Thermionic electron emission from nitrogen-doped homoepitaxial diamond

Nitrogen-doped homoepitaxial diamond films were synthesized for application as low-temperature thermionic electron emitters. Thermionic electron emission measurements were conducted where the emission current was recorded as a function of emitter temperature. At a temperature < 600 °C an emission current was detected which increased with temperature, and the emission current density was about 1.2 mA/cm2 at 740 °C. The electron emission was imaged with photoelectron emission microscopy (PEEM) and thermionic field-emission electron microscopy (T-FEEM). The image displayed uniform electron emission over the whole surface area. Thermionic emission and ultraviolet photoemission spectroscopy were employed to determine the temperature dependent electron emission energy distribution from the nitrogen-doped homoepitaxial diamond films. The photoemission spectra indicated an effective work function of 2.4 eV at 550 °C. These values indicate reduced band bending and establish the potential for efficient electron emission devices based on nitrogen-doped homoepitaxial diamond.