Structural inhomogeneities in amorphous silicon layers observed by X-ray diffraction and Raman scattering

Structural inhomogeneities in amorphous silicon layers, prepared by r.f. ma gnetron sputtering, were detected and characterized by X-ray diffraction (X RD) and Raman scattering using samples either as-deposited or post-annealed at increasing temperatures. These inhomogeneities, which can be interprete d in terms of disordered domains around the voids and which depend on the a nnealing temperature, are identified through analysis of the first halo pro files of XRD patterns as well as of the low-frequency part of the Raman spe ctra. The first halo profile has been well reproduced by using two componen ts, one located at the low wave vector (left side) of the 111 line of c-Si (relaxed domains), the other one at the other side (disordered domains). Th e Raman spectra at low frequency (omega < 130 cm(-1)) show a deviation from Debye's law attributed to the coexistence of the extended acoustic-phonons (Debye's modes) with the quasi-localized modes in the structural inhomogen eities. (C) 1999 Elsevier Science Ltd. All rights reserved.