S-A STEP-GROWTH MECHANISM ON (001) SURFACES OF DIAMOND STRUCTURE CRYSTALS

S-A step growth mechanism of (0 0 1) surfaces of diamond structure cry stals was investigated by means of quantum chemical calculations. Adat oms migrating on dimer rows on the terrace become stationary at the do wn side of S-A steps, because of the high potential energy wall preven ting the adatoms running up the S-A steps. Thus, migrating adatoms hav e a higher probability of remaining at the down side of S-A steps than at any point of the terrace. The second adatom running down the S-A s tep or migrating on the same dimer row of the lower terrace has a high probability of meeting the first adatom remaining at the down side of the S-A step, and a new dimer is formed. It was concluded that the S- A step growth is a complex event; i.e., the formation of an isolated d imer at the S-A step is followed by S-B step growth starting from the newly produced dimer as the smallest nucleus. The S-B step growth prog ressing along the S-A step means one step propagation of the S-A step growth.