IMPROVED FIELD-EMISSION OF ELECTRONS FROM ION-IRRADIATED CARBON

Electron field emission from allotropes of carbon (graphite, diamondli ke carbon, and diamond) have been reported many times in the literatur e. This work explores the use of ion irradiation for improving electro n field emission from carbon fibers. Carbon fibers have been irradiate d with H, C, Ar, and Xe ions. Field emission characteristics have been measured as a function of ion dose. A reversible reduction in the req uired field for a fixed current level has been observed. The critical dose, D-c, defines the dose corresponding to the lowest field necessar y to emit a fixed current (5 mu A). The critical dose appears to corre late with the nuclear energy loss (collisions with atoms) of the ion i n the carbon fiber. Transmission electron microscopy and parallel elec tron energy loss spectroscopy analysis indicate an amorphous surface, and an increase in the sp(3) content of the fiber surface to 20%-30%. A corresponding decrease in the work function is expected and may acco unt for the improvement in electron emission. (C) 1997 American Instit ute of Physics.