Electron Ejection from Single Crystals Due to 1- to 10-keV Noble-Gas Ion Bombardment

The secondary-electron ejection coefficient $\gamma$ has been measured for the (110), (100), and (111) planes of Cu, Al, Ag, Ni, and Mo bombarded by the singly charged noble-gas ions ${\mathrm{Ne}}^{+}$, ${\mathrm{Ar}}^{+}$, ${\mathrm{Kr}}^{+}$, and ${\mathrm{Xe}}^{+}$ in the energy range from 1 to 10 keV. Surfaces were kept clean to within a fraction of a monolayer contamination by the sputtering action of the incident ion beams. The ratios $\frac{{\gamma }_{\mathrm{hkl}}}{{\gamma }_{h^{\prime }{k}^{\prime }{l}^{\prime }}}$ are quite constant, which would tend to indicate a theoretical model based on simple geometrical considerations of the opacity of the single-crystal planes. However, the fact that the ratios are relatively insensitive to the ion-bombardment energy indicates that a model based upon the transparency of the target is not sufficient to explain the phenomenon. The dependence of $\gamma$ on the bombarding-ion mass is also explored.