Control of size and shape of ncSi in aSiN_x/aSi:H multilayers by laser induced constrained crystallization

Size-controlled nanocrystalline silicon (ncSi) has been prepared from aSiN_x/aSi:H multilayers by pulsed laser induced crystallization. Transmission electron microscopy (TEM) analyses show that the growth of ncSi is constrained by the aSiN_x/aSi:H interface, and the size of ncSi is controlled by the laser energy density and the aSi sublayer thickness when the aSi sublayer thickness is less than 10 nm. On the basis of the experimental results, we discuss the transitional process from the spherical shape to the cylindrical shape in the growth model of ncSi crystallization. The constrained effect for the crystal growth increases with a decrease of the aSi sublayer thickness. The critical thickness of the aSi sublayer for constrained crystallization can be determined by the present model. Moreover, the increase of the crystallization temperature in the ultra-thin aSi sublayer can be explained.