Preparation and Characterization of Si-based Manmade Crystals

用SiH_2Cl2和H原子研究了Si在(111)面上的原子层外延(ALE)的生长特性。碰撞气相生成SiHCl径向是获得理想的单层/周期生长速率的关键，并且存在合适的气压和停留时间来密集生成SiHCl径向。对于(100)表面，H原子可以刻蚀化学吸附在表面的SiCl分子，氢压应保持在较低的水平。基于这些结果，在(100)和(111)面上都获得了较宽的ALE温度窗口，在(100)和(111)面上用GeH_2(CH3)_2和H实现了ALE。(111)面的ALE温度窗口窄至20oC，而(100)面的ALE温度窗口宽至100oC。这种窄窗口的产生归因于改进的Ealy-Redeat机理，即H原子从Ge-甲基DON中减去甲基基团。利用SiH4气体实现了Si在Ge表面的单层吸附。通过在硅吸附的Ge表面上连续生长硅，实现了理想的单层数字生长。用俄歇电子能谱和SIMS分析了界面突变性，确认过渡层厚度为1 nm，与原子突变的Si-SiO_2系统的过渡层厚度相同，说明Si/Ge异质界面是原子突变的。通过15次GeCl4和H的曝光，实现了Ge在Si(100)表面的单层吸附，利用Ge-ALEs实现了Ge在该表面的数字沉积。结合这四种元素技术，我们制备了Si7Ge3人造晶体，证实了Si和Ge的层状结构。

Growth characteristics have been investigated in detail for atomic-layr epitaxy (ALE) of Si on the (111) surface by using SiH2Cl2 and atomic H.Gas-phase-generation of SiHCl radials by collision plays a very important role for an ideal one monolayr per cycle growth rate, and there are proper gas pressure and residence time for dense generation of SiHCl radials. For (100) surface, atomic H can etch the SiCl molecule chemisorbed on the surface, and this hydrogen pressure should be kept low. Based on these results, a wide ALE temperature window has been achieved for both (100) and (111) surfaces.Ge-ALE has been achieved by using GeH2(CH3)2 and H for the (100) and (111) surfaces. The ALE temperature window for the (111) surface was as narrow as 20oC while it was as wide as 100oC for the (100) surface. Origin of this narrow window was attributed to the Modified Ealy-Redeal mechanism for the atomic H induced subtraction of methyl groups from the Ge-methyl dond.Monolayr adsorption of Si has been achieved on the Ge surface by using SiH4 gas. Digital growth with an ideal one-monolayr step was achieved by successive Si-ALE on the Ge surfase adsorbed by Si. Interface abruptness has been evaluated by AES and SIMS and it was confirmed that the transition layr was as thin as 1nm , Since this value was the same to the transition layr thickness of atomically abrupt Si-SiO2 system , we have concluded that the Si/Ge hetero interface was atomically abrupt.Mono-layr adsorption of Ge on Si(100) surface was achieved by 15 cycles exposure of GeCl4 and H.Digital deposition of Ge was achieved on this surface by using Ge-ALE.Combining these four elemental techniques, we have fabricated Si7Ge3 manmade crystals and confirmed the layred structure of Si and Ge.