Effect of hole doping on the electronic structure of Nd1-xSrxTiO3.

Abstract

Photoelectron spectroscopy has been employed to follow the development of the electronic structure in ${\mathrm{Nd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{TiO}}_{3}$ as a function of x. Resonant effects at the Ti 3p threshold were used to highlight Ti 3d contributions in the valence bands. Particular attention is focused on Ti 3d intensity within \ensuremath{\sim}3 eV of the Fermi level (${\mathit{E}}_{\mathit{F}}$). The total intensity in this region is found to correlate linearly with composition, as expected. Changes in the shape of this spectral structure are discussed in terms of the one-electron spectral function. For x0.25 (insulating or semiconducting compositions), only incoherent intensity associated with the lower Hubbard band is present. Additional intensity, attributed to a coherent quasiparticle contribution, appears at the composition of the metal-insulator transition x\ensuremath{\sim}0.25. The relative intensities of these two components are determined as a function of x. Ti 3d intensity also occurs in the higher binding-energy region of the predominantly O 2p band due to Ti 3d--O 2p hybridization. Composition-dependent changes in this region are analyzed in order to determine changes in the Ti 3d--O 2p hybridization with composition and structure.