Growth and characterization of strongly correlated suboxide thin films

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K05409
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics I
• Research Institution: Rikkyo University
• Principal Investigator: EDAMOTO Kazuyuki 立教大学, 理学部, 教授 (80185123)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: バナジウム酸化物 / 薄膜 / 電子状態 / 金属絶縁体転移 / 光電子分光 / 全反射高速陽電子回折

Outline of Final Research Achievements

The aim of this study is to synthesize a thin film of a VO crystal, whose physical properties have not been cleared because the crystal is hard to synthesize in an atmospheric condition, on an Ag(100) substrate that has a lattice well commensurate with VO(100). It was found that a V oxide film with a (1×1) periodicity with respect to Ag(100) can be formed by a reactive deposition method. The film was identified as the VO(100) film with a NaCl-type crystal structure from the analyses of photoemission spectroscopy (PES), X-ray absorption spectroscopy and total-reflection high-energy positron diffraction results. The electronic structure of the VO film was investigated by high-resolution PES, and it was found that the electronic structure of the film was metallic at temperatures higher than 4.86 K. The results indicates that the metal-insulator transition does not occur in the VO film, unlike the case for the other V oxides.

Free Research Field

表面化学

Academic Significance and Societal Importance of the Research Achievements

3d遷移金属酸化物は、構造が単純な強相関系として注目を集めてきた。これまでTiOは金属、MnO、FeO等は反強磁性絶縁体であることは判明していたが、その中間にあるVOの電子状態は不明であった。理論的にも、これが金属か絶縁体かは意見が別れていた。本研究ではVOは金属であることが明らかになり、これはVOをめぐる長年の論争に終止符を打つものである。また、バナジウム酸化物はそのMITの起源をめぐって膨大な研究が行われてきたが、VOのみはMITの有無すら不明であった。今回VOはMITを起こさないことが明らかとなった。以上は、物性物理学における長年のミッシング・リンクをつなぐ成果と言える。