A study of textured non-stoichiometric MoTe2 thin films used as substrates for textured stoichiometric MoS2 thin films

Textured MoTe₂ films have been prepared by sequential evaporation of the constituents followed by annealing under a tellurium pressure. The films are systematically textured with the c-axis of the crystallites perpendicular to the plane of substrate, however, the film composition is difficult to control and even after process optimization the films are tellurium deficient. This is thought to be caused by the electro negativity difference of the constituents.The textured MoTe₂ films have been used as substrates on which to grow MoS₂ films by annealing under a pressure of sulfur that allows textured MoS₂ films to be grown with good crystalline properties. The presence of sulfur at the surface and annealing under dynamic vacuum is important for this process and moreover, suppresses the superficial oxidation of the Mo and Te constituents.     

Structural and electrical properties of evaporated ZnTe thin films

Zinc telluride thin films of various thicknesses are deposited by vacuum evaporation onto glass substrates at room temperature. The X-ray diffraction technique is used to determine the crystalline structure and grain size of the films, respectively. The structure was found to be cubic with preferential orientation along a (1 1 1) plane and crystallite size of about 50-80 nm. The degree of preferred orientation and crystallite size are increased as the film thickness increases. The current density-voltage (J-V) characteristics showed ohmic conduction in the lower voltage range and space-charge-limited conductivity in the higher voltage range. Capacitance measurements indicated that the films have a relative permittivity, ε_r, of approximately 8.19. Further evidence for this conduction process was provided by linear dependence of V_t on d². Analysis of the results yielded hole concentration , which is correlated with the structural properties.     

Studies on polycrystalline Cd0.96Zn0.04Te thin films prepared by vacuum evaporation

Polycrystalline Cd_0.96Zn_0.04Te thin films are deposited onto glass substrates (Corning 7059) kept at room temperature by vacuum evaporation. The films exhibit zinc blende structure with predominant (1 1 1) orientation. The rms roughness of the films evaluated by atomic force microscope is 3.7 nm. The band gap energy of the films measured by optical transmittance measurement is 1.539 eV. The photoluminescence (PL) spectrum of the films shows intense emission due to free and bound exciton recombination and no emission associated with crystal imperfection and PL line shapes give indications of the high quality of the layers. These films have been implanted with properly mass analyzed Boron ions (¹⁰B⁺) and the effect of implantation has been analyzed by X-ray diffraction, Raman scattering and optical transmittance measurements and the results are explained on the basis of the implantation induced surface roughness and lattice disorder.     

溶胶-凝胶薄膜的制备和应用

概述了溶胶—凝胶薄膜的制备方法和在各个领域的应用。并对溶胶—凝胶薄膜制备的基本原理、制备过程中薄膜质量的影响因素和存在的问题进行了探讨和总结。     

Studies on the electronic transport properties of some organic semiconductors in thin films

The investigated compounds are some derivatives of orthotolidin-N,N-bis (4-aminobenzene-2-sulphonic) acid. The temperature dependences of the electrical conductivity and Seebeck coefficient are studied on the thin films deposited from dimethylformamide solution onto glass substrates. It is known that the investigated compounds have typical semiconducting properties. The values of some important parameters of the films (thermal activation energy of electrical conduction, concentrations and mobilities of charge carriers) have been determined. The correlations between some of these parameters and molecular structure of the respective compounds are discussed.     

The Frictional Properties of Thin Inorganic Halide Films on Iron Measured in Ultrahigh Vacuum

Friction coefficients are measured in ultrahigh vacuum using a tungsten carbide tribopin against thin films of sodium chloride and potassium iodide deposited onto clean iron. It is found, in accordance with previous measurements for potassium chloride on iron, that the friction coefficient falls from an initial value of 2 for the clean iron surface to a minimum value after a few tens of Ångstroms of the halide have been deposited onto the surface, and remains constant for thicker films. The minimum friction coefficient is independent of applied load and therefore obeys Amontons' law. Simple theories for the effect of a low-shear-strength film suggest that the friction coefficient should depend on the shear strength of the film. This idea is tested by plotting the minimum friction coefficient versus the hardness of the film material, which is proportional to its shear strength, where a linear correlation was found. The lack of dependence of friction coefficient with film thickness for thicker films implies that ploughing forces do not contribute significantly to the friction coefficient.     

Temporal Evolution of Normal Hot Spots in Current-Driven Superconducting Films

In addition to the critical current I_c (T), which generates Phase-Slip Centers (PSCs), thin superconducting films possess a well-defined second limiting current I_h, or current intensity able to maintain a preestablished hot spot. By pulsing step functions of the current and monitoring the voltage response on the nanosecond scale, we have determined (T I_c) and (T I_h). From a dynamic study of the two main modes of dissipation in YBCO and Nb films, it is concluded that PSCs are stable structures in current-biased bridges. In contrast, hot spots grow at a constant rate of a few tens of meters per second, determined by the thermal diffusivity of the material and by its bolometric response time. On reducing the current from I_h, the so-called healing length, or minimum normal length, was found, of the order of 0.2 m in YBCO and 2 m in Nb. In summary, the experiment provides three independent measurements (PSC nucleation time, velocity of growth, and minimum length) for only two parameters (D and ).     

Memory characteristics of Au/PZT/BIT/p-Si ferroelectric diode

A ferroelectric memory diode consisting of Au/PZT/BIT/p-Si multilayer configuration has been fabricated by pulsed laser deposition (PLD) technique. The ferroelectric properties and the memory characteristics are investigated. The P-E curve of the PZT/BIT/p-Si films system had an asymmetry saturated hysteresis loop with P, = 15 μC/cm2 and Ec = 48 kV/cm, and the decay in remanent polarization was only 10% after 109 switching cycles, meanwhile the increase in coercive field was 12% . The C-V hysteresis loop and the I-V curve showed a memory effect derived from the ferroelectric polarization of PZT/BIT films, and the current density was 6.7 × 10-8 A/cm2 at a voltage of + 4V. Our diode had nonvolatile and nondestructive memory readout operation. There was a read current disparity of 0.05 μA for logic "1" and logic "0" at a read voltage of + 2V, and the stored logical value ("1" or "0") could be read out in 30 min.     

TiO2-CeO2离子储存电极薄膜的制备与性能研究

采用溶胶-凝胶技术，以Ti（OC489）4和Ce（NO3）3·6H2O为前驱体制备了Ti／Ce不同摩尔配比的TiO2-CeO2复合薄膜。运用X射线衍射（XRD）、扫描电镜（SEM）、紫外-可见光吸收光谱、循环伏安法和电化学交流阻抗等分析了其结构和性能。实验结果表明，当Ti／Ce摩尔比为1：1时，薄膜具有致密的非晶态显微结构；在Li^＋离子注入，脱出过程中，薄膜有较快的电化学响应和较高的电荷容量，在20mV·s^-1的扫描速率下，注入Li^＋离子的扩散系数约为1．50×10^-11cm^2·s^-1，并且第20次稳定循环的阴极和阳极电荷密度分别为12和9．5mC·cm^-2，表明薄膜具有良好的循环可逆性。电化学和光学测试表明该薄膜可以作为电致变色装置的对电极。     

氮化ZnO/Ga2O3薄膜合成GaN纳米管

利用射频磁控溅射法在Si(111)衬底上先溅射ZnO中间层,接着溅射Ga2O3 薄膜,然后ZnO/Ga2O3薄膜在管式炉中常压下通氨气进行氮化,高温下ZnO层在氨气的气氛中挥发,而Ga2O3薄膜和氨气反应合成出GaN纳米管.X射线衍射(XRD)测量结果表明利用该方法制备的GaN具有沿c轴方向择优生长的六角纤锌矿结构.利用傅里叶红外光谱(FTIR)研究了所制备样品的光学性质.利用透射电子显微镜(TEM)和选区电子衍射(SAED)观测了样品的形貌和晶格结构.