| Abstrakt: |
In this paper we describe the production of nanocrystals of silicon embedded in an amorphous silicon matrix. These were then modified by partially removing the amorphous phase. The band gap that defines the optoelectronic properties of silicon changes with crystallite size. Silicon nanocrystals exhibit a significant blue shift in the band gap with decreasing size. The contribution of the nanocrystals to the properties of the amorphous silicon matrix depends on their size, shape, orientation, distribution and volume fraction. These are properties that we are investigating and modifying. Such engineering of the optical and electronic properties could lead to new and improved optoelectronic devices. Thin films of silicon ranging from fully amorphous to polycrystalline have been deposited from pure silane by the Hot Wire method. The effect of deposition conditions: filament temperature, substrate temperature, silane flow rate, pressure, and time have been investigated. The conditions under which isolated nanocrystals embedded in an amorphous matrix form have been mapped. Selected films have been anisotropically etched to enhance the nanocrystalline features. The films have been investigated using UV–visible spectroscopy, Raman Spectroscopy, Fourier transform infra-red spectroscopy, transmission electron microscopy and selected area electron diffraction. [ABSTRACT FROM AUTHOR] |
