The initial formation of the interface in the metal/compound-semiconductor system

了解金属/半导体系统中界面的形成过程和原子结构对于改进其工艺非常重要。因此，虽然这种界面已经被广泛研究了几十年，但与金属/化合物-半导体系统相关的工作还很少。在这项工作中，我们报告了扫描隧道显微镜(STM)对Sn/InSb(111)A-2x2系统界面形成的初始阶段的研究。到目前为止，该系统一直是RHEED研究和DV-Xα计算的主题。然而，关于“锡在InSb(111)A-2x2表面上吸附在哪里？”的问题。在超高真空中，通过在460ﾟ附近的窄范围内对样品进行热处理，可以重复地制备干净且定义良好的InSb(111)A-2x2衬底表面。对InSb(111)A-2x2表面的STM观察揭示了InSb(111)A-2x2表面的空位屈曲结构，这一结构已经由Bohr等人报道。例如，占据态的STM在高偏压下与In空位附近的第二层Sb的孤对相对应，在低偏压下与In最外层和Sb的第二层之间的成键轨道相对应。有时，观察到其边缘垂直于[112]或[112]方向的双向台阶。在电子计数模型的基础上，提出了一种新的阶梯结构模型。锡非周期性地吸附在InSb(111)A-2x2表面的以下三个位置上：In空位的顶部位置、第二层的Sb位置和最外层的In位置。在这些吸附位置中，In空位的顶部最容易被锡占据。

Understanding of the formation process and atomic structure of interfaces in the metal/semiconductor system is very important for improvements in its technology. Therefore, although such interfaces have been studied extensively for decades, little work associated with the metal/compound-semiconductor system has been carried out.In this work we report on the scanning tunneling microscopy (STM) study of the very initial stage of the interface formation in the Sn/InSb (111) A-2x2 system. So far this system has been the subject of RHEED investigation and DV-X alpha calculation. However, the question on "where is the Sn adsorbed on the InSb (111) A-2x2 surface? " has not been answered by direct methods such as STM.The clean and well-defined substrate surface of InSb (111) A-2x2 could be reproducibly prepared in UHV by annealing a sample in the narrow range near 460ﾟC.STM observations of the InSb (111) A-2x2 surface reveal the In-vacancy buckling structure which has been already reported by Bohr et al. For example, the STM for the occupied states manifests itself in the images corresponding to the lone-pair of Sb in the second layr near the In-vacancy at a high bias and to the bonding orbitals between the outermost layr of In and the second layr of Sb at a low bias. Occasionally, bilayr steps, the edges of which are perpendicular to eht [112] or [112] direction were observed. A novel model of these step structures is proposed on the basis of the electron counting model. The Sn is non-periodically adsorbed on the following three sites of the InSb (111) A-2x2 surface ; on-top sites of the In-vacancy, of the Sb in the second layr, and of the In in the outermost layr. Of these adsorption sites, the on-top of In-vacancy is most favorably occupied by Sn.