Ion induced electron emission from chemically cleaned Si and Ge

A compelling yet basic question regarding ion induced electron emission (IIEE) from semiconductors has never been experimentally investigated: Can a larger number of electrons in the conduction band (closer in energy to the vacuum level) cause a larger IIEE yield (gamma)? The lack of fundamental measurements of gamma under varying surface and sub-surface circumstances has left this question open to speculation. Recent measurements related to IIEE from semiconductors have suggested that deep sub-surface conditions may in fact lead to significant variations in gamma. In this work, the IIEE yields of chemically cleaned silicon and germanium bombarded with a variety of noble gas ions have been measured at energies between 25 and 300 eV. Our measurements indicate that while the IIEE yields depend strongly on the ion being tested (due to the ion's potential energy) they do not increase with increasing conduction band electron density. These measurements are consistent with the assumption made in the most widely accepted theory for IIEE, and with our extension of this theory to incorporate conduction band electrons.