Charge transfer in amorphous colored WO3 films observed by X-Ray photoelectron spectroscopy

X-ray photoemission spectra of W core levels and valence band in transparent and in situ uv-colored amorphous WO3 films show that coloration is related to the existence of occupied electronic W5+ states situated ∼2 eV above the valence band and localized on some tungsten sites. It is shown that x-ray photoelectron spectroscopy and optical data are understood if one considers the formation of a hydrogen-tungsten-bronze-like compound during uv irradiation. © 1976 The American Physical Society.