Electron emission mechanism of diamond characterised by combined XPS/UPS/FES

The origin of field-emitted electrons from various kind of diamond surface was investigated using the combined X-ray photoelectron spectroscopy (XPS) / ultraviolet photoelectron spectroscopy (UPS) / field emission spectroscopy (FES) system. As a result, the origin of field-emitted electrons from the hydrogen-terminated natural IIb diamond was found to be at the valence band maximum (VBM) and it was independent of the applied voltages, while the origin was defined to be 1.5 eV above the VBM for the nitrogen (N) lightly doped chemical vapor deposition (CVD) diamond. The result also indicated the shift in FES peak of lightly N-doped CVD diamond. This shift has been well explained by the fact that the FES Peak Energy - Emission Current characteristics can be best fitted to straight lines, in other words, the difference in the resistance of the diamond. In addition, an attempt was made to define the origin of field-induced electron emission for N heavily doped CVD diamond. The result strongly implies the possibility of conduction band minimum (CBM) as an origin of the emitted electrons through the NEA surface of diamond.