Preferential etching by flowing oxygen on the {100} surfaces of HPHT single-crystal diamond

Application of diamond is determined by its oxidation behaviour in some measure. Oxidation process of single-crystal diamond prepared under high pressure and high temperature (HPHT) has been studied by the thermal analysis, scanning electron microscope (SEM) and Raman spectrometer. The result of a simultaneous thermal analysis indicates that single-crystal diamond is oxidized at ~ 818°C at a heating rate of 5°C/min in the flowing oxygen. Based on the data of the thermal analysis at different heating rates, the activation energy is calculated by the Kissinger method. A weight loss rate increases with the rising heat treatment temperature from 600 to 800°C. After the oxidation at 800°C, etch pits emerge on the {100} surfaces of single-crystal diamond, while the {111} surfaces are smooth. Shapes of the etch pits on the {100} surfaces are inverted pyramidal hollows, with edges direction parallel to the direction.