In_（0．2）Ga_（0．8）As／GaAs应变多量子阱结构的光调制反射和热调制反射谱的研究

对Ｉｎ（０．２）Ｇａ（０．８）Ａｓ／ＧａＡｓ应变多量子阱在７７Ｋ下的光调制反射谱（ＰＲ）和热调制反射谱（ＴＲ）进行了实验研究．对ＰＲ结果的线形拟合指认了应变多量子阱中子能级的跃迁，并与理论计算结果作了比较．实验对比确认ＰＲ中１１Ｈ、１３Ｈ等跃迁结构为非耦合态、具有电场调制机构的一阶微商性质．而１１Ｌ、３１Ｈ、２２Ｈ等跃迁结构为阶间耦合态，对这些隧穿耦合的低场调制产生三阶微商特性．     

非晶硅基薄膜的等离子体刻蚀光发射谱检测

本文研究了采用锁定放大相干检测技术的等离子体光发射谱检测系统。用该系统检测了仅用CF4作为刻蚀气体刻蚀非晶硅基薄膜的等离子体光发射谱。分析了检测结果和刻蚀机理。     

Plasma immersion ion implantation for SOI synthesis: SIMOX and ion-cut

We have demonstrated feasibility to form silicon-on-insulator (SOI) substrates using plasma immersion ion implantation (PIII) for both separation by implantation of oxygen and ion-cut. This high throughput technique can substantially lower the high cost of SOI substrates due to the simpler implanter design as well as ease of maintenance. For separation by plasma implantation of oxygen wafers, secondary ion mass spectrometry analysis and cross-sectional transmission electron micrographs show continuous buried oxide formation under a single-crystal silicon overlayer with sharp Si/SiO₂ interfaces after oxygen plasma implantation and high-temperature (1300°C) annealing. Ion-cut SOI wafer fabrication technique is implemented for the first time using PIII. The hydrogen plasma can be optimized so that only one ion species is dominant in concentration and there are minimal effects by other residual ions on the ion-cut process. The physical mechanism of hydrogen induced silicon surface layer cleavage has been investigated. An ideal gas law model of the microcavity internal pressure combined with a two-dimensional finite element fracture mechanics model is used to approximate the fracture driving force which is sufficient to overcome the silicon fracture resistance.     

a—Si等离子体刻蚀的研究

将等离子体刻蚀应用于非晶硅的刻蚀中,得到边缘整齐、分辩率高、重复性好、图形清晰的满意效果。通过调整工艺条件,可严格控制刻蚀速率。其特点优于湿式化学腐蚀,是一种非晶硅特性研究和器件制造中值得推广和使用的方法。     

硅中硼离子注入校准样品的研制

本文主要介绍了硅中硼离子注入校准样品的制备与研究。分别用三台SIMS仪器对样品进行了深度剖析与比对,并对用作校准目的的样品主要参数进行了定值。     

Formation of titanium and cobalt germanides on Si (100) using rapid thermal processing

Titanium and cobalt germanides have been formed on Si (100) substrates using rapid thermal processing. Germanium was deposited by rapid thermal chemical vapor deposition prior to metal evaporation. Solid phase reactions were then performed using rapid thermal annealing in either Ar or N₂ ambients. Germanide formation has been found to occur in a manner similar to the formation of corresponding silicides. The sheet resistance was found to be dependent on annealing ambient (Ar or N₂) for titanium germanide formation, but not for cobalt germanide formation. The resistivities of titanium and cobalt germanides were found to be 20 μΩ-cm and 35.3μΩ-cm, corresponding to TiGe₂ and Co₂Ge, respectively. During solid phase reactions of Ti with Ge, we have found that the Ti₆Ge₅ phase forms prior to TiGe₂. The TiGe₂ phase was found to form approximately at 800° C. Cobalt germanide formation was found to occur at relatively low temperatures (425° C); however, the stability of the material is poor at elevated temperatures.     

Microstructure of Silicon Carbide Whiskers Synthesized by Carbothermal Reduction of Silicon Nitride

The microstructure of silicon carbide whiskers synthesized by carbothermal reduction of silicon nitride has been studied using transmission electron microscopy. All of the whiskers examined are single crystals, and grow in the (111) crystallographic direction. Two different forms of stacking faults and microtwins were observed; in one the planar defects are normal to the whisker growth direction, and the other has the defect planes at an angle of about 70° to the growth axis, while both forms of the defects are on the [111] closed-packed planes. Without the addition of catalyst, droplets containing metallic impurities were not found at the tips of the whiskers synthesized by the present process. A core and outer regions were observed in the single-crystal whiskers, which may be evidence that the whiskers were formed by a two-stage mechanism.     

醋酸甲酯在Cs_(1.5)PW/SiO_2催化剂上的水解反应

通过改变阳离子的种类与配比,制备了一系列SiO2负载的磷钨酸盐催化剂,考察了制备方法对催化剂性能的影响,采用傅里叶变换红外光谱、X射线衍射、X射线荧光光谱、环境扫描电子显微镜等方法对催化剂进行了表征,并考察了该系列催化剂对醋酸甲酯水解反应的活性。实验结果表明,Cs1.5PW/SiO2催化剂的活性最好,当Cs1.5PW负载量(质量分数)为30%时,Cs1.5PW的Keggin结构保持完好,没有硅钨酸阴离子形成,Cs1.5PW在SiO2载体上高度分散;在反应温度55℃、反应时间2h的条件下,醋酸甲酯的转化率为35.79%,约为均相磷钨酸催化剂的1.3倍。该催化剂重复使用4次后,醋酸甲酯的转化率稳定在25%;80℃下反应2h,与NKC-9磺酸树脂催化剂相比,醋酸甲酯的转化率提高了5.17%。     

大型预焙铝电解槽使用碳化硅砖与普通碳砖复合块的探讨

碳化硅砖和碳化硅砖与普通碳砖复合侧块，在上世纪末期我国铝电解槽上开始推广应用。使用后各厂家普遍发现碳化硅砖及碳化硅砖与普通碳块复合侧块均出现不同程度的断裂、上抬和脱落现象，该文对断裂、上抬和脱落原因进行了分析，并提出了改进措施。     

Oxidation behavior of silicide coating on Ti3SiC2-based ceramic

A silicide coating was prepared on Ti₃SiC₂-based ceramic by pack cementation to improve the oxidation resistance of Ti₃SiC₂, which is a technologically important material for high temperature applications. The microstructure, phase composition and oxidation resistance of the coated sample were investigated. The results demonstrated that the silicide coating was mainly composed of TiSi₂ and SiC. A single layer of a mixture of SiO₂ and TiO₂ was formed on the surface of the coated sample during isothermal oxidation at 1100 °C and 1200 °C for 20h. Compared to Ti₃SiC₂, the parabolic rate constant of silicide coated Ti₃SiC₂ decreased by 2~3 orders of magnitude. Furthermore, the coated sample showed much better cyclic oxidation resistance than Ti₃SiC₂ during the cyclic oxidation at 1100 °C for 400 times. However, during the preparation of the coating, a number of fine cracks formed in the outer layer of the coating. When these cracks penetrated the whole coating during the cyclic oxidation, the oxidation rate was accelerated, which degraded the oxidation resistance. Electronic Publication