Secondary Emission Studies on Ge and Na-Covered Ge

Abstract

The influence of work-function reduction and variation of the incident-beam angle on the secondary-electron yield and secondary-electron energy distribution from the (111) face of Ge have been studied. Reduction of the work function from 4.79 to 2.3 eV by deposition of Na increased the maximum yield from 1.2 to a value near 3.6, while the primary energy at which the maximum yield occurred increased from 700 to 2000 eV. The energy width of the slow secondary-electron energy distribution function decreased strongly both with increasing primary energy and decreasing work function. An investigation of the energy of secondary electrons involved in the yield variation with incident beam angle suggests that this variation in yield is a direct result of variation in the primary-electron backscattering coefficient. A bulk plasma loss of 16.7 eV is manifested in the total secondary-electron energy distribution function by a series of peaks lying at multiples of 16.7 eV below the elastic peak. In addition, a shoulder on the first 16.7 eV loss peak indicates the existence of an 11 eV surface plasma loss. An overlayer of Na does not seriously affect the bulk plasma loss spectrum, but shifts the 11-eV surface loss to about 13 eV and causes the appearance of a second 3.5-eV surface loss peak.