The Influence of Arsenic on Silicon Surfaces

The Influence of Arsenic on Silicon Surfaces Daniel Harvey Zavitz, PhD. Department of Chemistry University of Illinois at Chicago Chicago, Illinois (2011) Dissertation Chairperson: Dr. Michael Trenary Restructuring of the clean Si(112) surface due to annealing, and the role of the As precursor monolayer on clean Si(112) for the MBE growth of Si(112)/As/ZnTe/CdTe thin films were explored, employing Scanning Tunneling Microscopy (STM), X-ray Photoelectron Spectroscopy (XPS) and Low Energy Electron Diffraction (LEED). The arsenic monolayers were deposited on clean Si(112) surfaces under UHV, mimicking the first two steps in the MBE growth of single crystal Si(112)/As/ZnTe/CdTe thin films. The hypothesis for this research, presented in the MBE literature, predicts that the arsenic will be covalently bonded to the edge atoms of the bulk terminated Si(112) surface and that no surface faceting will occur. A STM survey was completed of Si(112) surfaces resulting from differing number, durations and temperature of annealing cycles. The structures observed on these surfaces include: 1) non-planar Si(111)-like facets running in the [1-10] direction, from above to below the Si(112) surface plane rotated 2o about the [11-1] direction; 2) a 2.05 nm periodicity in the [1-10] direction on the line where the (111) and (113) facet planes meet at the surface; 3) dual Si(111)-like hexagonal periodicities with a = 0.384 and a’ = 0.3905 nm that are matched to the surfaces; 4) a LEED image of a high temperature annealed Si(112) surface is presented with a proposed centered rectangular unit cell with a = 0.384 nm and b = 3.516 nm, and 5) long range ordering with a superlattice with hexagonal periodicity with a = 78.1 nm, for the high temperature annealed Si(112) surface. For the arsenic covered Si(112) surface the arsenic adlayer forms 2.0 nm rows in the [1-10] direction on the Si(112) surface and no faceting occurs. The atoms are not lattice matched to the bulk-terminated Si(112) surface but form a moiré pattern layer. The arsenic layer preserves the clean high temperature annealed Si(112) surface reconstructions as the surface is cooled to room temperature. Si(111)-like nanofacets are not observed for the room temperature Si(112)/As surface.