STEPWISE CHANGE IN GIBBS FREE-ENERGY CURVE OBSERVED IN SI(111) DAS DOMAIN GROWTH

The formation and the annihilation rates of stacking fault (SF) half-u nits were precisely determined from the high-temperature scanning tunn eling microscopy (STM) observation of dimer-adatom-stacking-fault (DAS ) domains gown on quenched Si(111) surface at 485 degrees C, as a func tion of the number of corner holes shared by a preexisting large domai n and a newly born single SF triangle. In contrast to the general nucl eation and growth with a single atom as a building unit, in the nuclea tion and growth of a n X n DAS domain with a single SF half-unit as a building unit, Gibbs free energy as a function of the number of SF hal f-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 was lower t han the annihilation rate due to the greater contribution of periphery strain to the increase in the Gibbs free energy than that of area inc rease. For the formation of the SF half-unit sharing two corner holes, the annihilation rate was negligibly small, suggesting that the addit ion of this single SF triangle increases the domain area keeping the p eriphery length constant, which results in Gibbs free energy reduction . (C) 1998 Elsevier Science B.V. All rights reserved.