The electronic structure and chemical bonding in reactively magnetronsputtered ZrHx (x=0.15, 0.30, 1.16) thin films with oxygen content as low as0.2 at% are investigated by 4d valence band, shallow 4p core-level and 3dcore-level X-ray photoelectron spectroscopy. With increasing hydrogen content,we observe significant reduction of the 4d valence states close to the Fermilevel as a result of redistribution of intensity towards the H 1s - Zr 4dhybridization region at about 6 eV below the Fermi level. For low hydrogencontent (x=0.15, 0.30), the films consist of a superposition of hexagonalclosest packed metal (alpha-phase)and understoichiometric delta-ZrHx (CaF2-typestructure) phases, while for x=1.16, the film form single phase ZrHx thatlargely resembles that of stoichiometric delta-ZrH2 phase. We show that thecubic delta-ZrHx phase is metastable as thin film up to x=1.16 while for higherH-contents, the structure is predicted to be tetragonally distorted. For theinvestigated ZrH1.16 film, we find chemical shifts of 0.68 and 0.51 eV towardshigher binding energies for the Zr 4p3/2 and 3d5/2 peak positions,respectively. Compared to the Zr metal binding energies of 27.26 and 178.87 eV,this signifies a charge-transfer from Zr to H atoms. The change in theelectronic structure, spectral line shapes, and chemical shifts as function ofhydrogen content is discussed in relation to the charge-transfer from Zr to Hthat affects the conductivity by charge redistribution in the valence band.
展开▼
