MECHANISM OF H-2 DESORPTION FROM H-TERMINATED SI(001) SURFACES

Semiempirical molecular orbital calculations were performed to investi gate the mechanism of H-2 desorption from dihydride species on Si(001) surfaces. The lowest energy pathways were calculated with respect to three different mechanisms which have been proposed previously. We per formed additional calculations under the different H coverage conditio ns to examine the dependence of activation energy on the varieties of surrounding hydride species. The new transition state structure was ob tained by the calculation of the recombinative desorption of two H ato ms from adjacent Si dihydrides. We have found that the activation barr ier of the recombinative desorption mechanism was the lowest of all an d it was hardly influenced no matter what the surrounding hydride spec ies is.