A field emission diode based on aligned multiwall carbon nanotube (MWNT) arrays was conceptuallydemonstrated, and its thermal stability from room temperature to 300 °C was investigated. Ideal diode behaviorwas observed with negligible change of the device parameters with the variation of temperature. The turn-onvoltage and reverse leakage current of the MWNT diode can be readily controlled by simply varying thespacing between electrodes. Potential areas of application of the diode have been addressed.