Raman and high-pressure photoluminescence studies on porous silicon

Abstract

We show that there is no correlation between the blue shift of the visible photoluminescence band and red shift of the Raman phonon line in porous silicon, in contrast to the recently reported results. We also report a drastic red shift of the photoluminescence peak position with pressure up to 6 GPa and show that this is much larger than that of the crystalline silicon. These observations cast doubt on the suggested mechanism of quantum size effects in porous silicon.

Size dependence of nanostructures: Impact of bond order deficiency

“…It seems to be unnecessary to involve the bond strain at the interface to Theoretical results: Si-1 was calculated using correlation length model [465]; Si-3 (dot) and Si-4 (rod) were calculated using the bulk dispersion relation of phonons [466]; Si-5 was calculated from the lattice-dynamic matrix [438]; Si-7 was calculated using phonon confinement model [467], and Si-8 (rod) and Si-9 (dot) were calculated using bond polarizability model [436]. Si-2 [468], Si-6 [469], Si-10 and Si-11 [453] Table 7 Vibration frequencies of isolated dimers of various nanosolids and their redshift upon bulk formation derived from simulating the size-dependent redshift of Raman optical modes, as shown in Fig.…”

Raman spectroscopy of optical phonon confinement in nanostructured materials

“…112 The Raman spectrum of p-Si consists of an asymmetrically broadened F 2g phonon line characteristic of nanocrystalline Si and an overlapping broad peak at 480 cm 1 associated with amorphous Si. 113,114 Fitting of the Raman spectrum to a confined phonon line shape has frequently been carried out to estimate the average particle size. 115 Confined phonons of p-Si have been found to be responsible for the photoluminescence arising from radiative recombination of carriers across the indirect transition 116 similar to that found in crystalline Si.…”

Electron and phonon confinement and surface phonon modes in CdSe–CdS core–shell nanocrystals

“…This has been proposed and explained by phonon confinement model [13]. Confinement of phonons for Si, Ge, BN, CdS, CdS x Se 1−x and many other nanocrystals have been reported in the literature [14,15,16,17,18,19].…”