Luminescent diamond window of the sandwich type for X-ray visualization

A two-layered diamond plate is proposed as a transparent X-ray window visualizer. The plate consists of a thick substrate of a synthetic single-crystal high-pressure high-temperature (HPHT) diamond on which a thin \({\sim }10\, {\mu }m\) optically active layer of chemical vapor deposition (CVD) diamond doped with silicon and nitrogen, and is epitaxially grown. The photoluminescent properties of the diamond sandwich plate were studied under the influence of X-ray radiation before and after treatment of the plate with high-energy electrons and its thermal annealing. It was established that broadband luminescence with a maximum near 500 nm, associated with defects of the HPHT diamond substrate, dominates before electron treatment. The electron irradiation and subsequent annealing of the plate completely suppressed the broadband luminescence and significantly (by more than two orders of magnitude) increased emission intensity of nitrogen-vacancy centers (NV) in the CVD diamond layer. As a result, the luminescence of neutrally charged NV centers with a zero-phonon line at 575 nm became dominant. No luminescence of the silicon-vacancy (SiV) centers in the CVD diamond film was detected. The first results demonstrating the two-layered diamond plate as an X-ray visualizer are presented.