Al2O3 composite coatings in the SCD technique are higher than that of the CEP technique and pure Ni coating and increase with the increasing of the nano-Al2O3 particles concentration in plating solution. The wear rate of the Ni–Al2O3 composite coating fabricated via SCD technique with 10 g/l nano-Al2O3 particles in plating bath is approximately one order of magnitude lower than that of pure Ni coating. Wear resistance for SCD obtained composite coatings is superior to that obtained by the CEP technique. The wear mechanism of pure Ni and nickel nano-Al2O3 composite coatings are adhesive wear and abrasive wear, respectively.
Keywords: Sediment co-deposition; Composite coatings; Nano-particles; Microhardness; Wear resistance;
The influence of process parameters on deposition characteristics of a soft/hard composite coating in kinetic spray process by Sumin Shin; Yuming Xiong; Youlgwun Ji; Hyung Jun Kim; Changhee Lee (2269-2275).
In kinetic spray processes, the non-uniformity of resultant composite coatings is generally caused by the difference in critical velocity and deposition efficiency between the components of a mixed feedstock. In the present paper, the effects of process parameters, such as feed rate, spray distance, and particle velocity, on the compositional variation between the mixed feedstock and resultant composite coating have been investigated. The results showed that the high diamond fraction in the coating can be achieved using a low feed rate, intermediate spray distance, and high impact particle velocity. The possibility of impact between hard brittle diamond particles is the main factor affecting the diamond fraction in the coating. Although the deposition efficiency, diamond fraction, and bond strength of the coating increase with particle velocity, a slight decrease of cohesive strength between diamond particle and bronze base was also observed.
Keywords: Kinetic spraying; Soft/hard composite; Process parameters; Deposition efficiency; Bond strength;
Characterization of the nitrided layers of XC38 carbon steel obtained by R.F. plasma nitriding by M. Keddam (2276-2280).
XC38 carbon steel was nitrided in a low-pressure R.F. plasma using a mixture of 60% N2-40% H2 without cathodic bias on the samples. The experiments were carried out at different temperatures for various time durations. The generated nitride layers were characterized by SEM observations, XRD and GDOS analyses. These analyses indicate that the compound layer was composed of the γ′-Fe4N phase with a surface content of N close to 6 wt%. An approach was used to study the growth kinetics of the compound layer at 500 °C. Furthermore, it was concluded that its kinetics follows a power law, which deviates from the classical parabolic growth.
Keywords: R.F. plasma; Iron nitride; Kinetics; Nitriding; Compound layer;
Au doped Sb3Te phase-change material for C-RAM device by Feng Wang; Ting Zhang; Chun-liang Liu; Zhi-tang Song; Liang-cai Wu; Bo Liu; Song-lin Feng; Bomy Chen (2281-2284).
Au doped Sb3Te phase-change films have been investigated by means of in situ temperature-dependent resistance measurement. Crystallization temperature of 2 at.% Au doped Sb3Te has been enhanced to 161 °C, which leads to a better data retention. The physical stability of the film has been improved evidently after adding Au as well. Resistance contrast has been improved to 1.1 × 104, one order of magnitude higher than that of pure Sb3Te. X-ray diffraction patterns indicate the polycrystalline Au–SbTe series have hexagonal structure, similar with pure Sb3Te alloy, when Au doping dose is less than 9 at.%.
Keywords: Phase-change; Crystallization temperature; Data retention; Au doped Sb3Te;
Studies of the collision frequency of ideal gas particles with the surfaces of the objects created using the ballistic deposition technique by T. Panczyk; T.P. Warzocha; W. Rudzinski (2285-2291).
This paper is a continuation of our studies of the collision frequency of ideal gas particles with the rough/fractal surfaces. Here, we applied a more realistic surface growth model, i.e. ballistic deposition for creation of fractal objects. We found that the collision frequency with irregular surfaces is the linear function of pressure and this frequency per unit pressure is quite a complicated function of the surface fractal dimension as well as the diameter of colliding particle. The collision frequency with rough surfaces cannot be exactly described by the analytical formula called the Langmuir–Hertz equation. However, we have stated that the deviations of the true collision frequency from the Langmuir–Hertz prediction are not huge and in typical catalytic studies the error introduced by replacing the true frequency by the Langmuir–Hertz prediction can be safely neglected. We have also studied the probability of finding on the surface an atom which has been hit a certain number of times by a gas particle. This probability reveals an interesting behaviour for small gas particles, i.e. it perfectly correlates with the number of directions from which the surface atom is accessible from the gas phase. We have also estimated the evolution of the adsorption energy distribution with the increasing fractal dimension of the surface in the ballistic deposition.
Keywords: Roughness; Fractal; Frequency of collisions; Adsorption energy; Geometric irregularity;
Characterization of the oxides formed at 1000 °C on the AISI 304 stainless steel by X-ray diffraction and infrared spectroscopy by N. Karimi; F. Riffard; F. Rabaste; S. Perrier; R. Cueff; C. Issartel; H. Buscail (2292-2299).
The aim of this work is to show the contribution of the infrared spectroscopy (FT-IR) to the identification of the oxides formed on the AISI 304 stainless steel during isothermal oxidation at 1000 °C, in air. This work focuses on the differentiation of spinel type AB2O4 structures and corundum type M2O3 structures. It is shown that after 100 h oxidation, the scale is composed of two subscales. The structural analyses were performed both on the adherent subscale and on the external subscale, which spalled off during cooling to room temperature. In the spalled subscale, the infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analyses exhibit the presence of two spinel phases: Mn1.5Cr1.5O4 and FeCr2O4, as well as hematite Fe2O3. The FT-IR and XRD analyses of the adherent subscale enable us to distinguish the spinel Mn1.5Cr1.5O4 and FeCr2O4 structures which are difficult to identify by XRD alone. Chromia Cr2O3 appears to be slightly present in the adherent subscale. According to our results, the parabolic regime of the kinetic curve corresponds to a scale growth mechanism governed by an inward oxygen diffusion.
Keywords: AISI 304 stainless steel; XRD; FT-IR; High temperature oxidation;
Grafting of copolymer styrene maleic anhydride on poly(ethylene terephthalate) film by chemical reaction and by plasma method by Muriel Bigan; Julien Bigot; Brigitte Mutel; Xavier Coqueret (2300-2308).
This work deals with the chemical grafting of a styrene maleic anhydride copolymer on the surface of a previously hydrolyzed polyethylene terephthalate (PET) film 12 μm thick via covalent bond. Two different ways are studied. The first one involves an activation of the hydrolyzed PET by the triethylamine before the grafting step. In the second one, the copolymer reacts with the 4-dimethylaminopyridine in order to form maleinyl pyridinium salt which reacts with alcohol function of the hydrolyzed PET. Characterization and quantification of the grafting are performed by Fourier transform infrared spectroscopy. Factorial experiment designs are used to optimize the process and to estimate experimental parameters effects. The opportunity to associate the chemical process to a cold remote nitrogen plasma one is also examined.
Keywords: PET; Plasma applications; Plasma-materials interactions; Design of experiments; Infrared spectroscopy chemical analysis; Chemical reactions of polymers;
The Fe/ZnO(0 0 0 1) interface: Formation and thermal stability by D. Wett; A. Demund; H. Schmidt; R. Szargan (2309-2318).
The room temperature growth mode and the interface reaction of Fe films on single crystalline ZnO(0 0 0 1) substrates prepared in ultra high vacuum (UHV) has been investigated by means of X-ray photoelectron and Auger electron spectroscopy (XPS, AES), low energy electron diffraction (LEED) and low energy ion scattering spectroscopy (LEIS). The results show that Fe grows in the pseudo layer-by-layer mode. At ambient temperature the deposited Fe film reduces the underlying ZnO single crystal resulting in FeO at the interface and metallic Zn, which partially diffuses into the remaining Fe overlayer. Annealing leads to a stepwise oxidation of the Fe to FeO (670 K) and Fe2O3 (820 K). The Fe2O3 mixes with the substrate resulting in two (1 1 1) oriented textures of a spinel phase found by electron backscatter diffraction analysis (EBSD). Fe-based spin-injection may play a vital role for ZnO-based spintronic devices.
Keywords: Zinc oxide; ZnO; Iron; Fe; Iron oxide; FeO; Fe2O3; Interface; Epitaxy; Growth; X-ray photoelectron spectroscopy; XPS; Low energy ion scattering; LEIS; Low energy electron diffraction; LEED; Electron backscatter diffraction; EBSD;
Surface study of fine MgFe2O4 ferrite powder prepared by chemical methods by Hiromichi Aono; Hideyuki Hirazawa; Takashi Naohara; Tsunehiro Maehara (2319-2324).
To study surface behaviors, MgFe2O4 ferrite materials having different grain sizes were synthesized by two different chemical methods, i.e., a polymerization method and a reverse coprecipitation method. The single phase of the cubic MgFe2O4 was confirmed by the X-ray diffraction method for both the precursors decomposed at 600–1000 °C except for a very small peak of Fe2O3 was detected for the samples calcined at 600 and 700 °C by the polymerization method. The crystal size and particle size increased with an increase in the sintering temperature using both methods. The conductance of the MgFe2O4 decreased when the atmosphere was changed from ambient air to air containing 10.0 ppm NO2. The conductance change, C = G(air)/G(10 ppm NO2), was reduced with an increase in the operating temperature. For the polymerization method, the maximum C-value was ca. 40 at 300 °C for the samples sintered at 900 °C. However, the samples sintered at 1000 °C showed a low conductance change in the 10 ppm NO2 gas, because the ratio of the O2 gas adsorption sites on the particle surface is smaller than those of the samples having a high C-value. The low Mg content on the surface affects the low ratio of the gas adsorption sites. For the reverse coprecipitation method, the particle size was smaller than that of the polymerization method. Although a stable conductance was obtained for the sample sintered at 900 and 1000 °C, its conductance change was less than that of the polymerization method.
Keywords: MgFe2O4 ferrite; NO2 gas adsorbtion; Semiconductor; XRD; XPS;
The role of halide ions on the electrochemical behaviour of iron in alkali solutions by S. Nathira Begum; V.S. Muralidharan; C. Ahmed Basha (2325-2330).
Active dissolution and passivation of transition metals in alkali solutions is of technological importance in batteries. The performance of alkaline batteries is decided by the presence of halides as they influence passivation. Cyclic voltammetric studies were carried out on iron in different sodium hydroxide solutions in presence of halides. In alkali solutions iron formed hydroxo complexes and their polymers in the interfacial diffusion layer. With progress of time they formed a cation selective layer. The diffusion layer turned into bipolar ion selective layer consisted of halides, a selective inner sublayer to the metal side and cation selective outer layer to the solution side. At very high anodic potentials, dehydration and deprotonation led to the conversion of salt layer into an oxide.
Keywords: Cyclic voltammetry; Iron dissolution; Passivation; Halide ions;
Liquid phase epitaxial growth and optical property of flower-like ZnO nanosheets on Zinc foil by Chong Jia; Xinhua Zhang; Yiqing Chen; Yong Su; Qingtao Zhou; Minjun Xin; Yousheng Lv; Weihai Kong (2331-2335).
Large scale flower-like ZnO nanosheets have been synthesized on Zinc foil by a simple hydrothermal method. Their morphology and microstructures were characterized and analyzed by X-ray spectroscopy (XRD), field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HRTEM). The as-synthesized flower-like nanosheets are hexagonal phase single crystal with 200–300 nm in width, 50 nm in thickness. The growth process follows the liquid phase epitaxial growth mechanism. In this approach, the ZnO buffer is used as substrate for the growth of flower-like ZnO nanosheets. The growth direction of the nanosheets is the preferential [0 0 0 1] growth direction of ZnO. The photoluminescence spectrum of the sample exhibits only a sharp and strong UV emission centered at 386 nm, which indicates that the flower-like ZnO nanosheets on Zn foil are of good optical property.
Keywords: Substrates; Hydrothermal crystal growth; Liquid phase epitaxy; Nanomaterials; ZnO;
Composition-spread thin films of pentacene and 6,13-pentacenequinone fabricated by using continuous-wave laser molecular beam epitaxy by Seiichiro Yaginuma; Kenji Itaka; Yuji Matsumoto; Tsuyoshi Ohnishi; Mikk Lippmaa; Takahiro Nagata; Toyohiro Chikyow; Hideomi Koinuma (2336-2341).
Synthesis of continuous composition-spread (CCS) thin films is widely recognized in combinatorial material science as a powerful technique for rapidly investigating the properties of new functional materials. However, there are very few reports of CCS organic thin films due to the fact that the thermal evaporation method with Knudsen cells, which is commonly used to fabricate organic thin films in vacuum, does not offer the necessary level of deposition rate control as, for example, does pulsed laser deposition (PLD). We have successfully fabricated organic CCS thin films of pentacene and 6,13-pentacenequinone by continuous-wave laser molecular beam epitaxy (CWL-MBE), which we developed as a new fabrication method for organic thin films. The composition-spread films were characterized systematically by ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, atomic force microscopy, and two-probe conductivity measurements. The present work brings the advantages of high-throughput parallel synthesis and systematic characterization to the field of organic electronics, allowing for quick exploration and rapid optimization of organic functional materials and devices.
Keywords: Continuous-wave laser MBE; Composition spread; Pentacene; 6,13-Pentacenequinone;
Microstructural and electrochromic properties of tungsten oxide thin films produced by surfactant mediated electrodeposition by M. Deepa; A.K. Srivastava; S.N. Sharma; Govind; S.M. Shivaprasad (2342-2352).
By electrochemically controlling the structure of the surface aggregates, the grain microstructure has been optimized to yield mesoporous thin films of tungsten oxide (WO3) at the electrode–electrolyte interface in a peroxotungstate sol in the presence of a structure-directing agent (Triton) at room temperature. Apart from the dominant ultrafine nanocrystallites and pores (5–10 nm), well-developed abutting grains (25–100 nm) and nanofibrils also constitute an integral part of the film matrix. X-ray photoemission spectra reveal the as-deposited film (WO3−x ) to be constituted by a high proportion of W6+ states with a low oxygen deficiency (x = 0.02). A relatively high W5+ content in the film, upon intercalation of 18 mC cm−2 charge translates into a large coloring efficiency (η VIS ∼ 70 cm2 C−1) and transmission modulation. At a lithium intercalation level of 22 mC cm−2, in addition to W5+ and W6+ states, the film also comprises of W4+ states. The extremely fast color-bleach kinetics (3 and 2 s, respectively, for a 50% change in transmittance) shown by the as-deposited WO3 film are repercussions of the mesopore morphology, the multiple nanostructures and the sixfold channels of its hexagonal modification. The film shows a high cycling stability as the switching times do not show any significant decline even after 3500 repetitive cycles. Coloration efficiency over the solar and photopic regions and current density for lithium intercalation for the as-deposited film are superior to that observed for the films annealed at 100, 250 and 500 °C. The abysmal electrochromic response of the annealed films is a consequence of surface defects like cracks and uncontrolled densification and pore shrinkage.
Keywords: Tungsten oxide; Nanostructured; Mesoporous; Electrochromic; Triton;
Synthesis and characterization of (h 0 h)-oriented silicalite-1 films on α-Al2O3 substrates by Lin Lang; Xiufeng Liu; Baoquan Zhang (2353-2358).
A simple and well-designed synthesis procedure is proposed to fabricate silicalite-1 films on porous α-Al2O3 substrates on purpose of preventing the aluminum leaching. The continuous and 2 μm thick seed layer of silicalite-1 crystals is fabricated by using a spin coater. The first-time seeded growth is performed to synthesize a thin layer of intergrown ZSM-5 crystals on the silicalite-1 seed layer, where the use of low alkalinity and short synthesis time is to reduce the aluminum leaching. The intergrown layer of ZSM-5 crystals serves as a barrier to block the aluminum leaching from porous α-Al2O3 substrates in the second-time seeded growth, leading to the formation of ca. 11 μm thick intergrown and oriented silicalite-1 films with an extremely high Si/Al ratio. According to SEM images and XRD measurements, the as-synthesized silicalite-1 film is dense, continuous, and (1 0 1)-oriented. The electron probe microanalysis (EPMA) of the resulting film demonstrates that there is no aluminum leaching in the second-time seeded growth. The leaking tests confirm that non-zeolitic pores in the silicalite-1 film are negligible.
Keywords: Silicalite-1; Thin film; Orientation;
Dry etching of CuCrO2 thin films by W.T. Lim; P.W. Sadik; D.P. Norton; S.J. Pearton; F. Ren (2359-2363).
Highly conducting films of p-type CuCrO2 are attractive as hole-injectors in oxide-based light emitters. In this paper, we report on the development of dry etch patterning of CuCrO2 thin films. The only plasma chemistry that provided some chemical enhancement was Cl2/Ar under inductively coupled plasma conditions. Etch rates of ∼500 Å min−1 were obtained at chuck voltages around −300 V and moderate source powers. In all cases, the etched surface morphologies were improved relative to un-etched control samples due to the smoothing effect of the physical component of the etching. The threshold ion energy for the onset of etching was determined to be 34 eV. Very low concentrations (≤1 at.%) of residual chlorine were detected on the etched surfaces but could be removed by simple water rinsing.
Keywords: CuCrO2; Etching; Surface morphology;
Control of tribological properties of diamond-like carbon films with femtosecond-laser-induced nanostructuring by Naoki Yasumaru; Kenzo Miyazaki; Junsuke Kiuchi (2364-2368).
This paper reports tribological properties of diamond-like carbon (DLC) films nanostructured by femtosecond (fs) laser ablation. The nanostructure was formed in an area of more than 15 mm × 15 mm on the DLC surface, using a precise target-scan system developed for the fs-laser processing. The frictional properties of the DLC film are greatly improved by coating a MoS2 layer on the nanostructured surface, while the friction coefficient can be increased by surface texturing of the nanostructured zone in a net-like patterning. The results demonstrate that the tribological properties of a DLC surface can be controlled using fs-laser-induced nanostructuring.
Keywords: Femtosecond-laser ablation; Nanostructure; Tribology; Diamond-like carbon;
Structural, optical and morphological studies on laser ablated nanostructured WO3 thin films by K.J. Lethy; D. Beena; R. Vinod Kumar; V.P. Mahadevan Pillai; V. Ganesan; Vasant Sathe (2369-2376).
Thin films of tungsten trioxide (WO3) are prepared by reactive pulsed laser deposition (PLD) technique on glass substrates at three different substrate temperatures (T s). The structural, morphological and optical properties of the deposited films are systematically studied using X-ray diffraction (XRD), grazing incidence X-ray diffraction (GIXRD), micro-Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-VIS spectrophotometry techniques. X-ray diffraction analysis reveals that crystalline WO3 films can grow effectively even at 300 K at an oxygen pressure of 0.12 mbar. All the films deposited at various T s exhibit mixed oxide phase consisting of orthorhombic and triclinic phase of tungsten oxide with a preferred orientation along (0 0 1) lattice plane reflection. Micro-Raman results are consistent with X-ray diffraction findings. The SEM analysis shows that deposited films are porous and crystalline grains are of nano-metric dimension. The effect of T s on mean surface roughness studied by AFM analysis reveals that mean surface roughness decreases with increase in T s. The optical response of WO3 layers measured using UV-VIS spectrophotometry is used to extract the optical constants such as refractive index (n), extinction coefficient (k) and optical band gap (E g), following the method of Swanepoel.
Keywords: Tungsten trioxide nanostructured thin films; Pulsed laser deposition; Micro-Raman spectra; Scanning electron microscopy; Porous materials; Atomic force microscopy; Refractive index calculation; Extinction coefficient; Effect of substrate temperature;
Hydrogen dissociation on oxide covered MgH2 by catalytically active vacancies by A. Borgschulte; M. Bielmann; A. Züttel; G. Barkhordarian; M. Dornheim; R. Bormann (2377-2384).
MgH2 is an important ingredient in modern reactive hydride composites to be used as hydrogen storage materials. The surface composition and chemical state of ball-milled MgH2 is studied during hydrogen desorption by means of X-ray photoelectron spectroscopy. Simultaneously, the desorption rate of hydrogen is monitored, which is compared to dissociative properties of the surface investigated by hydrogen–deuterium exchange experiments. It is found that MgH2 is also oxide covered during desorption demonstrating that MgO is able to recombine atomic hydrogen. The corresponding catalytic sites are associated with low coordinated surface vacancies on the oxide. The maximum surface concentration of these vacancies is very small, which is countered by a very high turnover frequency due to a small activation energy for dissociation of hydrogen of 0.1 eV on the single vacancy. The study provides insight into the catalytic role played by the oxide additives in MgH2, which are superior catalysts for hydrogen sorption even when compared to 3d-metals.
Keywords: Hydrogen storage; Catalytic sites; H/D exchange; Photoelectron spectroscopy; XPS; Surface vacancies;
Role of oil derived carbonaceous phase in the performance of sewage sludge-based materials as media for desulfurizaton of digester gas by Karifala Kante; Jieshan Qiu; Zongbin Zhao; Yu Chang; Teresa J. Bandosz (2385-2395).
Desulfurization adsorbents for purification of digester gas were prepared by pyrolysis of sewage sludge impregnated with spent mineral oil. To evaluate the changes in the structural and chemical properties the pyrolysis time and temperature varied. The materials were characterized using adsorption of nitrogen, FTIR, XRD, ICP, SEM and thermal analysis. Their catalytic activity was tested in the removal of hydrogen sulfide from simulated mixture of digester gas. The results indicated the importance of new carbon phase from the oil precursor. It provided mesoporosity, which increased the dispersion of catalytic phase and space for storage of surface reaction products. The results indicated that the adsorbents obtained at 950 °C are much more active in the process of hydrogen sulfide oxidation than those obtained at 650 °C. Moreover, longer heat treatment is also beneficial for the development of surface catalytic properties. Extensive pyrolysis stabilizes carbon phase via increasing its degree of aromatization and provides activation agents for this phase coming from decomposition and rearrangement of inorganic phase.
Keywords: Sewage sludge; Waste oil; Pyrolysis; Porosity; Surface chemistry; Catalytic activity;
Surface and bulk thermal annealing effects on ZnO crystals by Wantae Lim; V. Craciun; K. Siebein; B.P. Gila; D.P. Norton; S.J. Pearton; F. Ren (2396-2400).
Annealing at temperatures up to 1000 °C is shown to decrease band edge photoluminescence in bulk ZnO crystals and increase deep level-related emission. The surface roughens for anneals in the range of 600–800 °C as O is lost preferentially from the surface, but at 900 °C the morphology improves as excess Zn is also lost from the surface. Splitting of the peak in the rocking curve of the ZnO (0 0 2) plane after annealing at 900–1000 °C indicates that the substrate is a mosaic of two or more crystals oriented slightly differently from one another and we are detecting differences in orientation of some of the grains in different areas or small changes due to annealing. There was no significant change in bulk conductivity of the ZnO for anneals up to 1000 °C, suggesting that ion implantation followed by annealing may be an effective approach for doping in this.
Keywords: ZnO; Annealing;
Influence of substrate temperature on electrical and optical properties of p-type semitransparent conductive nickel oxide thin films deposited by radio frequency sputtering by Lei Ai; Guojia Fang; Longyan Yuan; Nishuang Liu; Mingjun Wang; Chun Li; Qilin Zhang; Jun Li; Xingzhong Zhao (2401-2405).
Nickel oxide thin films were deposited on fused silica and Si(1 0 0) substrates at different substrate temperatures ranging from room temperature to 400 °C using radio frequency reactive magnetron sputtering from a Ni metal target in a mixture of O2 and Ar. With the increase of substrate temperature, nickel oxide films deposited on the Si substrates exhibit transition from amorphous to poly-crystalline structures with different preferred orientations of NiO(2 0 0) and (1 1 1). The films deposited at higher temperature exhibit higher Ni2+/Ni3+ ratio. With substrate temperature increasing from room temperature to 400 °C, the electrical resistivities of nickel oxide films increase from (2.8 ± 0.1) × 10−2 to (8.7 ± 0.1) Ω cm, and the optical band-gap energies increase from 3.65 to 3.88 eV. A p-nickel oxide/n-zinc oxide heterojunction was fabricated to confirm the p-type conduction of nickel oxide thin film, which exhibited a steadily rectifying behavior.
Keywords: Nickel oxide; p-Type; RF sputtering; Heterojunction;
Preparation of photocatalytic Fe2O3–TiO2 coatings in one step by metal organic chemical vapor deposition by Xingwang Zhang; Lecheng Lei (2406-2412).
There are two major difficulties in the TiO2 liquid–solid photocatalytic system: effective immobilization of the TiO2 particles; and improving the catalytic activity under visible light. To simultaneously solve these two problems, Fe2O3–TiO2 coatings supported on activated carbon fiber (ACF), have been prepared in one step by a convenient and efficient method—metal organic chemical vapor deposition (MOCVD). XRD results revealed that Fe2O3–TiO2 coatings mainly composed of anatase TiO2, α-Fe2O3 phases and little Fe2Ti3O9. The pore structure of ACF was preserved well after loading with Fe2O3–TiO2 coatings. UV–vis diffuse reflectance spectra showed a slight shift to longer wavelengths and an enhancement of the absorption in the visible region for Fe2O3–TiO2 coatings, compared to the pure TiO2 sample. A moderate Fe2O3–TiO2 loading (13.7 wt%) was beneficial to mineralizing wastewater because the intermediates could be adsorbed onto the surface of photocatalyst following decomposition. The stable performance revealed that the Fe2O3–TiO2 coatings were strongly adhered to the ACF surface, and the as prepared catalysts could be reused showing potential application for wastewater treatment.
Keywords: MOCVD; TiO2; Fe2O3; Visible light; Photocatalysis;
Preparation and reactivity of aluminum nanopowders coated by hydroxyl-terminated polybutadiene (HTPB) by Liangui Guo; Wulin Song; Mulin Hu; Changsheng Xie; Xia Chen (2413-2417).
HTPB-coated aluminum (Al) nanopowders were prepared by laser-induction complex heating. The characterization of the nanopowders was revealed using transmission electronic microscopy (TEM), high-resolution transmission electronic microscopy (HRTEM), X-ray diffraction analysis (XRD) and Fourier transform infrared (FTIR) spectrometry. Results showed that HTPB-coated Al nanopowders have a core-shell structure with size ranging from 30 to 100 nm and organic HTPB exists in HTPB-coated Al nanopowders. Differential scanning calorimeter (DSC) and thermal gravimeter (TG) analysis of the HTPB-coated Al nanopowders and Al2O3-passivated Al nanopowders stored for 2 years in ambient environment indicated that the reactivity and stability of HTPB-coated Al nanopowders outperform Al2O3-passivated Al nanopowders. These findings demonstrate that HTPB is a suitable surface coating material for Al nanopowders.
Keywords: Aluminum; Nanopowder; Surface coating; Reactivity; Oxidation; DSC-TG;
Electrodeposition and properties of Zn-nanosized TiO2 composite coatings by B.M. Praveen; T.V. Venkatesha (2418-2424).
Nanosized TiO2 particles were prepared by sol–gel method. The TiO2 particles were co-deposited with zinc from a sulphate bath at pH 4.5 using electrodeposition technique. The corrosion behavior of the coatings was assessed by electrochemical polarization, impedance, weight-loss and salt spray tests. Wear resistance and microhardness of the composite coating was measured. The smaller grain size of the composite coatings was observed in the presence of TiO2 and it was confirmed by the images of scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques.
Keywords: TiO2; Nano-particles; Corrosion; Wear; Microhardness;
Structure and tribological properties of amorphous carbon films deposited by electrochemical method on GCr15 steel substrate by Qun-feng Zeng; Guang-neng Dong; You-bai Xie (2425-2430).
Amorphous carbon films were deposited on GCr15 steel substrates by electrolysis of methanol, dimethylsulfoxide (DMSO) and the methanol–DMSO intermixture electrolytes, respectively, under high voltage and low temperature conditions. The microstructure and wear morphology of the deposited films were analyzed using X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM) combined with energy dispersive X-ray fluorescence spectrometer (EDX), respectively. The tribological properties of the films were evaluated using a ball-on-disk rotating friction tester under dry friction condition. The results show that the films deposited by electrodeposition technique on GCr15 steel substrates are amorphous carbon films. It is also found that the electrolytes have an obvious influence on the tribological properties of the deposited films with the electrodeposition method. The tribological properties of the films deposited with the intermixture electrolyte are better than those of the films deposited by other pure electrolytes. The related growth mechanism of the films in the liquid-phase electrodeposition is discussed as well in this study. Via the reaction of the ―CH3 groups with each other to form carbon network and reaction of the ―CH3 and SO2+ groups to achieve the doping of sulfur atom in the carbon network, respectively, in other words, amorphous carbon films can be obtained on GCr15 steel substrates by electrodeposition technique.
Keywords: Amorphous carbon films; Electrodeposition technique; Tribological properties;
Microwave-induced electrophilic addition of single-walled carbon nanotubes with alkylhalides by Yang Xu; Xianbao Wang; Rong Tian; Shaoqing Li; Li Wan; Mingjian Li; Haijun You; Qin Li; Shimin Wang (2431-2435).
We report the microwave-induced electrophilic addition of single-walled carbon nanotubes (SWNTs) with alkylhalides using Lewis acid as a catalyst followed by hydrolysis. The reaction results in the attachment of alkyl and hydroxyl groups to the surface of the nanotubes. This rapid and high-energy microwave radiation is found to be highly efficient for this reaction, which only needs as low as several minutes. The resulting nanotubes were characterized with FTIR, UV–vis–NIR, Raman, TGA, TEM and AFM. It demonstrates that iodo-alkanes show higher reaction activity with SWNTs than chloro- and bromo-alkanes.
Keywords: Carbon nanotubes; Microwave irradiation; Electrophilic addition reaction; Alkylhalides;
The effect of NO/O2 ratio in NO–CO–O2 reaction on a catalytic surface: A computer simulation study by Waqar Ahmad; E.V. Albano (2436-2440).
The interaction among the reacting species in the NO–CO–O2 reaction on a metal catalytic surface that proceeds according to the Langmuir–Hinshelwood mechanism is studied by means of Monte Carlo simulation. The study of this three-component system is essential for the understanding of the influence of NO/O2 ratio on the catalytic reduction of NO into N & O and oxidation of CO to CO2. It is found that this complex system, which has not been studied on these lines before, exhibits irreversible phase transitions between active states with sustained reaction and poisoned states with the catalytic surface fully covered by the reactants. The phase diagrams of the surface coverage with CO, N or O and the steady state production of CO2 are evaluated as a function of the partial pressure of CO in the gas phase. From this study, it is observed that with the addition of NO in the CO–O2 reaction, the critical points in the phase diagram move towards lower values of CO partial pressure but the width of reaction window remains almost the same. However, the maximum production rate of CO2 decreases continuously. On the other hand, the addition of O2 in the NO–CO reaction shifts the critical points towards higher values of CO pressure. Moreover, the width of reaction window as well as the production rate of CO2 increases with the increase in O2 concentration.
Keywords: Catalytic surfaces; Adsorption; Phase transitions; Surface coverage; Monte Carlo simulation;
Analysis of XPS spectra of Fe2+ and Fe3+ ions in oxide materials by Toru Yamashita; Peter Hayes (2441-2449).
Samples of the iron oxides Fe0.94O, Fe3O4, Fe2O3, and Fe2SiO4 were prepared by high temperature equilibration in controlled gas atmospheres. The samples were fractured in vacuum and high resolution XPS spectra of the fractured surfaces were measured. The peak positions and peak shape parameters of Fe 3p for Fe2+ and Fe3+ were derived from the Fe 3p XPS spectra of the standard samples of 2FeO·SiO2 and Fe2O3, respectively. Using these parameters, the Fe 3p peaks of Fe3O4 and Fe1−y O are analysed. The results indicate that high resolution XPS techniques can be used to determine the Fe2+/Fe3+ ratios in metal oxides. The technique has the potential for application to other transition metal oxide systems.
Keywords: XPS; Iron oxide; Quantitative analysis; Chemical state;
Characterization and ethylene adsorption of natural and modified clinoptilolites by Burcu Erdoğan; Meryem Sakızcı; Ertuğrul Yörükoğulları (2450-2457).
The ethylene adsorption of Turkey clinoptilolite-rich tuff from Gordes and Bigadic region of western of Anatolia and their exchanged forms (K+, Na+ and Ca2+) were investigated. The clinoptilolite samples were characterized using XRD, TG–DTA and nitrogen adsorption methods. Adsorption isotherms for ethylene on natural and modified forms of both adsorbents at 277 K and 293 K were obtained at pressures up to 38 kPa. Uptake of ethylene increased as Na-CLN < Ca-CLN < K-CLN < Natural CLN for Gordes zeolite at 277 K, 293 K and for Bigadic zeolite at 277 K. For Bigadic zeolites at 293 K, uptake of ethylene increased in the order Ca-CLN < Na-CLN < K-CLN < Natural CLN. It was found that ethylene adsorption capacity of Bigadic clinoptilolite samples was much greater than Gordes clinoptilolite samples except K+ modified forms at both temperatures. These results show that both natural clinoptilolites have a considerable potential for the removal of ethylene.
Keywords: Zeolites; Adsorption; Ethylene; Thermal properties; XRD;
Structural and optical properties of thermal evaporated magnesium phthalocyanine (MgPc) thin films by M.M. El-Nahass; A.A. Atta; H.E.A. El-Sayed; E.F.M. El-Zaidia (2458-2465).
X-ray powder diffraction (XRD) of MgPc indicated that the material in the powder form is polycrystalline with monoclinic structure. Miller indices, h k l, values for each diffraction peak in XRD spectrum were calculated. Thermal evaporation technique was used to deposit MgPc thin films. The XRD studies were carried out for MgPc thin films where the results confirm the amorphous nature for the as-deposited films. While, polycrystalline films orientated preferentially to (1 0 0) plane with an amorphous background were obtained for films annealed at 623 K for 3 h. Optical properties of MgPc thin films were characterised by using spectrophotometric measurements of transmittance and reflectance in the spectral range from 190 to 2500 nm. The refractive index, n, and the absorption index, k, were calculated. According to the analysis of dispersion curves, the parameters, namely; the optical absorption coefficient (α), molar extinction coefficient (ɛ molar), oscillator energy (E os), oscillator strength (f), and electric dipole strength (q 2) were also evaluated. The recorded absorption measurements in the UV–vis region show two well defined absorption bands of phthalocyanine molecule; namely the Q-band and the Soret (B-band). The Q-band showed its splitting characteristic (Davydov splitting), and ΔQ was obtained as 0.15 eV. The analysis of the spectral behaviour of the absorption coefficient (α), in the absorption region revealed indirect transitions. The transport and the near onset energy gaps were estimated as respectively 2.74 ± 0.02 and 1.34 ± 0.01 eV.
Keywords: Optical properties; MgPc thin films;
The behavior of lead during the solidification of Zn–0.1Al–0.1Pb coating on batch hot-dipped steel by Xinhua Wang; Jintang Lu; Chunshan Che; Gang Kong (2466-2471).
The typical spangle on batch hot-dipped Zn–0.1Al–0.1Pb alloy coating was investigated. The morphology, distribution, chemical composition and identification of the phases on coating surface were examined by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. It is found that most of spangles usually exhibit three distinct regions: smooth, feathery and coarse regions, of which lead surface segregation across the coating surface was detected increasingly more significant. Furthermore, lead micro-segregation with the form of tiny orthohexagonal particulates (<0.5 μm), mainly happens in the interdendritic spacing instead of the grain boundary probably owing to no sufficient diffusion. Based on the experimental results and compared to CGL, the solidification sequence of the Zn–0.1Al–0.1Pb coating was analyzed assisted with Zn–Pb phase diagram; the morphology of the spangle is modeled on consideration with the interaction of the thermal condition and the crystallization orientation; the profile of precipitated lead particulates is well explained in the view of crystallography.
Keywords: Hot dip galvanizing; Surface segregation; Equilibrium crystal shape; Spangle;
Investigation on the effect of RF air plasma and neem leaf extract treatment on the surface modification and antimicrobial activity of cotton fabric by K. Vaideki; S. Jayakumar; R. Rajendran; G. Thilagavathi (2472-2478).
A thorough investigation on the antimicrobial activity of RF air plasma and azadirachtin (neem leaf extract) treated cotton fabric has been dealt with in this paper. The cotton fabric was given a RF air plasma treatment to improve its hydrophilicity. The process parameters such as electrode gap, time of exposure and RF power have been varied to study their effect in improving the hydrophilicity of the cotton fabric and they were optimized based on the static immersion test results. The neem leaf extract (azadirachtin) was applied on fabric samples to impart antimicrobial activity. The antimicrobial efficacy of the samples have been analysed and compared with the efficacy of the cotton fabric treated with the antimicrobial finish alone. The investigation reveals that the RF air plasma has modified the surface of the fabric, which in turn increased the antimicrobial activity of the fabric when treated with azadirachtin. The surface modification due to RF air plasma treatment has been analysed by comparing the FTIR spectra of the untreated and plasma treated samples. The molecular interaction between the fabric, azadirachtin and citric acid which was used as a cross linking agent to increase the durability of the antimicrobial finish has also been analysed using FTIR spectra.
Keywords: Hydrophilicity; Antimicrobial activity; RF air plasma; Neem leaf extract (azadirachtin); FTIR spectrum;
Controlling surface states and photoluminescence of porous silicon by low-energy-ion irradiation by X.W. Du; Y. Jin; N.Q. Zhao; Y.S. Fu; S.A. Kulinich (2479-2482).
Porous silicon (PS) was irradiated by three kinds of low-energy ions with different chemical activity, namely argon ions, nitrogen ions and oxygen ions. The chemical activity of ions has significant effect on the surface states and photoluminescence (PL) properties of PS, The photoluminescence quenching after argon ions and nitrogen ions irradiation is ascribed to the broken Si–Si bonds, while the PL recovery is attributed to the oxidation of Si–H back bonds. Oxygen ions irradiation leads to the formation of a SiO x layer with oxygen defects and PS shows different PL evolution than PS irradiated by argon ions and nitrogen ions.
Keywords: Porous silicon; Optical properties; Fourier transform infrared spectroscopy (FTIR);
Synthesis and characterization of hard magnetic composites—Hollow microsphere/titania/barium ferrite by Guohong Mu; Xifeng Pan; Na Chen; Chihuan He; Mingyuan Gu (2483-2486).
Hard magnetic composites—hollow microsphere (core)/titania (intermediate layer)/barium ferrite (magnetic shell) (M/T/B) were prepared by wet-chemical method. Barium ferrite nanoparticles were directly coated on the rutile titania-coated hollow microsphere forming light hard magnetic composites using sol–gel technique. The prepared composites were characterized with FESEM, EDS, XRD and vibrating sample magnetometry. The composites are composed of barium ferrite, hematite, titania and mullite. For the samples with 40 wt.% barium ferrite, its specific saturation magnetization with titania is increased to 17.88 emu/g in comparison with 9.6 emu/g without titania. The function of titania in the composites is also discussed.
Keywords: Barium ferrite; Hollow microsphere; Titania; Magnetic properties; Sol–gel;
Imaging of ferroelectric vinylidene fluoride and trifluoroethylene copolymer films by scanning tunneling microscopy by GuoDong Zhu; ZhiGang Zeng; Li Zhang; XueJian Yan (2487-2492).
In this paper, we reported the possibility to image non-conducting P(VDF-TrFE) copolymer films by STM. The films had the thickness of ∼25.0 nm and were spin-coated onto Au or graphite substrates. For films deposited on Au substrates, STM images showed grain structures of ∼100 nm, much larger than the grains of bare Au substrate. With increased scan rate, the film surface was damaged by STM tip and extreme protrusions and holes were observed. For films deposited on graphite substrates, we only obtained an image of very flat plane and could not observe the topography of the film surface. It seemed that the tip had pierced through the uppermost P(VDF-TrFE) layers and only imaged the layers nearest to the substrate. Asymmetrical current–voltage curves were observed from copolymer films deposited on HOPG. Experimental results were discussed.
Keywords: Scanning tunneling microscopy (STM); Atomic force microscopy (AFM); P(VDF-TrFE); Surface morphology; Current–voltage characteristic;
Superhydrophobic properties of silver-coated films on copper surface by galvanic exchange reaction by A. Safaee; D.K. Sarkar; M. Farzaneh (2493-2498).
Hydrophobic properties of thin nanostructured silver films produced by galvanic exchange reaction on a copper surface were studied after passivation with stearic acid. The morphology of the silver films was controlled by varying the concentration of silver nitrate in the solution. Water contact angle as high as 156° and contact angle hysteresis as low as 5° were achieved for samples obtained with initial silver ion concentration of 24.75 mM in the solution. However, a strong dependence of contact angle and contact angle hysteresis on the fractal-like morphology of the silver films was observed with the variation of silver ion concentration.
Keywords: Superhydrophobicity; Microstructure; Electron microscopy; Galvanic exchange reaction;
Influence of atmospheric pressure plasma treatment time on penetration depth of surface modification into fabric by C.X. Wang; Y. Liu; H.L. Xu; Y. Ren; Y.P. Qiu (2499-2505).
In order to determine the relationship between the treatment duration of atmospheric pressure plasma jet (APPJ) and the penetration depth of the surface modification into textile structures, a four-layer stack of polyester woven fabrics was exposed to helium/oxygen APPJ for different treatment durations. The water-absorption time for the top and the bottom sides of each fabric layer was reduced from 200 s to almost 0 s. The capillary flow height for all fabric layers in the stack increased linearly with the treatment duration but the rate of increasing reduced linearly with the fabric layer number. A model for the capillary flow height as a function of treatment duration and the layer number was established based on the experimental data and the maximum penetration depth of the APPJ was predicted for the polyester fabric. The improved wettability of the fabrics was attributed to the enhanced surface roughness due to plasma etching and the surface chemical composition change due to plasma-induced chemical reaction as detected by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. The surface roughness and the surface chemical composition change diminished as the fabric layer number increased.
Keywords: Atmospheric pressure plasma; Penetration depth; Polyester fabric; Water-absorption time; Capillary flow height;
Carbon sputtering yield measurements at grazing incidence by Robert D. Kolasinski; James E. Polk; Dan Goebel; Lee K. Johnson (2506-2515).
In this investigation, carbon sputtering yields were measured experimentally at varying angles of incidence under Xe+ bombardment. The measurements were obtained by etching a coated quartz crystal microbalance (QCM) with a low energy ion beam. The material properties of the carbon targets were characterized with a scanning electron microscope (SEM) and Raman spectroscopy. C sputtering yields measured under Ar+ and Xe+ bombardment at normal incidence displayed satisfactory agreement with previously published data over an energy range of 200 eV–1 keV. For Xe+ ions, the dependence of the yields on angle of incidence θ was determined for 0° ≤ θ ≤ 80°. Over this range, an increase in C sputtering yield by a factor of 4.8 was observed, with the peak in yield occurring at 70°. This is a much higher variation compared to Xe+ → Mo yields under similar conditions, a difference that may be attributed to higher scattering of the incident particles transverse to the beam direction than in the case of Xe+ → C. In addition, the variation of the yields with θ was not strongly energy dependent. Trapping of Xe in the surface was observed, in contrast to observations using the QCM technique with metallic target materials. Finally, target surface roughness was characterized using atomic force microscope measurements to distinguish between the effects of local and overall angle of incidence of the target.
Keywords: Sputtering; QCM; Thin film; Ion beam; Carbon;
Effect of interfacial diffusion on microstructure and properties of FePt/B4C multifunctional multilayer composite films by F.J. Yang; H. Wang; H.B. Wang; X. Cao; Q. Li; M.J. Zhou (2516-2520).
FePt/B4C multilayer composite films were prepared by magnetron sputtering and subsequent annealing in vacuum. By changing Fe layer thickness of [Fe/Pt]6/B4C films, optimal magnetic property (8.8 kOe and remanence squareness is about 1.0) is got in [Fe(5.25 nm)/Pt(3.75 nm)]6/B4C sample whose composition is Fe rich and near stoichiometric ratio. The characterizations of microstructure demonstrate that the diffusion of B and C atoms into FePt layer depends strongly on B4C interlayer thickness. When B4C interlayer thickness of [Fe(2.625 nm)/Pt(3.75 nm)/Fe(2.625 nm)/B4C]6 films is bigger than 3 nm, stable value of grain size (6–6.5 nm), coercivity (6–7 kOe) and hardness (16–20 GPa) is observed. Finally, the multifunctional single FePt/B4C composite film may find its way to substitute traditional three-layer structure commonly used in present data storage technology.
Keywords: Magnetron sputtering; Vacuum annealing; Multifunction; Multilayer composite film; Magnetic recording;
Polypropylene surface modification by entrapment of polypropylene-graft-poly(butyl methacrylate) by H.J. Chen; X.H. Shi; Y.F. Zhu; Y. Zhang; J.R. Xu (2521-2527).
Surface modification of polypropylene was carried out by entraping a copolymer of polypropylene grafted poly(butyl methacrylate) into polypropylene. The effects of structure of copolymers, contact die and content of modifiers on their surface enrichment were studied by attenuated total reflection infrared spectroscopy (ATR-FTIR), contact angle measurements and scanning electron microscopy (SEM). The results indicated that PPw-g-PBMA could diffuse preferably onto the surface and effectively increase the hydrophilicity of PP. Lower content and higher surface energy die were in favor of the copolymer to enrich on the PP surface. PPw-g-PBMA with low PBMA contents, short length of PBMA distributed in PP with smaller phase domains and favored its selective enrichment on the surface of PP, especially at lower loadings in blends. The modified material exhibited excellent solvent-resistance.
Keywords: Polypropylene; Polypropylene-graft-poly(butyl methacrylate); Macromolecular surface modifier; Blend surface modification; ATR-FTIR;
Influence of annealing temperature on the nanostructure and corrosivity of Ti/stainless steel substrates by K. Khojier; H. Savaloni; H. Kangarloo; M. Ghoranneviss; M. Yari (2528-2533).
Titanium films of 80 nm thickness were deposited on stainless steel type 304, and they were post-annealed under flow of oxygen at different temperatures. The prepared samples were corrosion tested in 1.0 M H2SO4 solution using potentiodynamic and galvanometric polarization technique. The variation of corrosion resistance of these samples showed that the optimum annealing temperature is 473 K. The reduction of corrosion resistance of the sample with increasing the temperature above 473 K is attributed to the phenomena which are confirmed by AFM results: (a) increase of surface roughness, and (b) formation of larger grains with large grooves between them on the film surface. Hence larger effective surfaces for chemical reactions are provided. The films’ crystallographic and morphological structures were analysed using XRD and AFM, respectively before corrosion test and SEM after corrosion test. It is observed that the crystallographic structure of the film goes through a sudden change at 943 K annealing temperature and three phases of titanium oxide (i.e., rutile, anatase and brookite) are formed.
Keywords: Ti/stainless steel films; Annealing; Potentiodynamic and galvanometric techniques; Corrosion; XRD; AFM; SEM;
Embedded structure of silicon monoxide in SiO2 films by Kiyoshi Chiba; Yoshihito Takenaka (2534-2539).
The structure of SiO x (x = 1.94) films has been investigated using both X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The SiO x films were deposited by vacuum evaporation. XPS spectra show that SiO1.94 films are composed of silicon suboxides and the SiO2 matrix. Silicon clusters appeared only negligibly in the films in the XPS spectra. Si3O+ ion species were found in the TOF-SIMS spectra with strong intensity. These results reveal the structure of the films to be silicon monoxide embedded in SiO2, and this structure most likely exists as a predominant form of Si3O4. The existence of Si–Si structures in the SiO2 matrix will give rise to dense parts in loose glass networks.
Keywords: SiO x films; Silicon suboxides; X-ray photoelectron spectroscopy; Secondary ion species; Time-of-flight secondary ion mass spectrometry;
Surface structure and energy of B2 type intermetallic compound NiAl by Jian-Min Zhang; Dou-Dou Wang; Guo-Xiang Chen; Ke-Wei Xu (2540-2543).
The surface structure and energies for 22 surfaces of NiAl, an ordered intermetallic compound of B2 structure, have been studied by using embedded atom method. The results show that, for alternating Ni and Al surfaces with odd numbers of the sum of their three Miller indices, the energy difference between the Ni terminated surface and Al terminated surface increase linearly with increasing the interlayer distance. So from surface energy minimization, the Al terminated surface is favorable for each alternating Ni and Al surface. This is in agreement with experimental results. However, the energy of the (1 1 0) surface belonged to the other kind of the surface consisted of stoichiometric atomic layers and with even numbers of the sum of their three Miller indices, is the lowest in all two kinds of the surfaces. Therefore the (1 1 0) texture of NiAl appears mostly in the experiments.
Keywords: Intermetallic compound; NiAl; Surface structure; Surface energy; EAM;
Electron field emission from a patterned array of diamond-like carbon on anodic aluminum oxide template by C. Li; X.C. Li; E.M. Chong; P.J. Zhang; X.Y. Fan; P.X. Yan (2544-2547).
A patterned array of diamond-like carbon (DLC) was grown on anodic aluminum oxide (AAO) template by filtered cathodic arc plasma (FCAP) technique at room temperature. The diameters of patterned array of DLC were ∼150 nm, and the patterned array density was estimated to ∼109 cm−2. A broad asymmetric band ranging from 1000 cm−1 to 2000 cm−1 was detected by Raman spectrum attributed to characteristic band of DLC. The fraction of sp3 bonded carbon atoms of the patterned array of DLC was measured by X-ray photoelectron spectrum (XPS) and the ratio was about 62.4%. Field emission properties of the patterned array of DLC were investigated. A low turn-on field of 3.4 V/μm at 10 μA/cm2 with an emission area of 3.14 mm2 was achieved. The results indicated that the electrons were emitted under both the effect of enhanced field because of the geometry and the work function of the DLC sample. Based on Fowler–Nordheim plot, the values of work function for the patterned array of DLC were estimated in range of 0.38 to 1.75 from a linearity plot.
Keywords: Field emission; Diamond-like carbon; Filtered cathodic arc plasma; Anodic aluminum oxide template;
Surface morphology of laser tracks used for forming the non-smooth biomimetic unit of 3Cr2W8V steel under different processing parameters by Zhihui Zhang; Hong Zhou; Luquan Ren; Xin Tong; Hongyu Shan; Xianzhou Li (2548-2555).
Aiming to form the high quality of non-smooth biomimetic unit, the influence of laser processing parameters (pulse energy, pulse duration, frequency and scanning speed in the present work) on the surface morphology of scanned tracks was studied based on the 3Cr2W8V die steel. The evolution of the surface morphology was explained according to the degree of melting and vaporization of surface material, and the trend of mean surface roughness and maximum peak-to-valley height. Cross-section morphology revealed the significant microstructural characteristic of the laser-treated zone used for forming the functional zone on the biomimetic surface. Results showed that the combination of pulse energy and pulse duration plays a major role in determining the local height difference on the irradiated surface and the occurrence of melting or vaporization. While frequency and scanning speed have a minor effect on the change of the surface morphology, acting mainly by the different overlapping amount and overlapping mode. The mechanisms behind these influences were discussed, and schematic drawings were introduced to describe the mechanisms.
Keywords: Surface morphology; Laser processing parameters; Non-smooth biomimetic unit; 3Cr2W8V steel;
Fabrication, magnetism and high frequency application of exchange-coupled Fe65Co35±2–SiO1.7±0.2 granular films by Dongsheng Yao; Xueyun Zhou; Huaping Zuo; Bangmin Zhang (2556-2561).
A series of (Fe65Co35±2) x –(SiO1.7±0.2)1−x nano-granular films with various metal volume fractions (x) were fabricated by rf sputtering. In a wide range, excellent soft magnetic properties have been achieved. In the x range from 0.7 to 0.48, the films exhibit small coercivity H c not exceeding 4 Oe and high electrical resistivity ρ up to 1.15 × 104 μΩ cm. And a minimum H c value of 1.65 Oe was obtained for the sample of x = 0.57 with ρ = 2.86 × 103 μΩ cm. At a frequency lower than 2.0 GHz, the real part μ′ of complex permeability of this sample is more than 170 and the FMR frequency is as high as 2.6 GHz, implying a high cut-off frequency for high frequency applications. With decreasing Fe65Co35±2 volume fraction, the resistivity of films increases remarkably and the grain size decreases obviously. At the same time, the coercivity H c decreases with grain size decreasing, which is consistent with the conclusion resulted from random anisotropy model quoted by Herzer. Study on Henkel plots shows that intergranular ferromagnetic exchange coupling exists among grains and is important for realizing soft magnetic properties.
Keywords: Nano-granular films; Soft magnetic properties; Henkel plot; Exchange coupling; High frequency application;