Homogeneous low-voltage field emission from nanographite films for cold cathode applications

Systematic field emission studies on PECVD grown nanocarbon films with vertically aligned thin graphite crystallites are reported. Field emission current maps of such nanographite cathodes with about 6 μm resolution revealed a number density of at least 7×104/cm² well-distributed nearly homogeneous emission sites at field levels of 1-2 V/μm. Local measurements reproducibly yielded FN-like current-voltage curves with a β-factor of about 1000 up to currents of 10 μA. SEM images of high-current processed spots revealed the onset of cathode destruction. Short-term current fluctuations were reduced to ±10 % after one hour. Luminescent screen images confirmed the FE homogeneity over the whole cathode. Therefore, a maximum current density of about 0.2 A/cm² can be achieved at voltages below 500 V. The application potential of these FE cathodes will be discussed.