Etching Methods for Improving Surface Imperfections of Diamonds Used for X-ray Monochromators

In the last decade, diamond single crystals have become valuable monochromators for high-heat-load X-ray synchrotron beamlines. However, due to imperfections in the diamond, the rocking curves of diamond crystals are wider (e.g, 30%) than the theoretical values. Proper etching of the diamond can reduce the effects of imperfections. We explore four etching techniques using synthetic diamonds of type Ib and IIa. The diamond surfaces were variously treated by bombarding with ions, treating with a chemical solution, or using an atom-by-atom chemical machining process. Local variations of tilt and lattice parameter can be experimentally separated, and an improvement of the full width at half maximum (FWHM) of the rocking curve has been observed.