The surface energy band diagrams and the electron affinity of hydrogen-terminated and oxygen-terminated highly phosphorous-doped single crystal diamond (111) surfaces have been studied by ultraviolet photoelectron spectroscopy, secondary electron spectroscopy, X-ray photoelectron spectroscopy and photoemission electron microspectroscopy. A hydrogen-terminated boron-doped diamond (001) surface was used as a reference of surface energy band diagram. The electron affinity of the H-terminated heavily P-doped diamond was determined to be 0.2 ± 0.15 eV, thus close to zero. The electron affinity of the O-terminated highly P-doped diamond was determined to be 0.0 ± 0.15 eV, thus can be negative. However, the surface energy bands for the two highly P-doped samples were found to have large amounts (3 eV) of upward bending toward surface.

The origin of field emission from a specific nano-diamond/carbon nanowall (ND/CNW) electron emitter, which has high and stable field emission characteristics, was examined by field emission spectromicroscopy and scanning electron microscopy. It was found that graphite sticks are present on the field emission sites of the films. Energy distribution curves of electrons fieldemitted from the specified sites have the same features as those field-emitted from a metallic substance (graphite). Thus, it was concluded that graphite sticks present on the ND/CNW film are responsible for the field emission.

The mechanism of field emission from a highly P-doped diamond (111) surface has been studied by field/photo emission electron micro-spectroscopy. It was found that field emission peaks were located at À3 to À6 eV with respect to the substrate Fermi level (E F ) and that photoemission peaks were located at À1 to þ2 eV with respect to the substrate E F . Comparing this with the knowledge of work function and electron affinity of the sample, the mechanism of field emission has been elucidated. Namely, field emitted electrons are tunnel-emitted from states around the surface E F and there is a large amount of resistive potential drop at the emission site.