Center for Correlated Electron Systems

Seminar

Study of electronic structure of VO2 through K- and L-edge resonance phenomena

May 2, 2019l Hit 426
Date : May 16, 2019 14:00 ~ 15:30
Speaker : Dr. Chang-Yong Kim(Canadian Light Source)
Location : Bldg. 19, Rm. 210

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