Temperature dependence of the electron and ion induced electron emission yield of Al, Cu and Ag

The electron emission yield was measured for impact of 3 keV electrons, 2 MeV H⁺, 4 MeV He²⁺ and 6 MeV O³⁺ ions on polycrystalline Al, Cu and Ag samples as a function of sample temperature in the temperature range of 25-450 °C. A significant influence of the surface morphology was found. For annealed samples, a linear decrease of the yield was observed for increasing temperature, which is quantitatively described by a temperature coefficient t. It is found that the values for t depend both on the sample material and on the type of projectile. The largest value was found for proton impact on Ag, when the yield decreased by 2% for 100 K temperature increase. In addition, the change of work function for sample temperatures of 25 and 450 °C were also measured. The temperature dependence of the yield on the type of projectile is qualitatively discussed. The influence of the temperature dependence of the work function on the yield is quantitatively estimated. It is found that this contributes significantly, but cannot completely explain the observed temperature dependence of the yield.