Final-state effect on x-ray photoelectron spectrum of nominally d(1) and n-doped d(0) transition-metal oxides

Article

关键词: ELECTRONIC-STRUCTURE;    PHOTOEMISSION;    SRTIO3;    SPECTROSCOPY;    BULK;    CE;   

DOI  :  10.1103/PhysRevB.92.035110

来源: SCIE

【 摘 要 】

We investigate the x-ray photoelectron spectroscopy (XPS) of nominally d(1) and n-doped d(0) transition-metal oxides including NbO2, SrVO3, and LaTiO3 (nominally d(1)), as well as n-doped SrTiO3 (nominally d(0)). In the case of single phase d(1) oxides, we find that the XPS spectra (specifically photoelectrons from Nb 3d, V 2p, Ti 2p core levels) all display at least two, and sometimes three distinct components, which can be consistently identified as d(0), d(1), and d(2) oxidation states (with decreasing order in binding energy). Electron doping increases the d(2) component but decreases the d(0) component, whereas hole doping reverses this trend; a single d(1) peak is never observed, and the d(0) peak is always present even in phase-pure samples. In the case of n-doped SrTiO3, the d(1) component appears as a weak shoulder with respect to the main d(0) peak. We argue that these multiple peaks should be understood as being due to the final-state effect and are intrinsic to the materials. Their presence does not necessarily imply the existence of spatially localized ions of different oxidation states nor of separate phases. A simple model is provided to illustrate this interpretation, and several experiments are discussed accordingly. The key parameter to determine the relative importance between the initial-state and final-state effects is also pointed out.

【 授权许可】

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