Nickel-induced defects and their role in governing chlorine chemistry on the Si(100) surface

The effect on chlorine surface chemistry of surface defects (split-off dimers) induced by controlled nickel contamination of Si(100) surfaces has been studied. It is shown that the mechanism of chlorine surface etching changes significantly with the presence of a small amount of split-off dimer defects (<0.02 monolayer). A new defect-related low temperature SiCl2 desorption peak is observed at similar to 550 K, and the shape of the major SiCl2 desorption peak at similar to 950 K is changed. The presence of the low temperature SiCl2 desorption is attributed to the existence of SiCl2 surface species on the split-off dimer defects. The chlorine saturation coverage increases by up to similar to 10% in the studied range of defect densities. It is estimated that each split-off dimer defect contains 4.3+/-0.6 extra chlorine atoms compared to the ideal chlorine-saturated Si(100) surface. On non-defective Cl-dosed Si(100) surfaces, the electron stimulated desorption ion angular distribution (ESDIAD) images show only four off-normal Cl+ beams. With increasing defect density a new Cl+ beam develops in the normal [100] direction. This feature is associated with the Cl bonding on the split-off dimer defects, and is similar to that produced on a Si(100) surface containing point defects created in other ways. (C) 1997 Elsevier Science B.V.