Self-heating Schottky emission from a ballasted carbon nanotube array

A ballast resistor is utilized in a low density vertically aligned carbon nanotube array. Based on the nature of the ballast resistor, the uniformity of the emission improves remarkably. A highly stable field emission current is obtained under a constant voltage and a current density of 300 mA/cm2 is achieved. Joule heat generated by this field emission current increases the temperature of the CNT array significantly. The high temperature changes the emission to Schottky emission regime. The Schottky emission achieves 900 mA/cm2, which is three times the field emission current density. Simulation result shows the corresponding temperature is about 1700 K. A color change of the emission area is observed after the experiment. When compared to the conventional Schottky cathode, the emitter is self-heating and no extra heater is needed. This is the first report of a successful utilization of a ballast resistor in a CNT based emission array and the first observation of Schottky emission from a vertically aligned CNT array used as an electron emitter.