Study of electronic structure of VO2 through K- and L-edge resonance phenomena
The first order metal-insulator (M-I) transition observed in VO 2 at temperature of 341 K accompanies crystallographic transition from monoclinic (low temperature insulator) to tetragonal rutile (high temperature metal). As temperature decreases vanadiums dimerize and twist along c-axis (<001> direction) of high temperature rutile structure and induce structural transition to low temperature monoclinic.
Diffractive anomalous near edge structure (DANES) measurement is combination of X-ray diffraction and absorption spectroscopy, which can provide element-, phase, and crystallographic site-specific electronic structure. Vanadium K-edge DANES measurement from monoclinic phase above the M-I transition temperature confirmed existence of monoclinic metal phase (MMP). Implication of the observed MMP will be discussed in conjunction with carrier doping through surrounding metallic phase.
Vanadium 2p-3d resonance photoemissions from VO 2 thin film grown on n- and p-type silicon substrates have been used to study photo-carrier injection from silicon substrates at a low temperature. Photo-carrier injection modifies V3d - O 2p hybridization and surprisingly vanadium 2p 3/2 - 2p 1/2 intermixing as well. Possibility of intermixing of transition metal 2p state through hybridization with oxygen ligand will be discussed.
Host: Prof. Je-Geun Park