Growth of nano- and microcrystalline silicon thin films at low temperature by pulsed electron deposition

Abstract

Nanocrystalline silicon thin films were grown by using pulsed electron deposition onto substrates held at room temperature, and a substrate temperature up to 300°C can effectively improve the crystallinity of the deposits that they can be characterized as microcrystalline. Nanosized crystallites (<4nm) are formed in the ablation product, and upon their own kinetic energy and the heating effect from substrate, they become merged with neighboring particles in the amorphous matrix, resulting in Si films of excellent crystallinity that the full-width-at-half-maximum for the characteristic Raman peak at 520cm−1 measures as small as 4.17cm−1. The optical band-gap of such deposits varies from 2.0eV for the room temperature sample to 1.63eV for the sample grown at 300°C. With transmission electron microscopic images and selected area electron diffraction patterns the evolution of crystallinity for the deposits was revealed. These results demonstrate the feasibility of pulsed electron deposition for the controlled growth of nano- and microcrystalline silicon films at low temperature.