Field emission microscopy study of cesium adsorbed on ZrB2, and TiB2

Field emission microscopy was used to investigate the thermal desorption of cesium from ZrB2 and TiB2 surfaces. Described is a method of extracting th e work function and effective emitting area from the Fowler-Nordheim data w ith minimum assumptions. Work functions were measured after heating at succ essively higher desorption temperatures, assuming a value of 2.2 eV for the cesium saturated surface. The minimum value of the work function for the c esium coated ZrB2 surface was 2.04+/-0.1 eV, while that of the TiB2 surface was 1.74+/-0.05 eV. Average work functions of the thermally cleaned ZrB2 a nd TiB2 surfaces were found to be 3.78 eV and 5.44 eV, respectively. Activa tion energies for thermal desorption of cesium from ZrB2 and TiB2 were foun d to be 1.1+/-0.1 and 0.71+/-0.2 eV, respectively. (C) 1999 American Vacuum Society. [S0734-211X(99)08902-7].