Silicon (111) and (100) surfaces and their interactions with Cs,K, Na and Li; phase changes and kinetics of desorption studied by surface ionization

The rates of desorption of Cs, K, Na, and Li atoms from the (100) and (111) surfaces of silicon are followed by surface ionization. In the temperature range of the experiments, 800–1000 K, the surfaces are prepared in two forms. The first are metastable ones produced by cooling the crystals rapidly to temperatures below their surface phase transitions. These are a well-known one for the (111) face at 1120-40 K and one for the (100) face at 980 ± 20 K. The second forms are relatively stable surfaces to which the metastable ones convert spontaneously. On the metastable surfaces the desorption is first order and relatively rapid. Comparison with a model suggests that the atoms are highly mobile. On the more stable surfaces, where the desorption is mixed first and second order, a model fitting the results has the atoms also highly mobile but concentrated at steps or edges between terraces from which most of the desorption occurs. The sticking probability for the atoms is near unity on all the surfaces, and the smaller atoms, Na and Li, penetrate into the bulk to an appreciable extent.