Phonon Scattering Study of Strain-Effects in Heterostructure.

在本次联合研究中，最重要的是要克服一些关键问题或困难，即：(1)精确控制热脉冲高频声子的产生；(2)高灵敏度和快速的声子检测；(3)制备良好控制的siGe系统薄膜；(4)正确的数据积累和精确的分析；(5)在电子器件中的应用。(1)采用新的方法和设计，利用光刻技术制备了高频声子产生加热器，以获得高时间和空间分辨率。提出了一种将0.5 mmphi的同轴电缆连接到加热器和测辐射热计的新技术，以避免电磁穿入探测器。(2) 10nm厚的铝薄膜测热计在5*10^<-6> Torr的氧气氛中蒸发，在1.35 K处具有陡峭的宽/线性过渡斜率，灵敏度远高于以往报道。在晶体学上发现了更多的六边形结构，这是第一次观察到的，也是本项目的显著成果之一。利用涡轮分子泵和新型光刻工艺，在无油真空条件下获得了良好的再现性和优良的质量。(3)采用射频溅射法制备了SiGe系统薄膜，在应变边界处观察到较强的模式转换。但由于电导率不足以满足EEMT的要求，因此HEMT材料需由日立等实验室提供。(4)从理论角度出发，Miyasato和Wigmore与Lacaster大学的A G Kozorezov一起进行了计算，我们模拟了粗糙表面热脉冲的散射，即上文提到的反射实验。用正交近似计算了长程不规则性的影响。如上所示，本项目的技术和理论研究在高频声子与其中极薄薄膜和/或电子的相互作用领域，即低维电子气体方面取得了重大突破。少

The most important points in the present joint research is that some essential problems or difficulties should be overcome, which are : (1) precisely controlled heat pulse high frequency phonon generation and (2) high sensitive and quick phonon detection, (3) preparation of good controlled siGe system films, (4) correct data accumulation and their precise analyzes, and their (5) application to electronic devices.(1) The heater wihch generates high frequency phonons was prpared by photolithography technology with new method and design to get high resolution in time and space. A new technique to connect coaxial cable of 0.5 mmphi to the heater and the bolometer was developed and to avoid the electro-magnetic brake-through into the dtector.(2) The aluminium thin film bolometer of 10nm thick was evaporated in 5*10^<-6> Torr of oxgen atmosphere, wihch has steep and wide/linear transition slope at 1.35 K,and its sensitivity is far higher than that reported in the past. The crystallographic s … More tructure was revealed to be hexagonal, which is the first obervation and one of remarkable results of the present project. A good reproducibility and its outstanding quality were obtained in oil-free vacuum by turbo-molecular pump andby new photolithography technique by positive-resist process.(3) SiGe system film was prepared by RF-sputtering method, and a strong mode conversion at strained boundary was observed. But showed that the electric conductivi-tiy was not enough for EEMT,then the materials for HEMT is to be offered by HITACHI and other laboratories.(4) From the theoretical point, Miyasato and Wigmore developed calculation with A G Kozorezov at Lacaster University, in which we have modelled the scattering of heat pulse from rough surface, as reflection experiment as mentioned above. The effect of long-range irregu-larities was calculated in the eikonal approximation.As shown above, the technological and theoretical researches of the present project have made a great break-through in the field of interaciton of high frequency phonons with very thin films and/or electrons in it, namely low dimensional electron gas. Less