BROMINE INTERACTION WITH SI(100)-2X1 - CHEMISORPTION AND INITIAL-STAGES OF ETCHING

The dissociative chemisorption of Br2 on Si(100)-2 X 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 X 1 reconstruction upon Br exposure with low-yield adsorption-induced etching at room temperature. Annealing Br-covered surfaces at temperatures up to approximately 800 K results in thermally activated etching, but the yield is low. Higher-yield etching of the steps and terraces takes place at approximately 900 K. Healing of this etched surface begins at approximately 1000 K, and there is complete Br desorption and restoration of the pre-etch morphology by approximately 1100 K. Etching under continuous bombardment by Br2 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.