楔形薄膜逾渗系统的临界特性

报道一种楔形金属薄膜逾渗系统的制备方法和测量结果,这种新型逾渗系统具有独特的非线性I-V特性和临界规律,从实验中发现:在这一各向异性系统中,普适标度关系仍然成立,分析表明:这些特性是由于该系统中随空间坐标而变化的跳跃电导效应而引起的. 关键词：     

感染生长模型的逾渗模拟

在规则格子点阵中，活跃点逐步动态地以可变概率感染附近空缺点而生成系综.利用感染概率替代系综温度，给粒子划分能级，可以用巨正则系综配分函数表征体系.蒙特卡洛方法模拟验证了该体系在逾渗阈值处的相变行为.提出了一种新的较为普适的估算规则点阵逾渗阈值的方法.对介质基底上金属薄膜的实验研究验证了该感染生长模型的合理性.由此给出了格子点阵的固有属性(逾渗)如何在粒子聚集成团簇这一动态过程中体现出来的物理模型. 关键词： 逾渗 系综 蒙特卡洛方法 生长模型     

无规分形衬底上银膜逾渗系统的交流特性

通过对沉积在具有无规自相似结构的α-Al₂O₃断裂面上的银薄膜逾渗系统交流特性的测量,证明了在逾渗阈值p_c附近这一系统的交流电导率和介电常数满足指数临界规律和普适标度关系。还给出了这种逾渗系统的电容与直流电阻的关系,并对其意义作了讨论。 关键词：     

ZnO压敏陶瓷电导研究的新方法

在-180?℃—100?℃温度范围内研究了ZnO-Bi₂O₃二元、ZnO-Bi₂O₃-MnO三元以及商用ZnO压敏陶瓷的I-V特性.研究发现：二元试样电导由散射电导串联构成;三元试样电导由热电子发射电导混联构成;商用试样电导由热电子发射电导和隧道效应电导并联构成.对整个电流范围内的电导拟合表明：通过同一温度下电导分量同电流的关系,可以计算出该部分电导对应的非线性指数.在商用试样中,隧道电流产生的非线性指数为33,与实测值接近;该隧穿分量在小电流区也存在,且在低温下表现地更为明显. 关键词： ZnO压敏陶瓷 I-V特性')" href="#">I-V特性 导电机理     

用SiCl4/H2气源沉积多晶硅薄膜光照稳定性的研究

对以SiH₄/H₂及SiCl₄/H₂为源气体、采用 等离子体增强化学气相沉积技术制备的非晶硅薄膜和多晶硅薄膜进行了光照稳定性的研究.实验表明，制备的多晶硅薄膜并没有出现 非晶硅中的光致衰减现象，其光电导、暗电导在光照过程中没有下降反而有所上升且电导率 变化快慢受氢稀释度的制约.多晶硅薄膜的光照稳定性可能来源于高的晶化度及Cl元素的存在. 关键词： 多晶硅薄膜 稳恒光电导效应 晶界 光致衰退效应     

光照和偏压对微晶硅薄膜室温电导的影响

报道了SiCl₄/H₂等离子体化学气相沉积方法制备的未掺杂微晶硅薄 膜，在短时间光照或加上直流偏压后其室温暗电导随时间缓慢变化的行为. Raman散射谱结 果表明，薄膜的晶态体积比大于70%. 暗电阻的实验结果显示: 材料具有弱的持久光电导效 应；薄膜的暗电导在外加直流电场的作用下缓慢上升，电场反向后出现暗电导的恢复过程， 而且暗电导变化速度与偏压大小和温度有关. 根据异质结势垒模型，指出外加条件下载流子 的空间分离和重新分布以及材料非均匀性造成的势垒是引起电导 关键词： 微晶硅 电导率 薄膜     

栅氧化层介质经时击穿的逾渗模型

在研究了MOSFET栅氧化层介质经时击穿物理机制的基础上，提出了氧化层击穿的逾渗模型.认为氧化层的击穿是E′心和氧空位等深能级缺陷产生与积累，并最终形成电导逾渗通路的结果.指出在电场作用下，氧化层中产生深能级缺陷，缺陷形成定域态，定域态的体积与外加电场有关.随着应力时间的增长，氧化层中的缺陷浓度增大，定域态之间的距离缩小.当定域态之间的距离缩小到一个阈值时，定域态之间通过相互交叠形成逾渗通路，形成扩展态能级，漏电流开始急剧增大，氧化层击穿. 关键词： 栅氧化层 TDDB 逾渗 模型     

非磁性半导体异常磁电阻效应的有效介质理论

有效介质理论自洽方程被用来研究非磁性半导体材料的异常磁电阻效应. 通过建立两组分无序电导网络,同时引入组分的霍尔效应,计算了体系的有效电导张量随磁场和组分浓度的变化关系.结果表明,当两种组分具有不同类型的载流子时,体系中各组分零场电阻的差异将导致在垂直磁场和平行磁场方向上产生异常的磁电阻效应.这些宏观的磁电阻效应来源于体系中的非均匀性,并与组分的几何逾渗结构具有明显的关联. 关键词： 异常磁电阻效应 非磁性半导体 有效介质近似     

二维孔隙裂隙双重介质逾渗规律研究

在孔隙介质逾渗理论的基础上，将另外一个非常重要的渗透通道——裂隙引入到介质的逾渗研究中，提出了更为普遍的孔隙裂隙双重介质的逾渗研究方法.通过对二维平面孔隙裂隙双重介质的数值计算，得到了孔隙裂隙双重介质三个重要参数：孔隙率，裂隙分形维数、裂隙数量分布初值与逾渗概率的关系，给出了孔隙裂隙双重介质逾渗阈值的数学表达式，揭示了孔隙裂隙双重介质的逾渗规律. 关键词： 孔隙 裂隙 双重介质 逾渗 逾渗阈值     

STM中量子点接触的电导计算

采用模式匹配和散射矩阵方法，对扫描隧道显微镜(STM)中量子点接触过程中的电导进行了计算.结果表明由量子点接触形成的纳米结构的电导呈现量子化特征，这种量子化现象随所形成的纳米结构的横向尺寸和锥角的减小而增强.而且在半导体材料中比金属中更易观察到电导量子化现象. 关键词： STM 量子点接触 量子化电导     

楔形Al薄膜的物理特性

采用真空蒸镀方法,利用液体衬底在沉积过程中的扩散,形成了沉积在玻璃表面的楔形铝薄膜,并研究了它的结构和I-V特性.实验表明,楔形铝薄膜的斜率仅10^-6—10^-7,具有与一般非平整薄膜不同的I-V特性,其非平整效应不能用普通的非平整薄膜的RRN理论模型来解释. 关键词： 楔形铝薄膜     

Photoluminescence of amorphous carbon films fabricated by layer—by—layer hydrogen plasma chemical annealing method

A method in which nanometre-thick film deposition was alternated with hydrogen plasma annealing (layer-by-layer method) was applied to fabricate hydrogenated amorphous carbon films in a conventional plasma-enhanced chemical vapour deposition system.It was found that the hydrogen plasma treatment could decrease the hydrogen concentration in the films and change the sp^2/sp^3 ratio to some extent by chemical etching.Blue photoluminescence was observed at room temperature,as a result of the reduction of sp^2 clusters in the films.     

Pulsed laser treatment of gold and black gold thin films fabricated by thermal evaporation

The effect of pulsed laser treatment of metal, and metal blacks, was studied. Gold and black gold thin films were fabricated by thermal evaporation of gold in a vacuum and nitrogen atmosphere respectively. Black gold films were grown in a nitrogen atmosphere at pressures of 200 Pa and 300 Pa. UV pulsed laser radiation (λ = 266 nm, τ = 4 ns), with fluence ranging from 1 mJ·cm⁻² to 250 mJ·cm⁻² was used for the film treatment in a vacuum and nitrogen atmosphere. The nitrogen pressure was varied up to 100 kPa. Surface structure modifications were analyzed by optical microscopy, atomic force microscopy (AFM) and scanning electron microscopy (SEM). Energy dispersive X-ray spectroscopy (EDX) was used for chemical characterization of the samples. A significant dependence of the film optical and structural properties on laser treatment conditions (laser fluence, ambient pressure and number of applied pulses) was found. The threshold for observable damage and initiation of changes of morphology for gold and black gold surfaces was determined. Distinct modifications were observed for fluences greater than 106 mJ·cm⁻² and 3.5 mJ·cm⁻² for the gold and black gold films respectively. Absorbtivity of the black gold film is found to decrease with an increase in the number of laser pulses. Microstructural and nanostructural modifications after laser treatment of the black gold film were observed. EDX analysis revealed that no impurities were introduced into the samples during both the deposition and laser treatment.      

大面积六硼化镧薄膜阴极制备及性能

 采用电子束蒸发方法在大面积玻璃基底和钽基底上沉积六硼化镧薄膜阴极。分别对玻璃基底上沉积的六硼化镧薄膜的生长取向、附着力与不同蒸发角度(0°, 30°,45°和60°)的关系进行了研究;对钽基底上沉积的六硼化镧薄膜阴极的逸出功进行了研究。结果表明:在基底温度为250 ℃时,制备的六硼化镧薄膜具有(100)晶面择优生长的特点;蒸发角度为45°时,六硼化镧薄膜(100)晶面的晶格常数与靶材相差最小,晶粒较小;根据优化的工艺制备的六硼化镧薄膜阴极的逸出功为2.56 eV。     

Electroluminescence of double-doped diamond thin films

A new electroluminescence device is fabricated by microwave plasma chemical vapour deposition system and electron beam vapour deposition system. It is comprised of highly doped silicon/diamond/boron/nitrogen-doped diamond/indium tin oxide thin films. Effects of process parameters on morphologies and structures of the thin films are detected and analysed by scanning electron microscopy, Raman spectrometer and x-ray photoelectron spectrometer. A direct-current (DC) power supply is used to drive the electroluminescence device. The blue light emission with a luminance of 1.2 cd·m 2 is observed from this double-doped diamond thin film electroluminescence device at an applied voltage of 105 V.     

Enhancement of deposition rate of titanium silicon oxide films on silicon using hexafluorotitanic acid by nitric acid

The deposition of titanium silicon oxide films on silicon using hexafluorotitanic acid and boric acid as sources is much enhanced by nitric acid incorporation. The deposition delay time is almost zero. The structure of the films is titanium silicon oxide examined by Fourier transform infrared spectrometer. By current-voltage measurement, the leakage current of the as-deposited film with a thickness of 458 Å is about 7.78×10^-6 Å/cm² at the electrical field of 1 MV/cm. By capacitance-voltage measurement, the effective oxide charge of the as-deposited film is 6.31×10¹⁰ cm^-2. The static dielectric constant and refractive index are about 13 and 1.98, respectively. Compared with that without nitric acid incorporation, the lower effective oxide charge is from a sharp interface due to in-situ etching of nitric acid. The higher leakage current is from the higher deposition rate and the higher dielectric constant is from higher titanium content. PACS 77.84.-s     

Simulation of polycrystalline 3D film growth: An investigation of the evolution of grain size and texture in diamond films

An analytical method for simulating gas phase film growth has been developed and used to study the growth of diamond films during prolonged deposition, i.e. the film thickness is much larger than the lateral grain size. From a model system composed of 10⁴ grains, reliable results can be evaluated for the growth of diamond films by (111) and (001) deposition under different initial conditions and with varying growth parameters. It is demonstrated that the rate of structure evolution is sensitively influenced by the aspect ratio of diamond crystal. A near-linear proportionality between the average grain size and the thickness of films can be approximately yielded for a large film thickness which is about 10 times of the average distance of the nuclei. The proportionality constant varies for a statistical nucleation from 0.0056 to 0.43 by changing the aspect ratio. Furthermore, the orientational distribution is drastically narrowed down so that the probability of coalescence of grains with a slight orientational difference is considerably increased. Received: 28 September 2000 / Accepted: 19 February 2001 / Published online: 3 May 2001     

Characteristics of High In-Content InGaN Alloys Grown by MOCVD

InN and In0.46 Ca0.54N films are grown on sapphire with a CaN buffer by metalorganic chemical vapour deposition （MOCVD）. Both high resolution x-ray diffraction and high resolution transmission electron microscopy results reveal that these films have a hexagonal structure of single crystal. The thin InN film has a high mobility of 4 75 cm^2V^-1s^-1 and that oflno.46 Gao.54N is 163 cm^2 V^-1s^-1. Room-temperat ure photoluminescence measurement of the InN film shows a peak at 0.72eV, confirming that a high quality InN film is fabricated for applications to full spectrum solar cells.     

MAPLE deposition of PEG:PLGA thin films

We report on MAPLE deposition of thin films of PEG:PLGA blends. The films were analyzed in terms of morphology, chemical composition, wettability, and optical constants. These properties were particularly discussed in correlation with film thickness. The film thickness was increased by increasing the deposition rate (i.e., laser fluence). This method was effective for fluences up to 1 J/cm², above which the efficiency of the deposition leveled off. Moreover, with increasing fluence above 1 J/cm², important changes in the polymeric films were noticed: the surface roughness increased abruptly (up to ∼200 nm), the polymers lost their chemical integrity and their optical constants underwent significant changes. In addition, surface wettability decreased considerably, water contact angle reaching ∼90°; this was attributed to increased surface roughness and to orientation of the hydrophobic groups toward the surfaces of the films. An alternative method for obtaining thicker films was employed, by prolonging the deposition time while maintaining a constant, relatively low, deposition rate (i.e., fluence). In this case, the properties of the films were significantly less affected.     

Modulation of residual stress in diamond like carbon films with incorporation of nanocrystalline gold

Residual stress modulation in the diamond-like carbon coatings with incorporation of gold nanoparticles was studied critically. The films were deposited on glass and Si (1 0 0) substrates by using capacitatively coupled plasma chemical vapor deposition. Stresses in the films were determined from the broadening of the optical absorption tail and were found to decrease from 2.3 GPa to 0.48 GPa with increasing gold content (2-7 at.% Au) in the DLC matrix. Gold incorporation also made the films harder than the corresponding DLC coatings. Modulation of stress with nanocrystalline gold content in the DLC matrix was related to the relative amount of sp²/sp³ content in the DLC films.