ハロゲンによるSi(100)-2×1表面のエッチング

抄録

We have studied the etching of Si(100)-2×1 by Cl and Br, using scanning tunneling microscopy to obtain morphological information that can be related to reaction and desorption pathways. Clean surfaces were exposed to molecular halogens at room temperature to produce well-defined chemisorption structures for coverages in the range 0.2-1.0 ML. Heating to 750-850 K induced etching by thermal desorption. Analysis of the halogen concentration before and after heating indicated that the rates of desorption for SiCl₂ or SiBr₂ were greatest for the intermediate coverage around 0.8 ML and were suppressed at the higher coverages. Hence, desorption is not simply proportional to the concentration of species that can form adsorbed precursors SiX₂(a). We conclude that it is directly coupled to the creation of monomer vacancies adjacent to the SiX₂(a) unit because this increases the lifetime of the excited state and increases the likelihood of its desorption. Increasing the surface concentration of halogens reduces the rate of vacancy formation. We show that these rates are also affected by a redimerization process in the high temperature Br-stabilized Si(100)-3×1 reconstruction that increases the likelihood of SiBr₂(a) formation and enhances its desorption.