Amorphous silicon films and superlattices grown by molecular beam epitaxy: an optical analysis
; Lockwood, D. J.
; Baribeau, J.-M.
; Noël, M.
; Zwinkels, J. C.
; Fogal, B. J.
; Orapunt, F.
O'leary, S. K.
National Research Council Canada; NRC Institute for Microstructural Sciences; NRC Institute for National Measurement Standards
2002 MRS Spring Meeting, Symposium A, Amorphous and heterogeneous silicon-based films 2002, 2-5 April 2002, San Francisco, California, USA
We produce a novel form of amorphous silicon through ultra-high-vacuum molecular beam epitaxy. By depositing silicon atoms onto a fused quartz substrate at temperatures between 98 and 335°C, we obtain a silicon-based material that lacks the characteristic periodicity of crystalline silicon but nevertheless has 98% of its density. The impurity content of this material is studied through infrared and secondary ion mass spectroscopies. The primary impurity found is oxygen, with hydrogen and carbon atoms also being found at trace levels. The Raman spectra of the amorphous silicon films are measured and the results, as they relate to the presence of disorder, are interpreted. We also use this molecular beam epitaxy method to fabricate a number of amorphous silicon superlattices, comprised of thin layers of amorphous silicon separated with even thinner layers of SiO2. The optical properties of the films and superlattices are contrasted.