Bromine interaction with Si(100)-2 x 1: Chemisorption and initial stages of etching.

Abstract

The dissociative chemisorption of ${\mathrm{Br}}_{2}$ on Si(100)-2\ifmmode\times\else\texttimes\fi{}1 at 300 K and the initial stages of layer-by-layer etching at high temperature have been studied with scanning tunneling microscopy. The Si surface maintains the 2\ifmmode\times\else\texttimes\fi{}1 reconstruction upon Br exposure with low-yield adsorption-induced etching at room temperature. Annealing Br-covered surfaces at temperatures up to \ensuremath{\sim}800 K results in thermally activated etching, but the yield is low. Higher-yield etching of the steps and terraces takes place at \ensuremath{\sim}900 K. Healing of this etched surface begins at \ensuremath{\sim}1000 K, and there is complete Br desorption and restoration of the pre-etch morphology by \ensuremath{\sim}1100 K. Etching under continuous bombardment by ${\mathrm{Br}}_{2}$ at 900 K was studied by varying the halogen flux while keeping the fluence constant. Quantitative analyses of images obtained during the early stages of continuous etching showed differences in the morphologies that offered insight into etching mechanisms.