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

Abstract

Photoemission spectra of tungsten films, deposited by sputtering onto a room-temperature substrate, were obtained using an aluminum x-ray source ($\mathrm{A}1 K{\ensuremath{\alpha}}_{1,2}\ensuremath{-}1486.6$ eV) and a helium uv resonance lamp (He I, 21.2 eV and He II, 40.8 eV). Film structure was determined by x-ray diffraction to consist mostly of bcc microcrystals. Spectra of electrons excited from the conduction band by x rays (XPS) and uv (UPS) are combined to deduce a high-resolution empirical density of electron states of the conduction band. The 10-eV Fermi energy agrees well with augmented-plane-wave calculations if relativistic effects and exchange are appropriately taken into account. The XPS data, when calibrated by the high-resolution UPS data with respect to the Fermi energy, provide accurate core-level binding energies. They also show electron energy losses due to 25-eV volume plasmon excitation.