Extremely high quantum photoyield from cesiated polycrystalline diamond films

An extremely high quantum photoyield, as high as 70% at the photon energy o f 10 eV, was observed from cesiated polycrystalline diamond films. The thre shold photon energy of 5.5 eV or less was observed. The results suggest tha t the cesiated polycrystalline diamond surface has a true negative electron affinity. In contrast, a quantum photoyield of 17% at the photon energy of 10 eV was observed for a hydrogenated polycrystalline diamond film. The th reshold photon energy of 5.5 eV or less was also observed, as in the cesiat ed one. It seems that the hydrogenated polycrystalline diamond surface has an effective negative electron affinity.