ATOM-PROBE AND FIELD-EMISSION ELECTRON SPECTROSCOPE STUDIES OF GE ON IR

The combination of an atom-probe (AP) and a field emission electron sp ectroscope (FEES) was employed to investigate the electronic structure of Ge layers on an Ir substrate. Germanium forms a thin film with a f airly uniform thickness, possibly owing to a small activation energy f or diffusion on Ir or the lattice matching between Ge and Ir. The FEES spectrum obtained from Ge layers thicker than 8-9 ML exhibits a semic onductive energy gap and a peak at 0.7 eV below the Fermi level as for Si on Mo. However, the minimum layer thickness to exhibit the semicon ductive spectrum profile is significantly thicker than that for Si on Mo. The observed difference could be attributed to the layer structure of the deposited Ge and to the narrower energy gap of Ge than that of Si.