Valence band structure of Cr doped VO2 thin films: A resonant photoelectron spectroscopy study

Abstract

We report the crystal, magnetic and electronic structures of Cr doped VO2 [i.e., V1−xCrxO2 (VCO), x = 0, 0.05 and 0.10] thin films studied using X-ray diffraction (XRD), Raman, Vibrating sample magnetometer (VSM) and various high energy spectroscopic techniques. These VCO films were deposited on an r-sapphire substrate by pulse laser deposition. XRD and Raman spectroscopy studies show that the films are preferentially grown along the a-axis and possess a single phase of monoclinic (M1) in VO2 and triclinic (T) in Cr doped VO2. Magnetic hysteresis was measured at room-temperature using VSM exhibits ferromagnetism in the VCO films. The electronic states of Cr ion in the VO2 matrix and their interaction with the cations, as revealed by the X-ray photoelectron spectroscopy rule out the possibilities of the Cr metal clusters in VCO films. While, the valence band spectra of this films indicate that they are mostly made up of O 2p and Cr 3d derived states in VCO samples, the resonant photoemission spectra provide the evidence for strong hybridization of Cr 3d states with V5+ defect states.