Hard and soft x-ray photoelectron spectroscopies (called HAXPES and SXPES) were performed at ∼8 and ∼1.25keV for the metal-insulator transitions (MIT) system VO2. From the sharp difference between HAXPES and SXPES in the O Is spectra, it was found that the clean surface of the metal VO 2 is covered with a less itinerant surface layer. Clear changes of the spectral shapes were observed in HAXPES on MIT for the V Is, 2p, 3s, 3p and O 1s core levels. The enhanced intensity of these core levels in the low-binding-energy (EB) region of the main peak in the metal phase is due to the non-local or long range screening effects. The V 3d valence band in the metal phase is composed of coherent and incoherent parts. The prominent peak near 0.9 eV in the insulator phase has an incoherent tail in the high-E B region and the peak and its lower EB components are understood to have a noticeable coherent component. It is experimentally confirmed that both electron correlation and band changes induced by lattice distortion are responsible for the spectral changes on MIT in VO2.
ASJC Scopus subject areas
- General Physics and Astronomy