Ultrananocrystalline Diamond Films as a High QE Photocathode

摘要

Quantum efficiency (QE) measurements of 150 nm nitrogen-incorporated ultrananocrystalline diamond films terminated with hydrogen, (N)UNCD:H, were carried out in the range between 250 and 440 nm. (N)UNCD:H demonstrated a QE as high as -0.1 % at 254 nm. Additionally, (N)UNCD:H was sensitive in visible light (405 to 440 nm) with a QE of ~5×10~(-6) % at 405 nm, which is comparable with QE range of poly crystalline copper photocathodes operated at 250-270 nm (with no MV/m gradients on the surface). Note, the (N)UNCD:H samples were transported ex situ in air. Achieved high QEs in near UV and visible ranges are thanks to introduction of electron states in the band gap close to the conduction band minimum via nitrogen incorporation and negative electron affinity introduced by hydrogen states on the (N)UNCD surface.