An adatom migration process passing through the S-A step was studied i
n detail in the case of carbon atom migration on diamond (001) surface
s using the method of quantum theoretical calculations. It was conclud
ed on (001) surfaces of diamond structure crystals that the adatom mig
ration at the S-A step easily occurs from the upper terrace to the low
er one, but hardly takes place from the lower terrace to the upper one
.