Emergence and control of metal-insulator transition in rutile-type d1 electron system

2021 Fiscal Year Final Research Report

• Project/Area Number: 19H02620
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 30010:Crystal engineering-related
• Research Institution: National Institute of Advanced Industrial Science and Technology
• Principal Investigator: Shibuya Keisuke 国立研究開発法人産業技術総合研究所, エレクトロニクス・製造領域, 主任研究員 (00564949)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 金属絶縁体転移 / ルチル型遷移金属酸化物 / 二酸化バナジウム / 二酸化ニオブ

Outline of Final Research Achievements

Epitaxial thin films of rutile-type niobium dioxide (NbO2) were fabricated, and the electronic and optical properties of the films were examined. The NbO2 films exhibited a transition temperature of 1080 K, almost equivalent to that of single crystals. Three phonon modes corresponding to the Nb-Nb dimer were found in the low-temperature phase of NbO2 from the angular-dependent polarized Raman spectra. The electronic state of NbO2 was determined using a spectroscopic ellipsometer. It was found that the electronic band structure of NbO2 is very similar to that of vanadium dioxide (VO2). The both materials in the rutile-type d1 electron system have similar crystal structure, phonon modes, and electronic band structures in their low-temperature phase.

Free Research Field

機能性酸化物

Academic Significance and Societal Importance of the Research Achievements

二酸化バナジウムは室温付近340Kで金属絶縁体転移を示すため、メモリ・センサ・スイッチなどの電子・光デバイスへの応用が期待されている材料である。二酸化ニオブは、二酸化バナジウムよりも高温の1080Kで相転移を示すため、デバイス動作の安定化に資するものと期待されている。本研究で明らかとなった二酸化バナジウムと二酸化ニオブの特性の理解は、強相関電子系における相転移温度制御手法と物質設計技術の発展に貢献するものと考える。