Light emission from ion-bombarded Ge(1 0 0) surfaces under continuous germane and silane exposures

The intensities of the optical spectral lines emitted from a Ge(1 0 0) surface under Ar+ ion bombardment are studied as a function of the ion kinetic energy (1–5 keV) and the partial pressure (5 × 10−6–5 × 10−4 Torr) of either germane or silane. For germane exposures, the Ge (GeI, 265 nm and 304 nm), H Balmer beta (486 nm) and H Balmer gamma (434 nm) optical lines are observed. For silane, additional peaks due to excited neutral Si (SiI, 288 nm) and molecular SiH (A2Δ–X2Π, 414 nm) are visible. The ion kinetic energy dependence of the GeI photon yields (265 nm and 304 nm) is analyzed in terms of the electron exchange mechanism. The similarity between the measured de-excitation parameters for germane and silane pressure between 5 × 10−6 and 5 × 10−4 Torr implies that the de-excitation mechanism does not change significantly. For both germane and silane exposures, the intensities of excited neutral Ge, H beta and H gamma optical lines increase with either larger partial pressures or ion kinetic energy. A similar trend is found for neutral SiI and molecular SiH emission during silane exposures. In contrast, the intensity of the H Balmer alpha transition (656 nm) decreases with increasing incident ion kinetic energy at all measured partial pressures. Both trends are similar to that observed for either silane or germane exposed Si(1 0 0) surfaces under ion bombardment.