Evaluating the defects in CVD diamonds: A statistical approach to spectroscopy

Abstract

Laboratory-grown diamonds produced by chemical vapor deposition (CVD) can have similar sizes and colors to natural diamonds, and their color can be enhanced by post-growth treatment. Despite considerable published research on CVD diamond growth, post-growth treatment remains difficult to detect in some CVD diamonds. To improve the detection of post-growth treatment, we apply multivariate statistics to photoluminescence (PL) emission spectra and surface fluorescence images from 11,606 gem-quality CVD diamonds within the D-Z color range. Unsupervised statistics indicate as-grown CVD diamonds commonly have 3H defects, with zero-phonon line (ZPL) at 503.5 nm, and relatively intense PL peaks at 467.6 nm. These features are absent or minor in diamonds treated under high-pressure, high-temperature (HPHT) conditions. HPHT-treated CVD diamonds tend to exhibit the H3 system (with ZPL at 503.2 nm) as well as larger 491.9 nm and 566.6 nm peak areas. A subset of CVD diamonds showing the H3 system could have experienced treatment at low-pressure high-temperature (LPHT) conditions (including inside the reactor during or after CVD growth).