Size-reduction of nanodiamonds via air oxidation

TL;DR

This study demonstrates a controlled air oxidation process to reduce nanodiamond size, affecting surface properties and nitrogen-vacancy centres, with implications for quantum applications.

Contribution

It provides quantitative data on size reduction rates and insights into nitrogen-vacancy centre stability during oxidation.

Findings

Average size reduction of 10.6 nm/h at 600°C

Removal of non-diamond carbon and organic material

Smallest stable NV centre observed at 8 nm

Abstract

Here we report the size reduction and effects on nitrogen-vacancy centres in nanodiamonds by air oxidation using a combined atomic force and confocal microscope. The average height reduction of individual crystals as measured by atomic force microscopy was 10.6 nm/h at 600 {\deg}C air oxidation at atmospheric pressure. The oxidation process modified the surface including removal of non-diamond carbon and organic material which also led to a decrease in background fluorescence. During the course of the nanodiamond size reduction, we observed the annihilation of nitrogen-vacancy centres which provided important insight into the formation of colour centres in small crystals. In these unirradiated samples, the smallest nanodiamond still hosting a stable nitrogen-vacancy centre observed was 8 nm.