The Constrained Growth and Patterned Distribution of nc-Si from a-SiN_x/a-Si:H/a-SiN_x: Mechanism and Experiments

Abstract

We get size-controlled nanocrystalline silicon (nc-Si) from a-SiN_x/a-Si:H/a-SiN_x sandwich structures by thermal annealing. Transmission electron microscope analyses show that the mean size and the grain size distribution (GSD) of the nc-Si are controlled by the annealing conditions and the a-Si sublayer thickness. We build a theoretical model of constrained crystallization which can well interpret the phenomena of the growth halt of nc-Si and higher crystallization temperature for the thinner a-Si sublayer. The experimental results indicate that constrained crystallization method is promising to achieve uniform and high density nc-Si array either by thermal annealing or by laser annealing. Based on this investigation we employ the method of laser interference crystallization (LIC) to fabricate nanocrystal Si with the two-dimensional (2D) patterned distribution within 10 nm thick a-Si:H single layer. Si nano-crystallites are selectively located in the discal regions within the initial a-Si:H layer. The present method is promising to fabricate various patterned nc-Si arrays for device applications simply by changing the geometry of the mask.