LOW-ENERGY ION-INDUCED ELECTRON-EMISSION FROM GAS-COVERED SURFACES

Measurements of ion-induced electron emission have been performed with helium and argon ions with energies between 300 and 900 eV on W, W wi th 10% Ti, Al, Al with 1% Cu, Al with 1% Si, Si, and Be. This article describes many of the important surface characteristics that influence the ion-induced electron emission. For low-energy ions, the substrate material was found to be less important as the velocity of the incide nt ion decreased. In the case of incident Ar+ the substrate material h ad a negligible effect on the emission for this energy range. The pres ence of an adsorbed layer enhanced emission in all cases. Heating the substrates resulted in oxidation of the surfaces and a subsequent incr ease in emission. The electron emission from aluminum samples with sma ller grain sizes was higher than samples of identical composition with larger grains. This effect is due to the greater number of adsorption sites resulting from the higher grain boundary area.