0000000000749276
AUTHOR
Dongchen Qi
Cationic vacancies and anomalous spectral-weight transfer in Ti1−xTaxO2thin films studied via polarization-dependent near-edge x-ray absorption fine structure spectroscopy
We report the electronic structures of Ta-doped anatase TiO 2 thin films grown by pulsed laser deposition (PLD) with varying magnetization using a combination of first-principles calculations and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. The roles of Ta doping and Ti vacancies are clarified, and the observed room-temperature ferromagnetism is attributed to the localized magnetic moments at Ti vacancy sites ferromagnetically ordered by electron charge carriers. O K -edge spectra exhibit significant polarization dependence which is discussed and supported by first-principles calculations in relation to both the crystal symmetry and the formation of defects. In particula…
Revealing the Electronic Structure and Optical Properties of CuFeO2 as a p-Type Oxide Semiconductor
Delafossite CuFeO2 is a p-type oxide semiconductor with a band gap of ∼1.5 eV, which has attracted great interests for applications in solar energy harvesting and oxide electronics. However, there are still some discrepancies in the literature regarding its fundamental electronic structure and transport properties. In this paper, we use a synergistic combination of resonant photoemission spectroscopy and X-ray absorption spectroscopy to directly study the electronic structure of well-defined CuFeO2 epitaxial thin films. Our detailed study reveals that CuFeO2 has an indirect and d-d forbidden band gap of 1.5 eV. The top of the valence band (VB) of CuFeO2 mainly consists of occupied Fe 3d sta…