Selective chemical etching of hexagonal boron nitride compared to cubic boron nitride

Abstract
A BN film containing comparable amounts of sp2 and sp3 phases was subjected to a gas-phase chemical etch in a hot-filament environment containing 1% CH4 in H2. After a partial etch, examination by FTIR shows that the sp2 was preferentially etched, leaving a larger sp3 fraction than in the unetched film. The possibility that preferential etching could be used to increase the purity of cBN films is discussed.