Quantitative analysis of the bond rearrangement process during solid phase epitaxy of amorphous silicon

Abstract

The atomic mechanism of solid phase epitaxy (SPE) of amorphous silicon (a-Si) on a single crystal silicon (c-Si) substrate has been investigated by quantitative analysis of the bond rearrangement process (BRP) at the a-Si/(100)c-Si interface during SPE. Nine steps of the BRP (which proceeds by the mechanism proposed by Spaepen and Turnbull (1979)) at the interface were examined. The BRP starts with breaking a bond and generating two dangling bonds at the interface. The network of a-Si near the (100) face of the c-Si substrate is then rearranged to form chair-type sixfold rings characteristic of the c-Si lattice. For a quantitative analysis of the BRP the equilibrium atomic coordinates are calculated at each step, using an energy relaxation program based on the Keating potential. Using the coordinates, the following results are obtained: the atomic displacements during the BRP are smaller than half the Si-Si bond length; and the BRP results in a decrease in the distortion energy, mainly by bond bending, the amount of which is in good agreement with the value estimated from the experimental heat of crystallization.