Nickel Induced Defects and their Role in Governing Chlorine Chemistry on theSi(100) Surface

摘要

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 channel is observed at approx. 550K and the kinetics of the major SiCl2 desorption channel at approx. 950K are 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 approx. 10% in the studied range of defect densities. It is estimated that each split-off dimer defect contains 4.3 plus or minus 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 Si(100) surface containing point defects created in other ways.