High-Resolution Measurements of Auger-Electron and Photoelectron Structure in the Secondary-Electron Energy Distributions of Aluminum, Nickel, and Copper

Measurements are reported of selected structure in the secondary-electron energy distributions of evaporated aluminum, nickel, and copper. The specimens were bombarded with 3-keV electrons and the secondary structure was measured with a resolution of 0.1 eV. For each metal, it was hoped to measure Auger transitions involving two relatively narrow inner-shell levels and the valence band in order to obtain information on the valence-band density of states. Attempts were made to observe the Al $K{L}_{2,3}M$ Auger-electron energy distribution expected at about 1470 eV. Structure was, however, observed with a high-energy edge of 1485.9 ± 0.5 eV and a breadth of 8-9 eV. This structure was interpreted as being due to photoemission of valence electrons by internally generated $K\alpha$ x rays and was similar to uv photoelectron energy distributions and to the calculated density of states. Inelastic scattering of the photoelectrons obscures the expected Al $K{L}_{2,3}M$ structure. Auger-electron peaks in the ranges 730-800 and 820-865 eV were measured in the secondary-electron energy spectra for nickel and copper, respectively. Structure was observed in the $L_3{M}_{2,3}{M}_{4,5}$ Auger transition (over a range of about 20 eV) that could be associated in part with the final atomic states and in part with over-all features of the $3d$-band density of states as determined by soft-x-ray-emission spectroscopy and x-ray photoelectron spectroscopy. It is believed that Auger-electron spectra can yield useful data on changes of electronic structure (e.g., by alloying or by compounding) but, in general, density-of-states data cannot be derived from the Auger spectra without detailed knowledge of the final states expected after the Auger transition of interest.