The formation and the annihilation rates of stacking fault (SF) half units were precisely determined from the high-temperature STM observation of dimer-adatom-stacking fault (DAS) domains grown on quenched Si(111) surface at 485 degree C, as a function of the number of corner holes shared by a p reexisting large domain and the newly born single SF triangle. In contrast to the general nucleation and growth with a single atom as a building unit, in the nucleation and growth of an nxn DAS domain with a single SF half uni t as a building unit, Gibbs free energy as a function of the number of SF half units has discrete values. This feature is reflected in the behavior of a newly born SF half unit adjacent to a larger DAS domain. For the SF half units sharing one corner hole, the formation rate per one corner hole was lower than the annihilation rate due to the greater contribution of periphery strain to the increase in the Gibbs free energy than that of area increase. For the formation of the SF half unit sharing two corner holes, the annihilation rate was negligibly small, suggesting that addition of this single SF triangle increases the domain area keeping the periphery length constant, which results in Gibbs free energy reduction.
Figure. Successive STM images observed at around 485 degree C. The images of (b )-(i) were taken 9, 18, 52, 70, 88, 106, 112 and 150 seconds after (a), respectively. SF half units indicated by thick lines are the newly formed one after the previous image. An SF half unit sharing one corner hole annihilated in (i).