Mechanism of solid phase crystallization of prepatterned nanoscale α-Si pillars

We have investigated the mechanism of crystallite nucleation and growth in prepatterned nanoscale α-Si pillars using transmission electron microscopy. The number of α-Si pillars that crystallize during annealing depends upon the pillar diameter and the density of nucleation sites at the α-Si /oxide interface, in the as-deposited film. These nucleation sites are presumed to be clusters of atoms exhibiting short-range order that are formed during the initial deposition of α-Si. Their density depends upon the specific deposition conditions. The density of nucleation sites is extracted from the measured pillar crystallization statistics using a Poisson distribution model. It is also observed that the orientation dependence of the crystal growth rate enhances the formation of a single grain inside each pillar. Significant reduction of defect density is achieved with high temperature annealing of sub- 100-nm pillars where the surface to bulk ratio is high. © 2007 American Institute of Physics.