Ion assisted crystal grain nucleation in a-Si: a low temperaturre route towards poly-Si formation

摘要

The processes of nucleating and growth of crystalline silcion grains in amorphous Si layers irradiated at temperatures between 450 and 530 deg C with different ion beams have been investigated in details using transmission electron microscopy. THe crystal growth kinetics exhibits a behavior sinilar to that observed during ion-assisted epitaxial crystallization, i.e. it increases by increasing the energy deposited into nuclear elastic collisions by the impinging ions, and weakjly decreases by increasing the irradiation dose rate. Viceversa, the nucleation rate decreases by increasing the energy deposition of the ion and strongly decreases byincreasing the dose rate. although the experiments span over a very wide range of process conditions, i.e. temperatures and ion beam parameters, we demsonstrate that a single description, based on the classical nucleation theory, and explain all the experimental results, allowing an accurate evaluation of all the kinetics parameters.