Field Emission Properties of Diamond Particles: Electron Injection Into the Conduction Band by Tunneling at Thin Insulating Interface Layer

Mechanisms of the field emission from diamond particles (DP) with an insulating layer between the DP and the electrode was studied. The SiO2 thin layer was formed on metal substrate, and then the DPs were dispersed by the spin-coat technique. The chemical vapor deposited diamond films were formed on the DP to obtain well-defined DP surfaces. Energy positions of Fermi level (E(sub F)), valence band maximum (E(sub VBM)) and conduction band minimum (E(sub CBM)) of the DP surface were measured by ultraviolet photoemission spectroscopy (UPS). UPS spectra suggested that the surface of these specimens exhibited negative electron affinity (NEA). The field emission electron spectroscopy (FEES) spectra were measured using a stainless-steel grid electrode placed <1mm above the specimen with an extraction voltage (V(sub ex)). The FEES spectra exhibit peaks, which show energy shift (V(sub s)) toward the lower energy below E(sub F) with increasing V(sub ex). Vs is considered to be derived by the field enhancement at the insulating layer. Intensity of the field emission current (Ife) shows close relation with the V(sub s). The linearity of the Fowler-Nordheim (F-N) plot between I(sub fe) and V(sub s) was observed while the relationship between Ife and V(sub ex) show ambiguous characteristics. These results suggest that the field emission from the DP is mainly affected by field enhancement at insulating layer (between the DP and the electrode) rather than that at diamond surface (between the DP and vacuum). This work was supported by the FCT Project, which was consigned to JFCC by NEDO.