Fabrication of Semiconductor Nanostructured New Materials and Applications to Functional Devices

1.纳米结构Ge、Si新材料的制备与表征利用本课题组开发的团束蒸发技术，成功地制备出尺寸均匀的Ge、Si团簇。令人惊讶的是，这些团簇的晶体结构已经转变为它们的高压相，如ST-12(Ge)和BC-8(Si)：新的结构被用各种技术包括高分辨电子显微镜，x射线光电子能谱等研究。研究发现，只有在长时间(10天)的高压下，才会发生从金刚石到ST-12的相变。此外，块状Ge中的高压形式是亚稳定的，这与其中ST-12结构在高达700ﾟC.2下稳定的纳米结构形成了鲜明的对比。将SiO_x纳米结构应用于低介电常数材料气相蒸发法制备的ULSiSiO_x纳米结构薄膜具有很低的介电常数(小于1.9)。这意味着这种材料是未来超大规模集成电路层间绝缘材料的极佳候选材料。这一发明申请了一项专利。由多层掺硅玻璃薄膜组成的光学谐振腔的制作一种新的制备方法，可以形成高反射率的多层光学反射镜。多层膜是在薄膜沉积过程中溅射的射频功率调制作用下形成的。利用由多层膜和金属反射镜组成的法布里-珀罗谐振器，从镶嵌在SiO_2玻璃中的Si纳米颗粒的宽可见光发射中获得了相对较窄的光谱。

1. Fabrication and Characterization of Nanostructured Ge and Si New MaterialsThe cluster-beam evaporation technique developed by our group was succesfully utilized to fabricate Ge and Si clusters with excellent size uniformity. Surprisingly, the crystal structures of those clusters have been transformed to their high pressure phases such as ST-12(Ge) and BC-8(Si) : The new structures were investigated by various techniques including the high resolution transmission electron microscopy, x-ray photo-elctron spectroscopy, etc.A high pressure up to 80kbar was applied to crystalline Ge flakes to form the bulk ST-12 structure. It was found that the phase transformation from the diamond to ST-12 occurs only when the specimen is kept at the high pressure for a long period (ten days). Furthermore, the high pressure form in bulk Ge was meta-stable, showing a striking contrast to the nanostructures in which the ST-12 structure is stable in up to 700ﾟC.2. Application of SiO_x Nanostructures to A Low Dielectric Constant Material in ULSISiO_x Nanostructured films fabricated by the gas-evaporation technique shows a very low dielectric constant(less than 1.9). This means that this material is an excellent candidate for the future interlayer insulating material for ULSI.A patent was applied to this invension.3. Fabrication of Optical Resonator Composed of Multi-Layered Si-Doped Glass FilmsA new fabrication method was developed to form a multi-layered optical mirror with high reflectivity. The multi-layer was formed by the rf-power modulation of the sputtering during the film deposition. Relatively narrow spectra were obtained from a broad visible light emission from Si nano-particles embedded in the SiO_2 glass, using a Fabri-Perot resonator composed of the multi-layer and metal reflectors.