Electron emissions from CVD diamond surfaces

摘要

Electron emission processes from single-crystalline CVD diamond surfaces by internally exciting electrons from the valence to conduction bands have been mainly investigated as well as their surface properties, using scanning tunneling microscopy, photoemission quantum efficiency measurements and electrical property measurements. In addition, Monte Carlo simulations have been employed to evaluate the impact ionization rates of carriers in diamond under high electric fields up to 1 × 10{sup}7 V/cm. The calculations demonstrate substantial impact ionization rates, which rapidly increase with increasing electric fields above 8 × 10{sup}5 V/cm. Highly efficient electron emissions with high emission current efficiencies of approximate unity have been attained from a MIS-type diamond layered structure that composed of heavily ion-implanted buried layer (M), undoped diamond (I) and hydrogenated p-type diamond (S) with an emission surface of a negative electron affinity. The high emission efficiencies obtained are discussed in relation to the field excitation of electrons from the valence band to the conduction band in the undoped diamond layer and the carrier transport to the diamond surface.