Structure of silicon processed by severe plastic deformation

The structural features of nanocrystalline (NC) Si processed by severe plas tic deformation are considered. The results of studies by various technique s (transmission electron microscopy, X-ray diffraction, Raman scattering an d photoluminescence) are presented. The investigations show that the struct ure of NC materials is characterized by both a small grain size and a speci fic defect structure of grain boundaries associated with a high level of el astic strains and significant microdistortions of the crystal lattice. The Raman spectrum reveals a peak shift of 2.5 cm(-1) to lower frequencies, a p eak broadening up to 14.2 cm(-1), an asymmetry of the peaks and an addition al peak at frequencies from 480 to 500 cm(-1). A visible photoluminescence with a peak maximum at a wavelength of about 650 nm is observed. (C) 1999 E lsevier Science S.A. All rights reserved.