Photoemission spectra from conduction bands and core levels of sputter-deposited tantalum films

Abstract

Photoemission spectra of tantalum films, deposited by dc sputtering onto a room-temperature substrate, were obtained using a monochromatized aluminum x-ray source ($\mathrm{Al} K{\ensuremath{\alpha}}_{1,2}\ensuremath{-}1486.6$ eV) and a helium uv resonance lamp (HeI---21.2 eV, and HeII---40.8 eV). The x-ray photoemission spectra (XPS) were used to determine the density of electron states in the conduction band, the core-level binding energies, the spin-orbit splitting, and the chemical shift due to surface contamination. The much higher resolution ultraviolet photoemission spectra (UPS) were used to improve resolution of the conduction-band density of states near the Fermi level and to determine the work function. UPS data were also used to precisely calibrate the XPS energies. Comparison with similar experiments on tungsten indicate that the conduction bands are consistent with a rigid-band model.