Photoluminescence of silicon-vacancy defects in nanodiamonds of different chondrites

TL;DR

This study investigates silicon-vacancy defects in nanodiamonds from various chondrites, revealing size-dependent luminescence properties and the influence of thermal history, with implications for detecting nanodiamonds in space.

Contribution

It demonstrates the presence of SiV defects in nanodiamonds from meteorites, showing size and composition dependence, and explores how annealing enhances luminescence for space detection.

Findings

SiV defects are more prominent in smaller nanodiamonds (<2 nm).

Luminescence intensity varies with meteorite composition and thermal history.

Annealing enhances SiV luminescence by removing surface sp2-carbon.

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 (less than 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 sp2-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 {\deg}C) nanodiamonds in space.