Total photoyield experiments on hydrogen terminated n-type diamond

Total photoyield spectroscopy (TPYS) is applied to characterize the surface electronic properties of n-type chemical-vapour-deposited (CVD) (111) homoepitaxial diamond with hydrogen termination (H-termination). To discuss the negative electron affinity of n-type diamond surfaces in a general way, TPYS is also applied on p-type diamond such as a high-pressure and high-temperature synthetic (HPHT) IIb (001) and a homoepitaxially grown CVD (111) film with H-termination. In case of IIb sample, a temperature dependent experiment was also applied. The onset of electron emission at 4.4 eV on p-, and n-type diamond indicates that Fermi levels do not affect the sub-band spectra. The sub-band spectra in the energy regime 4.5–5.2 eV shows nearly no temperature dependence between RT and 300 °C, than the TPY spectra above 5.2 and below 4.4 eV. Obviously, direct excitation of valence-band electrons into the vacuum takes place in the close vicinity of the surface with temperature independent optical cross sections.It is interesting to note that the expected rise of photoyield due to NEA in the regime hν > 5.47 eV is missing in n-type diamond. We attribute this to a surface space charge region arising from ionized phosphorous atoms.