Hard X-ray photoelectron spectroscopy of LixNi1-xO epitaxial thin films with a high lithium content

L S R Kumara; Osami Sakata; Anli Yang; Ryosuke Yamauchi; Munetaka Taguchi; Akifumi Matsuda; Mamoru Yoshimoto

doi:10.1063/1.4891366

Hard X-ray photoelectron spectroscopy of LixNi1-xO epitaxial thin films with a high lithium content

J Chem Phys. 2014 Jul 28;141(4):044718. doi: 10.1063/1.4891366.

Authors

L S R Kumara¹, Osami Sakata¹, Anli Yang¹, Ryosuke Yamauchi², Munetaka Taguchi³, Akifumi Matsuda², Mamoru Yoshimoto²

Affiliations

¹ Synchrotron X-ray Station at SPring-8, National Institute for Materials Science (NIMS), 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan.
² Department of Innovative and Engineered Materials, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259-J3-16, Nagatsuta, Midori, Yokohama 226-8502, Japan.
³ Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), Ikoma, Nara 630-0192, Japan.

PMID: 25084948
DOI: 10.1063/1.4891366

Abstract

The core-level and valence-band electronic structures of LixNi1-xO epitaxial thin films with x = 0, 0.27, and 0.48 were studied by hard X-ray photoelectron spectroscopy. A double peak structure, consisting of a main peak and a shoulder peak, and a satellite structure were observed in the Ni 2p3/2 core-level spectra. The intensity ratio of the shoulder to main peak in this double peak structure increased with increasing lithium content in LixNi1-xO. This lithium doping dependence of the Ni 2p3/2 core-level spectra was investigated using an extended cluster model, which included the Zhang-Rice (ZR) doublet bound states arising from a competition between O 2p - Ni 3d hybridization and the Ni on-site Coulomb interaction. The results indicated that the change in the intensity ratio in the main peak is because of a reduction in the ZR doublet bound states from lithium substitutions. This strongly suggests that holes compensating Li doping in LixNi1-xO are of primarily ZR character.