Periodic Deviations in the Schottky Effect for Tantalum

Periodic deviations from the Schottky law in the thermionic emission from patchy surfaces of tantalum and thorium on tantalum have been measured for fields up to 3×${10}^5$ volts ${\mathrm{cm}}^{-1\mathrm{}}$, and at temperatures of 1200 and 1500°K. The work function of the clean tantalum as determined by Richardson plots was 4.03±0.04 ev, and was changed by approximately 1/2 volt by thorium deposition. A method was found for separating the periodic deviations from the patch effects.