Photoluminescence of silicon‐vacancy defects in nanodiamonds of different chondrites

Abstract

Photoluminescence spectra show that silicon impurity is present in lattice of some nanodiamond grains (ND) of various chondrites as a silicon-vacancy (SiV) defect. The relative intensity of the SiV band in the diamond-rich separates depends on chemical composition of meteorites and on size of ND grains. The strongest signal is found for the size separates enriched in small grains; thus confirming our earlier conclusion that the SiV defects preferentially reside in the smallest (≤ 2 nm) grains. The difference in relative intensities of the SiV luminescence in the diamond-rich separates of individual meteorites are due to variable conditions of thermal metamorphism of their parent bodies and/or uneven sampling of nanodiamonds populations. Annealing of separates in air eliminates surface sp 2 -carbon, consequently, the SiV luminescence is enhanced. Strong and well-defined luminescence and absorption of the SiV defect is a promising feature to locate cold (< 250 °C) nanodiamonds in space.

Ion implantation in nanodiamonds: size effect and energy dependence

“…Our results indicate that heating effects due to ion impacts may give rise to qualitatively similar heating effects. Size dependence of the Si-V luminescence intensity of meteoritic NDs may be explained by such processes, as substantial heating of small NDs by Si ion implantation can promote the formation of an optically-active SiV defect [27]. In contrast to the UV-related heating which is primarily determined by the absorption coefficient and grain size, the effect of ions demonstrates remarkable energy dependence with the existence of a "sweet spot".…”

Effects of sonochemical treatment on meteoritic nanodiamonds

“…For example, the silicon impurity which clearly resides as a point defect in the ND lattice (see Shiryaev et al. and references therein) is, apparently, not sensitive to the treatment. At the same time, the nitrogen impurity, which largely resides in extended defects (Shiryaev et al.…”

“…This could be due to weakness of the SiV feature in the Orgueil nanodiamonds (see Shiryaev et al. and references therein) and/or due to low volatility of silicon compounds in comparison with noble gases and nitrogen. In addition, occurrence of the SiV defects preferentially in the smallest grains with an eventual difference of their surface chemistry from the larger ones (see below), may also contribute to the absence of a noticeable effect.…”

“…We cannot also exclude influence of the lattice imperfection of the nanodiamond grains on the magnitude of the sonochemical effects. For example, the silicon impurity which clearly resides as a point defect in the ND lattice (see Shiryaev et al [2015] and references therein) is, apparently, not sensitive to the treatment. At the same time, the nitrogen impurity, which largely resides in extended defects (Shiryaev et al 2011;Vlasov et al 2012), serves as a stress concentrator on the atomic level and is more readily altered.…”

“…Photoluminescence spectra of the OD7C and OD7 samples. The inset shows position of the sonicated sample on the diagram relating to the SiV intensity to meteorite class and ND grain sizes (adapted fromShiryaev et al 2015).…”