Structure of silicon processed by severe plastic deformation

The structural features of nanocrystalline (NC) Si processed by severe plastic deformation are considered. The results of studies by various techniques (transmission electron microscopy, X-ray diffraction, Raman scattering and photoluminescence) are presented. The investigations show that the structure of NC materials is characterized by both a small grain size and a specific defect structure of grain boundaries associated with a high level of elastic strains and significant microdistortions of the crystal lattice. The Raman spectrum reveals a peak shift of 2.5 cm(-1) to lower frequencies, a peak broadening up to 14.2 cm(-1), an asymmetry of the peaks and an additional 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 Elsevier Science S.A. All rights reserved.