Electron emission mechanism of hydrogenated natural type IIb diamond (111)

Clarification of the electron emission mechanism of diamond has been one challenging topic in the field of vacuum nanoelectronics. Electric field of less than 5 V/µm is enough to extract electrons from diamond, which is orders of magnitude lower than the value required for electron emission from metal emitter in general. There have been number of studies on the clarification of electron emission mechanism, however, unified model has not been proposed. The difficulty largely lies in determining the origin of emitted electrons. In this study, we succeeded in clarifying the electron emission mechanism of hydrogenated natural type IIb diamond (111) surface by using combined x-ray photoemission spectroscopy/ultraviolet photoemission spectroscopy/field emission spectroscopy (XPS/UPS/FES) system. Obtained spectra clearly defined the origin of emitted electrons at the valence band maximum (VBM). As applied voltage was increased, the number of emitted electrons increased, however, the origin remained at VBM independent of the applied voltage.