XPS, UPS, and BIS study of pure and alloyed beta-UH3 films: Electronic structure, bonding, and magnetism

Abstract

Uranium hydride films with the beta-UH3 structure were successfully synthesized using reactive sputter deposition. Their composition can be modified, if cooling the substrate to 177 K, by incorporating Mo as alloying element, in analogy to bulk nanocrystalline (UH3)-Mo hydrides. The films were in detail studied by in situ XPS (4f, 5d, 6p, valence band), valence-band UPS, and BIS, revealing variations of electronic structure with respect to U metal, confronted with ab initio calculations. We could identify certain ionicity in the U-H bonding projected in a large shift of the 6p peaks to higher binding energies. The U-6d states partly shift above the Fermi level and partly hybridize with the H-1s states, which weakens the 5f-6d hybridization. Although large scale features of the band structure are consistently explained and 5f states remain at the Fermi level E-F, spectral features close to E-F are not well reproduced by DFT or DFT+U calculations. This situation suggests prominence of electron-electron correlations affecting spectral function in the conditions of intermediate 5f localization.