p-Type doping of diamond films with a novel organoboron source

p-Type polycrystalline diamond films were prepared by hot-filament CVD method using a liquid cyclic organic borinate ester as the doping source. The obtained films were identified as diamond films by means of SEM and Raman spectroscopy. The resistivity of the doped films can be adjusted by changing the temperature of the boron source.     

密封容器中后处理制备Tl2Ba2CaCu2Oy高温超导薄膜及其性能研究

以铝酸镧（001）单晶为基片，采用两步法制备Tl2Ba2CaCu2Oy（Tl 2212）高 温超导薄膜.首先，利用脉冲激光沉积（PLD）工艺沉积Ba2CaCu2Ox非晶前驱体薄膜；然后，前驱体薄膜在高温（720—850℃）下密封钢容器里铊化结晶形成Tl 2212薄膜.XRD结果表明Tl2212 薄膜是沿c轴方向生长的，其相组成为Tl 2212，摇摆曲线（0012）的半高宽为0.72° ，SEM图像显示其表面光滑平整，其零电阻温度为106.2K. 关键词： Tl 2212超导薄膜 脉冲激光沉积     

Bi底层对FePt薄膜的影响

利用磁控溅射的方法，在玻璃基片上制备了以Bi为底层的FePt薄膜，经不同温度真空热处理得到L1₀-FePt薄膜.研究了Bi做底层对FePt薄膜的有序化温度及矫顽力H_c的影响.实验结果表明：以Bi做底层的FePt薄膜在350℃实现低温有序，同时其H_c也有大幅度提高，并且可以在更大成分范围内获得H_c较高的L1₀-FePt薄膜.利用X射线光电子能谱研究了薄膜中Bi原子的分布情况，利用X射线衍射研究了薄膜的晶体学结构变化.结果表明,Bi底层在退火过程中的扩散促进了FePt薄膜有序度的升高. 关键词： 0-FePt薄膜')" href="#">L1₀-FePt薄膜 有序化温度 底层 扩散     

Evanescent wave spectroscopy of methylene blue solutions at surfaces using a continuum generated by a nonlinear fiber

The way organic thin films properties are affected by molecular interactions at surfaces is an important research topic because thin molecular films constitute a model system for biological research and have applications ranging from light-emitting diodes and solar cells to chemical sensors. In this work, the formation of thin films of Methylene Blue in aqueous solution at a fused quartz surface was investigated with evanescent wave absorption spectroscopy, using a continuum spectrum generated in a non-linear fiber by short laser pulses.     

Casimir force with the inclusion of a finite thickness of interacting plates

The Casimir force between two thin metal films is calculated with allowance made for a finite thickness of the films and a finite plasma frequency. The conditions are determined under which the Casimir force in the films can be weakened considerably (by at least one order of magnitude) as compared to massive metal plates. A comparison with the available experimental data is performed and the conclusion is drawn that the observed values of the Casimir force for the films can be explained in terms of the existing theory under the assumption that the wavelength of plasma oscillations in real films is larger than 1000 nm.     

Fractal structure of films deposited in a tokamak

The surface of amorphous films deposited in the T-10 tokamak was studied in a scanning tunnel microscope. The surface relief on a scale from 10 nm to 100 μm showed a stochastic surface topography and revealed a hierarchy of grains. The observed variety of irregular structures of the films was studied within the framework of the concept of scale invariance using the methods of fractal geometry and statistical physics. The experimental probability density distribution functions of the surface height variations are close in shape to the Cauchy distribution. The stochastic surface topography of the films is characterized by a Hurst parameter of H = 0.68–0.85, which is evidence of a nontrivial self-similarity of the film structure. The fractal character and porous structure of deposited irregular films must be considered as an important issue related to the accumulation of tritium in the ITER project. The process of film growth on the surface of tokamak components exposed to plasma has been treated within the framework of the general concept of inhomogeneous surface growth. A strong turbulence of the edge plasma in tokamaks can give rise to fluctuations in the incident flux of particles, which leads to the growth of fractal films with grain dimensions ranging from nano-to micrometer scale. The shape of the surface of some films found in the T-10 tokamak has been interpreted using a model of diffusion-limited aggregation (DLA). The growth of films according to the discrete DLA model was simulated using statistics of fluctuations observed in a turbulent edge plasma of the T-10 tokamak. The modified DLA model reproduces well the main features of the surface of some films deposited in tokamaks.     

Laser damage mechanism of porous Al2O3 films prepared by a two-step anodization method

Pure aluminum films were deposited on a B270 glass by electron beam evaporation technique. These aluminum films, which were used as anode, were put in sulfuric acid and oxalic acid to prepare porous alumina films using a two-step anodization method. The microstructure and laser damage characteristics of the alumina films were then tested. Results show that the microstructure of the alumina films formed in sulfuric acid and oxalic acid were vertical (cylindrical) pores with different diameters. The laser-damaged spot of the porous films was formed by innumerable small damaged pits with no mutual influence. Films prepared in different acids reveal different damage characteristics and reflect different mechanisms.     

Comparison of ZnO thin films grown on a polycrystalline 3C-SiC buffer layer by RF magnetron sputtering and a sol-gel method

Zinc oxide (ZnO) thin films were deposited on a polycrystalline (poly) 3C-SiC buffer layer using RF magnetron sputtering and a sol-gel method. The post-deposition annealing was performed on ZnO thin films prepared using both methods. The formation of ZnO piezoelectric thin films with less residual stress was due to a close lattice mismatch of the ZnO and SiC layers as obtained by the sputtering method. Nanocrystalline, porous ZnO film prepared using the sol-gel method showed strong ultraviolet UV emission at a wavelength of 380 nm. The 3C-SiC buffer layer improved the optical and piezoelectric properties of the ZnO film produced by the two deposition methods. Moreover, the different structures of the ZnO films on the 3C-SiC intermediate layer caused by the different deposition techniques were also considered and discussed.     

Formation of uniaxial molecular films by liquid-crystal imprinting in a magnetic field

Scanning tunneling microscopy was used to study molecular order in monolayer organic films formed by solution-phase growth from thermotropic liquid crystal solvents. The films develop macroscopically uniaxial alignment, with adlayer orientation controlled by an external magnetic field through interactions mediated by the liquid crystal. Results are presented for two films deposited from nematic and smectic- A solvents, along with a discussion of the alignment mechanism.     

Fabrication and characterization of nanocrystalline Al,Co:ZnO thin films by a sol–gel dip coating

The consequence of annealing on the micro-structural and electrochemical characteristics of Al doped CoZnO thin films deposited by sol–gel dip coating technique are studied. X-ray diffraction indicates that films have a hexagonal wurtzite structure oriented towards the (100). Optical properties of films are recorded by transmission curves utilising a UV–VIS spectrophotometer. The investigation of the optical transmission spectra indicates that the band gap of the films decrease from 3.99 eV to minimum 3.83 eV upon annealing. All films show room temperature ferromagnetism whose magnetization increases with annealing. Dip coated films possess polycrystalline nanosized grains with porous morphology.     

Ferroelectricity of lanthanum-modified lead titanate thin films obtained by a diol-based sol-gel method

Lanthanum-modified lead titanate thin films have been prepared by a diol-based sol-gel method from precursor solutions with a growing excess of PbO. The films were crystallized with thermal treatments at 650 °C and heating rates of 10 °C  min^-1 and higher than 500 °C min^-1 by direct insertion in a pre-heated furnace. The structure, microstructure, and composition of the films were studied by grazing-incidence X-ray diffraction, electron microscopies, and energy-dispersive X-ray spectroscopy. A 20 mole % excess of PbO must be included in the precursor solution in order to compensate PbO volatilization occurring during the thermal treatment and, thus, obtain single-phase perovskite-type structure films. Non-textured porous films were obtained when a 10 °C min^-1 rate is used, whereas [001]/[100] oriented films without porosity were obtained when rapid heating was used. Dielectric permittivity, ac current density, hysteresis loops, and switching curves were measured in the films. Values of remanent polarization and coercive field are comparable to those reported for similar films. The effects on the ferroelectric properties of an electrical and a post-crystallization thermal treatments were characterised. Received: 5 January 1998 / Accepted: 20 November 1998 / Published online: 17 March 1999     

Method of envelopes for studying a two-film system on a reflecting substrate

For determining the optical constants and the thickness of thin films (including strongly absorbing films) by the spectrophotometric method, we propose to deposit them on intermediate films formed on strongly reflecting substrates. Due to this, an interference pattern depending on the optical constants and the thickness of the film under study will be observed in the reflectance spectrum. The method of envelopes of the extrema in the reflectance spectrum that is based on the iterative approach is developed for studying two-film systems.     

Resonances of thermally stimulated electromagnetic excitations of thin films on a substrate in a near field

The spectral features of thermally stimulated electromagnetic excitations generated by films of wide band gap semiconductors on metals in vacuum at different distances from a sample surface were investigated. Special attention was given to the interaction of characteristic resonances in the excitation spectrum of these fields with local vibrations of Cd impurity atoms inside ZnTe films on metal substrates.     

Superior tribological properties of an amorphous carbon film with a graphite-like structure

Amorphous carbon films with high sp² concentrations are deposited by unbalanced magnetron sputtering with a narrow range of substrate bias voltage. Field emission scanning electron microscopes (FESEMs), high resolution transmission electron microscopes (HRTEMs), atomic force microscopes (AFMs), the Raman spectrometers, nano-indentation, and tribometers are subsequently used to characterize the microstructures and the properties of the resulting films. It is found that the present films are dominated by the sp² sites. However, the films demonstrate a moderate hardness together with a low internal stress. The high hardness of the deposited film originates from the crosslinking of the sp² clusters by the sp³ sites. The presence of the graphite-like clusters in the film structure may be responsible for the low internal stress. What is more important is that the resulting films show excellent tribological properties with high load capacity and excellent wear resistance in humid atmospheres. The relationship between the microstructure determined by the deposition condition and the film characteristic is discussed in detail.     

Surface properties of platinum thin films as a function of plasma treatment conditions

We examined the surface properties of platinum (Pt) thin films exposed to oxygen and argon plasma treatments and compared them to as-deposited Pt films. The surface wetting properties, refractive index and extinction coefficient of the Pt films were monitored as a function of time after different plasma treatments. Surfaces treated with an oxygen plasma were dramatically different from as-deposited Pt, whereas argon plasma treated surfaces were similar to as-deposited films. X-ray photoelectron spectroscopy confirmed the formation of platinum oxide on films treated with an oxygen plasma, while such oxide diminished after argon plasma treatment. Surface morphology studied with atomic force microscopy indicated a strong dependence of the surface roughness of the Pt films on the power and duration of the argon plasma used for the treatment. Based on these studies, an oxygen plasma treatment followed by a brief low-power argon plasma etch was developed for the purpose of regenerating clean and metallic Pt surfaces, and at the same time providing the smoothest possible surface morphology.     

Low-temperature MOVPE growth of ZnO thin films by using a buffer layer

ZnO thin films have been grown on a-plane (1,1,−2,0) sapphire substrates by metalorganic vapor phase epitaxy (MOVPE) at low substrate temperature of 350 °C. It is showed that the crystal and electrical quality of the thin films was improved by using a ZnO buffer layer. The photoluminescence (PL) measurements indicate that the ZnO thin films grown at such a low substrate temperature have a strong UV emission.     

Active damping of a micro-cantilever piezo-composite beam

Thick PZT films are of major interest in the actuation of mechanical structures. One of the promising fields deals with active damping. Since it is a dynamic application, hard-PZT type of screen-printed films are suited to this kind of use. Nevertheless, the drop in dielectric, ferroelectric and piezoelectric properties induced by the fabrication process is a serious constraint and it needs to be evaluated. The first section of this paper will present the mechanical system used for the experimental investigations. These investigations look to quantify the electromechanical properties of the films once the deposition process is achieved. The experimental observations highlighting the efficiency of hard-PZT thick films in active damping despite the drop in the electromechanical properties will then be considered. The control strategy used in the experiments can be called pseudo-direct-velocity feedback. Then the constitutive relations of the composites will be needed to derive the roots locus analysis by means of finite element modelling on one hand and through the roots of the partial derivative equations on the other hand. The unconditional stability of the uncollocated system will be demonstrated and its typical asymptotic behavior when the gain tends towards infinity will be explained.     

Anomalously high low-frequency effective permittivity in a system of metal nanoislands

The low-frequency effective permittivity in a system of Co, W, and FeNi metal nanoislands in an electric field is investigated. The permittivity of films is determined from analyzing the dependences of the susceptance of the films on the temperature and the electric field. It is found that the effective permittivity of the structures under investigation has an anomalously high positive value (10⁷–10⁸) and that an increase in the electric field leads to a decrease in the effective permittivity and an increase in the electrical conductivity of the films. The nature of the high effective permittivity of the structures is governed by the island structure of the metal films and associated with the polarization of dipoles formed by pairs of negatively and positively charged metal nanoislands.     

一种获得半导体薄膜光学参数的方法

实现薄膜光学参数的简便测量对于薄膜的制备和应用具有重要意义。引入适用于半导体材料的Forouhi_Bloomer模型,用其表征薄膜折射率与色散的关系。考虑到粗糙度的影响,假设薄膜厚度服从正态分布,给出了模拟退火法与迭代法相结合、由可见光光谱测定薄膜光学参数的方法。作为尝试,以硅系薄膜为例进行了计算。结果表明,获得的厚度与用椭偏仪测量的结果较为吻合。该方法适用于研究和测量半导体薄膜的光学性能和膜厚,具有很高的实用价值。     

Structural properties of TiN films grown on stainless steel substrates by a reactive radio-frequency sputtering technique at low temperature

TiN thin films were grown on stainless steel substrates by using the reactive radio-frequency magnetron-sputtering technique at relatively low temperature (200°C) using Ti and N₂. The deposition rate of the TiN film increased linearly with increasing applied radio-frequency power, and it decreased with increasing partial-pressure ratio of the N₂ gas to the Ar gas. Scanning electron microscopy (SEM) showed that the surfaces of the TiN films had very smooth morphologies. The TiN thin film had good stoichiometry for a partial-pressure ratio of 0.05. The stoichiometry of the TiN films and the interface qualities of the TiN/stainless steel heterostructures were investigated by Auger electron spectroscopy (AES) measurements. Auger depth profiles indicated that the compositions of the as-grown films consisted of titanium and nitrogen uniformly distributed throughout the films and that the films exhibited smooth interfaces. The interface quality of the TiN films to the stainless steel substrates were improved by annealing. These results indicate that annealed TiN thin films grown on stainless steel substrates hold promise for potential applications in advanced ceramic devices.