Field emission from molybdenum carbide

The thermal stability and the resiliency of molybdenum carbide field-emissi on tips deposited at room temperature by electrophoresis have been studied. The field emission from Mo2C films deposited on Mo tips does not change af ter being heated to 800 degrees C while exposed to 360 L of air, although M oO2, MoO3, and possibly MoO, are present in the films. The field-emission t hresholds agree with photoelectric work functions determined from photoelec tron spectroscopy measurements of similarly grown flat samples. These films are found to exist in three distinct phases as a function of temperature a fter formation by room-temperature electrophoresis. From room temperature t o 500 degrees C, MoO3 is the dominant oxide, from 500 to 775 degrees C, MoC 2 is the dominant oxide, and above 825 degrees C both oxides have virtually disappeared. (C) 2000 American Institute of Physics. [S0003-6951(00)04218- 2].