AVS 51st International Symposium
    Advanced Surface Engineering Tuesday Sessions
       Session SE-TuP

Paper SE-TuP2
Field Emission Enhancements from C-implanted Molybdenum

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: N.D. Theodore, College of William and Mary
Authors: N.D. Theodore, College of William and Mary
R.A. Outlaw, College of William and Mary
B.C. Holloway, College of William and Mary
D.M. Manos, College of William and Mary
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The vacuum microelectronic industry is developing large, compact field emitter arrays in high-brightness devices for flat panel displays and microwave tubes. Refractory carbides are materials of interest due to their reduced work function, stable emission, high current capability, and robustness. The purpose of this study was to better understand field emission enhancements observed in molybdenum carbide by comparing it to pure molybdenum. According to Fowler-Nordheim (FN) theory, field emission is determined by two parameters, the work function of a material and its surface roughness. Slope-intercept plots of the resulting FN data are then used to separate the effects of these variables. In this experiment, we deposited molybdenum onto both flat silicon samples and triangular silicon gratings that possessed a tip radius of approximately 10 nm. We then created molybdenum carbide by implanting carbon using plasma immersion ion implantation. Carbide formation was verified using XPS; both the C1s peak and the Mo3d peaks were shifted. Depth AES analysis determined that the carbon-implant extended ~45nm from the surface. The field emission results quantify the observed differences in work function and in emission current stability, and correlate these to variations in surface layer compositions and geometry. Moreover, flat samples did not exhibit repeatable electron emission. We conclude that in flat samples, field emission from surface defects dominates the measured emission current, and this mechanism is not explained by Fowler-Nordheim theory.