Quantitative trace hydrogen distributions in natural diamond using 3D-micro-ERDA microscopy

Abstract A 3-D quantitative microscopy for minor distributions of surface and near-surface bulk hydrogen in solid samples has been developed. The technique employs a 15 MeV Si 7+ microbeam and a two-dimensional position sensitive detector (2D PSD) with event reconstruction in an Elastic Recoil Detection Analysis (ERDA) geometry. Lateral resolutions of 10 μm and depth resolutions of 300 A at an MDL of 100 ppm are currently possible. The technique is quantitative due to the use of an internal implanted spot standard or by cross calibration to an H implanted reference sample using RBS as a normalisation transfer. Hydrogen content and configuration in diamond illuminates the genesis mechanism and environment. A hydrogen rich diamond exhibiting zoned cloud-like ensembles of micro-inclusions as well as smaller pockets of these inclusions has been interrogated for its near-surface-bulk hydrogen distribution. The sample has also been well characterised with optical microscopies and with bulk optical spectroscopies. A striking correlation between the hydrogen distribution and the optically visible inclusion have been obtained. This is the first direct evidence for aggregations of hydrogen associated with cloudy inclusions in natural hydrogen rich diamonds.