电子辐照诱发固态相变导致的氮化硼纳米结构生长

报道了N+离子轰击产生的氮化硼(BN)纳米结构,及在电子辐照时结构演化的高分辨透射电子显微镜的原位测定结果.应当强调的是,这种类富勒烯和发夹结构的演化,实际上是电子辐照诱发固态相变的发展,观察中发现的一些BN颗粒、卷曲物,可以被认为是类富勒烯等纳米结构形成的前体或早期阶段.提出了一种类富勒烯等结构的电子辐照动力学模型,并进行了讨论. 关键词： 氮化硼 电子辐照 透射电子显微镜 氮化硼纳米形成物     

氮化铝薄膜的光学性能

分别使用X衍射仪和紫外（190 nm～800 nm）分光光度仪,测量了用分子束外延法生长在SiC（001）基底面上的AIN薄膜的X衍射、透射谱和不同温度下的吸收谱.X衍射表明:实验所用的AIN薄膜在c-轴存在应变和应力，该应变和应力主要是由于AIN的晶格常量与基底SiC的晶格常量不匹配所致.透射谱表明:AIN薄膜的禁带宽度大约为6.2eV；而其对应的吸收谱在6.2eV处存在一个明显的台阶,此台阶被认为是AIN薄膜中的带边自由激子吸收所产生,忽略激子的结合能(与禁带宽度相比),则该值就对应为AIN的禁带宽度.而其对应的不同温度下（10 k～293 k）的吸收谱的谱线的形状和位置无明显的变化表明:温度对AIN薄膜的禁带宽度亦无明显的影响，这主要是由于在AIN薄膜中存在着应力所致.     

过氧聚钨酸薄膜上光栅的制备

用过氧聚钨酸（PPTA）水溶液，通过离心涂膜法在显微镜载玻片上制备了具有光滑表面且厚度为100nm的PPTA薄膜，利用PPTA薄膜在紫外光照下可研制光栅以及其它光学元件的薄膜材料，具有很高的利用价值。     

Interpretation of initial stage of 3C-SiC growth on Si(1 0 0) using dimethylsilane

The initial stage of cubic silicon carbide (3C-SiC) growth on a Si(0 0 1) surface using dimethylsilane (DMS) as a source gas was observed using scanning tunneling microscopy (STM) and reflection high-energy electron diffraction (RHEED). It was found that the dimer vacancies initially existing on the Si(0 0 1)-(2 × 1) surface were repaired by the Si atoms in DMS molecules, during the formation of the c(4 × 4) surface. From the STM measurement, nucleation of SiC was found to start when the Si surface was covered with the c(4 × 4) structure but before the appearance of SiC spots in the RHEED pattern. The growth mechanism of SiC islands was also discussed based on the results of RHEED, STM and temperature-programmed desorption (TPD).     

Temperature effect on deposition rate of silicon nitride films

Temperature effects on deposition rate of silicon nitride films were characterized by building a neural network prediction model. The silicon nitride films were deposited by using a plasma enhanced chemical vapor deposition system and process parameter effects were systematically characterized by 2⁶⁻¹ fractional factorial experiment. The process parameters involved include a radio frequency power, pressure, temperature, SiH₄, N₂, and NH₃ flow rates. The prediction performance of generalized regression neural network was drastically improved by optimizing multi-valued training factors using a genetic algorithm. Several 3D plots were generated to investigate parameter effects at various temperatures. Predicted variations were experimentally validated. The temperature effect on the deposition rate was a complex function of parameters but N₂ flow rate. Larger decreases in the deposition rate with the temperature were only noticed at lower SiH₄ (or higher NH₃) flow rates. Typical effects of SiH₄ or NH₃ flow rate were only observed at higher or lower temperatures. A comparison with the refractive index model facilitated a selective choice of either SiH₄ or NH₃ for process optimization.     

A microprocessor based autoscanner for electromigration studies in thin films

Mass transport due to electromigration can be estimated if the diffusion coefficientD and the electromigration effective charge numberZ* are known. Neutron activated tracer scanning method determine the radioactivity at different positions. An automatic scanning system for determining the radioactive concentration profiles developed using a microprocessor is described in this paper. Using the radioactive concentration profiles the electromigration shift is determined. From this shift the electromigration effective charge numberZ* is calculated. The system developed was tested for tin thin films.     

基片光学特性对薄膜光强透过谱的影响

在考虑基片与空气界面反射率以及基片吸收不能忽略的情况下，对常见的基片上薄膜的光强透过率公式进行了修正，导出了该情况下的透过率公式．以非晶硅薄膜为研究对象，采用模拟计算说明基片光学特性对薄膜光强透过谱的影响．     

FeCoB-SiO2磁性纳米颗粒膜的微波电磁特性

采用交替沉积磁控溅射工艺制备了超薄多层的FeCoB SiO2 磁性纳米颗粒膜 .利用x射线衍射仪、扫描探针显微镜、透射电子显微镜分析了薄膜的微结构和形貌特征 .采用振动样品磁强计、四探针法、微波矢量分析仪及谐振腔法测量薄膜试样的磁电性能和微波复磁导率 .重点对SiO2 介质相含量、薄膜微结构对电磁性能产生重要影响的机理做了分析和探讨 .结果表明 :这类FeCoB SiO2 磁性纳米颗粒膜具有良好的软磁性能和高频电磁性能 ,2GHz时的磁导率 μ′高于 70 ,可以应用于高频微磁器件或微波吸收材料的设计     

Interaction of indigo carmine dye with silica modified with humic acids at solid/liquid interface

Two distinct humic acids, one extracted from Brazilian peat soil, HA_PS, and another one obtained from commercial source, HA_FL, were attachment onto silica gel modified with aminopropyltrimethoxysilane, producing two material named SiHA_PS and SiHA_FL, respectively. The ability of these materials in removing indigo carmine dye from aqueous solution was followed through series of adsorption isotherms adjusted to modified Langmuir equation. The maximum number of moles adsorbed gave 6.82 ± 0.12 × 10⁻⁴ and 2.15 ± 0.17 × 10⁻⁴ mol g⁻¹ for SiHA_PS and SiHA_FL, respectively. Same interactions were calorimetrically followed and the thermodynamic data showed endothermic enthalpic values: 12.31 ± 0.55 and 24.69 ± 1.05 kJ mol⁻¹ for SiHA_PS and SiHA_FL surfaces, respectively. Gibbs free energies for two adsorption processes of indigo carmine dye presented negative values, reflecting dye/surface interactions must be accompanied by an increased in entropy values, which are 65 ± 3 and 98 ± 5 J mol⁻¹ K⁻¹ for SiHA_PS and SiHA_FL materials, respectively. The adsorption processes for both materials were spontaneous in nature although they presented an endothermic enthalpy for the interaction, resulting in an entropically favored process.