Dynamical growth processes of group IV semiconducting films on the polar surfaces of compound semiconductors as assessed by RHEED rocking curve

近年来，IV族半导体（111）面的生长模式引起了人们极大的兴趣。然而，关于III-V族化合物半导体的{111}极性表面上的生长方式的报道很少。本工作的目的是（i）测定InSb {111} A，B-（2*2）原子配位的表面法向分量，（ii）用反射高能电子衍射（RHEED）研究α-Sn膜在这些表面上的动态生长过程。（1）通过基于动态衍射理论的RHEED摇摆曲线的定量分析，确定了InSb {111} A，B-（2*2）表面的表面法向原子坐标。InSb（111）A ~（2*2）的表面In原子表现出较大的向内弛豫（-0.8）。另一方面，对InSb（111）B-（2*2）的分析表明Sb三聚体位于衬底Sb原子上方-2.8 °处，并且显著的弛豫发生在Sb三聚体下方的亚表面区域。(ii)用RHEED强度振荡技术研究了Sn在InSb {111} A，B上生长的表面。在整个薄膜厚度范围内，表面都在形成双层晶格。然而，两个系统的最外表面层的几何形状是完全不同的：在InSb（111）A上的生长表面平滑与晶格形成相同的周期，而在InSb（111）B上，低于和高于6 ML的Sn，光滑表面分别出现单层和双层的每个周期。表面几何形状的单层周期变化归因于生长表面上的Sb偏析。

Recently, growth mode of the (111) surface of group-IV semiconductors has generated great interest. However, little work has been reported on the growth fashion on the {111} polar surfaces of III-V compound semiconductors. The purpose of this work is (i) to determine the surface normal components of atomic coordinated of InSb {111} A,B- (2*2) and (ii) to study dynamical growth processes of alpha-Sn films on these surfaces by using reflection high-energy electron diffraction (RHEED). Main results are given as follows :(i) By the quantitative analysis of RHEED rocking curves based on the dynamical diffraction theory, we have determined the surface normal atomic coordinates of the InSb {111} A,B- (2*2) surfaces which have the In-vacancy bucking structure and the Sb-trimer structure, respectively. The surface In atoms of InSb (111) A- (2*2) exhibit a large inward relaxation (-0.8). The analysis of InSb (111) B- (2*2), on the other hand, has revealed that the Sb-trimer is located at a height of -2.8 above the substrate Sb atoms, and that the prominent relaxation occurs in the subsurface region beneath the Sb-trimer.(ii) Surfaces of Sn growing on InSb {111} A,B has been studied with use of the RHEED intensity oscillation technique. The surfaces proceed in the formation of a bilayred lattice in the whole range of film thickness. However, the geometry of the outermost surface layr is quite different in both systems : The growing surface on the InSb (111) A smoothens with the same period as the lattice formation, whereas on InSb (111) B,below and above 6 ML of Sn, smooth surfaces emerge every period of monolayr and bilayr, respectively. The monolayr-period change in surface geometry is attributed to Sb segregation on the growing surface.