Influence of material properties on the performance of diamond photocathodes

Variations in photoyield at 186 and 252 nm have been measured from CVD diamond photocathode materials grown on silicon substrates, as the growth conditions and surface termination were changed. The photoyield increased rapidly for short growth times when the surface comprised a mixture of diamond and non-diamond phases in intimate contact, but this increase occurred at both wavelengths, so poor spectral selectivity resulted. Further growth caused the photoyield to decay as the diamond content of the film improved, before rising again at longer growth times, whence improved wavelength discrimination was also observed. Caesiation enhanced the photoyield observed compared to hydrogenated interfaces.