Influence of laser treatment on the electrical properties of plasma-enhanced-atomic-layer-deposited TiO2 thin films

TiO₂ dielectric films with 38 nm thickness were grown on Si (100) substrates at 200°C by plasma-enhancedatomic-layer deposition. Laser-irradiated TiO₂ films maintained an amorphous phase similar to as-grown films and showed an increase in permittivity and leakage current density with increasing laser powers and the number of laser shots at constant laser power. Laser-irradiation of TiO₂ films at room temperature produced oxygen vacancies at the film surface and new Ti³⁻ valences. The electrons and space charges produced through the defect chemistry increased the leakage current density and permittivity in laser-irradiated TiO₂ films, respectively. The dielectric and electrical properties of the laser-irradiated TiO₂ films were completely recovered to correspond with those of as-grown films by post-annealing at 300°C for 5 min in O₂ ambient.     

Chemical deposition of CuInSe2 thin films by photoelectrochemical applications

Copper indium diselenide films have been synthesized by chemical bath deposition method. The configuration of fabricated cell is n-CuInSe₂|NaOH (1 M) + S (1 M) + Na₂S (1 M)|C_(graphite). The photoelectrochemical cell characterization of the films is carried out by studying current-voltage characteristics in dark, capacitance-voltage in dark, barrier height measurements, power output, photoresponse and spectral response. The study shows that CuInSe₂ thin films are n-type conductivity. The junction ideality factor is found to be 3.81. The flat band potential is found to be 0.763 V. The barrier height value is found to be 0.232 eV. The study of power output characteristic shows open circuit voltage, short circuit current, fill factor and efficiency are found to be 310 mV, 20 μA, 42.12% and 0.82%, respectively. Photoresponse shows lighted ideality factor which is 2.92. Spectral response shows the maximum current observed at 650 nm.     

Influence of heat treatment and surface engineering on thermal fatigue behaviour of tool steel

Abstract

Thermal fatigue (TF) is a common problem in many tool steel components. It is caused by thermal cycling in presence of internal constraints. The resulting thermomechanical stresses induce thermal cracking (heat checking). A laboratory test was developed to reproduce TF damage on a laboratory scale, under oxidizing conditions. Two different test configurations were used to induce unidirectional and bidirectional cracking. Nitriding impairs TF resistance of plain steel due to the easier propagation of cracks through the diffusion layer. The efficacy of PVD coatings is dependent on their oxidation resistance and microstructure. The higher oxidation resistance of AlCrN/AlTiN than CrN results in delayed crack initiation. TF resistance is increased if the coating is free of defects and the interface adhesion is good.     

Influence of galvanised surface state on the duplex systems behaviour

The influence of galvanised surface conditions on the duplex systems behaviour is analysed. A paint system was applied over new and weathered galvanised steel samples. A comparative study was performed by adhesion tests and electrochemical impedance spectroscopy (EIS) technique. Previously, the roughness profiles of galvanised surfaces were evaluated. The obtained results point out that a certain weathering degree is necessary for optimum adherence between paint and metallic surface and for good corrosion protection. Nevertheless, when the weathering degree is too high, the protection efficiency decreases. This behaviour can be explained in terms of galvanised surface roughness. The smooth surface of fresh galvanised steel makes difficult the establishment of adhesive bonds at coating-metal interface, leading to poor behaviour, at initial stages. If the weathering degree is too high, the surface roughness can hinder optimum coverage by the organic coating and the passive layer remains partially bare; as a consequence, the protection features are lower than those obtained for an average weathering degree where good adhesion and complete coverage are reached.     

Micro-porous TiO2 thin films grown on surface of Ti substrate

Microporous titanium dioxide thin films have been grown on titanium plates by the micro-plasma oxidation method with different current densities (4, 6, 10 and 14 A/dm2). X-ray diffraction, scanning electronic microscopy and UV-Vis spectrophotometry were used to characterize the films. It is found that the films grown are microporous and consist of crystalline titanium dioxide. The micropore size and the content of anatase and rutile TiO2 phase increase with the applied voltage. The relatively higher degradation efficiency for rhodamine B is obtained in the film produced with a current density of 10 A/dm2.     

焙烧温度对K2Ti6O13薄膜光电化学和光催化的影响

采用溶胶凝胶法在导电玻璃上制备K2Ti6O13薄膜,考察焙烧温度对薄膜结构和光催化、光电化学行为的影响。采用XRD和AFM测定晶体和表面结构;以自组装在薄膜表面的十八烷基三氯硅烷（OTS）为光催化降解对象,评价K2Ti6O13薄膜光催化氧化性能;通过计时电位,循环伏安和光电流表征薄膜中光生载流子行为。结果表明,合适的结晶度和晶粒尺寸的匹配使500℃焙烧的K2Ti6O13薄膜具有较高的载流子激发、分离和迁移能力,体现出最高的光催化氧化能力和最大的光电流,光催化性能优于TiO2薄膜。由光电测试计算得其在254 nm光照下光电量子效率约为6.9%。     

Influence of surface treatment on detachment of anodic films from Al–Mg alloys

Previous work of the authors has revealed detachment of anodic films during anodizing of electropolished, solid-solution Al–3 at.%Mg alloy at constant current density, with the possibility of the electropolishing pre-treatment having a significant influence on the loss of the film material. Here, anodic films were formed on a similar alloy, with pre-treatment by electropolishing, alkaline etching or mechanical polishing. The results disclose the detachment of the anodic film for all pre-treatments, thus demonstrating that prior electropolishing is not essential for initiation of detachment. However, the occurrence of detachment was sensitive to the current density, with lower current densities promoting detachment at earlier stages of growth of the anodic film for a particular pre-treatment.     

Influence of intermittently etching on quality of CVD diamond thin films

A new method, called growing-etching repetitional process based on hot filament chemical vapor deposition, was proposed to improve the quality of diamond film. During the deposition carbon source was intermittently closed letting hydrogen etch the surface of the diamond film fi＇om time to time. In order to find whether it is helpful to the films＇ quality, a series of experiments were done. The results show that the new method can enhance the orientation of the chemical vapor deposition diamond films, reduce the graphite phase and increase the film＇s surface resistivity.     

Influence of heat treatment and gamma-rays irradiation on the structural and optical characterizations of nano-crystalline cobalt phthalocyanine thin films

Thin films of nano-crystalline cobalt phthalocyanine (CoPc) were prepared by thermal evaporation technique under high vacuum at room temperature and were identified by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The prepared films were divided into three groups for study; the first was the as deposited films, the second was heat treated under vacuum for 1 h at 630 K, and the third group was irradiated in gamma cell type ⁶⁰Co source in air at room temperature with total absorbed dose of 150 kGy. The optical properties for the three groups were investigated using spectrophotometric measurements of the transmittance and reflectance at normal incidence of light in the wavelength range from 200 to 2500 nm. The optical constants, refractive index, n, and absorption index, k, were calculated and found to be independent of film thickness in the measured film thickness range. The dispersion energy, E_d the oscillator energy, E₀ and the high frequency dielectric constant, ?_∞ of the three groups were obtained. The energy band model was applied and the types of the optical transitions responsible for optical absorption were found to be indirect allowed transition. The onset and optical energy gaps were calculated. Discussion of the obtained results and their comparison with the previously published data were also given.     

Influence of post-grown treatments on CuInS2 thin films prepared by sulphurization of Cu-In films

Polycrystalline CuInS2 (CIS) films were prepared by sulphurization of Cu-In films.The surface morphology and phase composition of the as-grown film,the KCN-etched film,and the annealed KCN-etched film were investigated.During the sulphurization,the secondary CuχS phase segregated on the surface of the as-grown films.To improve the crystalline quality of CulnS2 films,a series of post-grown treatments,such as KCN-etching and vacuum annealing KCN-etched films,were performed on the as-grown films.Both as-grown and post-treated films were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),and energy dispersive spectroscopy (EDS).The results indicated that a CuχS secondary phase segregated on the surface of the as-grown film,which could be removed effectively by KCN etching.After the vacuum annealing treatment,the KCN-etched film had a sphalerite structure with (112) preferred orientation.Meanwhile,the crstalline quality of the CIS film was significantly improved,which provided a novel method to improve the performance of thin film solar cells.     

The thickness of thin surface films determined by photo-electron spectroscopy

The thickness of inhibitive films formed on copper surfaces immersed in solutions of benztriazole (BTA) have been estimated by three methods based on X-ray photo-electron spectroscopy and compared with the results from a fourth method using the electrical capacitance of such films. All but one of the methods show that the film thickness increases with time of immersion and range in thickness between 1 and 3 nm for immersion times of minutes to several hours. The limitation and accuracy of each method are discussed.     

The application of thin layer surface activation to the study of erosion-corrosion behaviour

Thin layer surface activation is a technique in which the surface layers of a material are made radioactive by high energy charged particle bombardment. The resulting activity distribution as a function of depth within the surface is well defined, and consequently measurement of the activity loss from the material provides a means of monitoring any surface loss which has occurred. The application of this technique to the measurement of erosion-corrosion losses from mild steel specimens under boiler feedwater conditions is described, and further possibilities for its application are discussed.     

磁控溅射SiC薄膜表面形貌演化行为研究

采用射频磁控溅射法在石英玻璃基底上沉积SiC薄膜.用扫描电子显微镜(SEM)和原子力显微镜( AFM)观察薄膜的表面形貌,利用粗糙度和颗粒度大小对薄膜表面形貌动态演化进行量化表征.结果表明:在100～175 W溅射功率范围内,1 000℃高温真空退火处理能明显减小SiC薄膜表面粗糙度,膜层表面更为平滑,颗粒大小更为均匀...     

Influence of solution pH in electrodeposited iron diselenide thin films

Thin films of iron diselenide (FeSe₂) have been prepared on indium doped tin oxide coated conducting glass (ITO) substrates from an aqueous electrolytic bath containing FeSO₄ and SeO₂. Growth mechanism has been analyzed using cyclic voltammetry. The potential region in which the formation of FeSe₂ occurs is found to be −450 mV versus SCE. X-ray diffraction analysis showed that the deposited films are found to exhibit orthorhombic structure with preferential orientation along (1 2 0) plane. X-ray line profile analysis has been carried out to determine the microstructural parameters such as crystallite size, rms microstrain, dislocation density and stacking fault probability. Surface morphology and film composition have been analyzed using scanning electron microscopy, atomic force microscopy and energy dispersive analysis by X-rays, respectively. Optical parameters such as band gap, refractive index, extinction coefficient, real and imaginary dielectric constants, dielectric susceptibility and optical conductivity have been determined from optical absorption measurements. The observed results are discussed in detail.     

Influence of nitrogen doping on thermal stability of fluorinated amorphous carbon thin films

Nitrogen doping fluorinated amorphous carbon （α-C ： F） films were deposited using radio frequency plasma enhanced chemical vapor deposition （RF-PECVD） and annealed in Ar environment in order to investigate their thermal stability. Surface morphology and the thickness of the films before and after annealing were characterized by AFM and ellipsometer. Raman spectra and FHR were used to analyze the chemical structure of the films. The results show that the surface of the films becomes more homogeneous either by the addition of N2 or after annealing. Deposition rate of the films increases a little at first and then decreases sharply with the increase of N2 source gas flux. It is also found that the fraction of aromatic rings structure increases and the thermal stability of the films is strengthened with the increase of N2 flux. Nitrogen doping is a feasible approach to improve the thermal stability of α-C ： F films.     

Formation of nanoislands on the surface of thin dipeptide films under the effect of vaporous organic compounds

Sorption properties of a thin L-alanyl-L-valine dipeptide film for vapors of organic compounds, i.e., methanol and toluene, were studied. Compositions of the inclusion compounds formed in the systems are determined using quartz microbalances. The surfaces morphology of of thin dipeptide films before and after the interaction with organic sorbate was studied with atomic force microscopy. The dipeptide was found to have a larger sorption capacity for methanol than for toluene. As a result of the interaction between a thin L-alanyl-L-valine dipeptide layer with toluene vapor, nanoislets appear on the film surface, and the receptor ability of dipeptide inactivated.     

Influence of impurities in aluminium on surface treatment

The origin of grain orientation dependent textures on a surface treated aluminium Al-0.2% Mg alloy has been probed by atomic force microscopy, transmission electron microscopy and elemental depth profiling by radio frequency glow discharge optical emission spectroscopy. Magnesium cations are observed to act as a tracer species, assisting definition of the residual alumina film thickness, developed by pretreatment. Copper impurities, enriching in the alloy immediately below the alumina film, act as a marker, assisting definition of the alloy/film interface. Conversely, the absence of iron and silicon in the depth profiles, present in the alloy as impurities at similar levels to copper, suggests their role in the development of the texture. Such elements are considered to be present in the alloy as fine segregates; their location at alloy ridges defines the positions of cathodic sites, with the adjacent matrix undergoing dissolution through the residual alumina film during pretreatment.