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）表面的生长方式引起了人们极大的兴趣。然而，关于III-V型化合物半导体{111}极性表面生长方式的研究却很少。本工作的目的是：(1)测定InSb {111} A，B-(2*2)原子配位的表面法向组分；(2)利用反射高能电子衍射（RHEED）研究这些表面上α - sn薄膜的动态生长过程。主要结果如下：(1)基于动力学衍射理论，通过对RHEED摇摆曲线的定量分析，分别确定了具有空位屈曲结构的InSb {111} A、B-(2*2)表面和具有sb -三聚体结构的InSb {111} A、B-(2*2)表面的法向原子坐标。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-三聚体位于基底Sb原子上方-2.8的高度，并且在Sb-三聚体下方的亚表面区域发生了明显的弛豫。（ii）利用RHEED强度振荡技术研究了在InSb {111} A，B上生长的Sn表面。在整个薄膜厚度范围内，表面继续形成双层红晶格。然而，在两种体系中，最外层的几何结构是完全不同的：InSb (111) A的生长表面在晶格形成的同一时期变得光滑，而在InSb (111) B上，在6 ML Sn以下和6 ML以上，单层和双层的每个时期都出现光滑的表面。表面几何结构的单层周期变化归因于生长表面的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.