The constrained growth of uniform nc-Si grains from a-SiNx/a-Si:H/a-SiNx: mechanism and experiments

A mechanism of the growth of nanometer-sized crystalline silicon (nc-Si) in a-SiNx/a-Si:H/a-SiNx sandwich structures has been studied and the critical thickness of the a-Si sublayer for constrained crystallization has been presented based on the classical thermodynamic model. In order to examine the model, some experiments have been designed and carried out. A series of samples of sandwich structures with various a-Si sublayer thicknesses are annealed under different annealing conditions. The results show that the mean size and the grain size distribution (GSD) of nc-Si are controlled by a-Si sublayer thickness and thermal annealing conditions. We interpret the phenomena of the growth halt of nc-Si and higher crystallization temperature for the thinner a-Si sublayers. The experimental results coinciding with our model show that constrained crystallization method is promising to achieve uniform and high density nc-Si array which can be used in future nano-devices.