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학술지 Insulator-to-metal Transition in Ultrathin Rutile VO2/TiO2(001)
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D. J. Lahneman, 테티아나, D. B. Beringer, Haoyue Jiang, Chang-Yong Kim, 김현탁, M. M. Qazilbash
npj Quantum Materials, v.7, pp.1-8
Nanjing University
21HB1500, 휴대 단말용 급격한 전하방전 저전압 스위칭 소자 원천기술 개발, 노태문
An insulator-to-metal transition (IMT) is an emergent characteristic of quantum materials. When the IMT occurs in materials with interacting electronic and lattice degrees of freedom, it is often difficult to determine if the energy gap in the insulating state is formed by Mott electron?밻lectron correlation or by Peierls charge-density wave (CDW) ordering. To solve this problem, we investigate a representative material, vanadium dioxide (VO2), which exhibits both strong electron?밻lectron interaction and CDW ordering. For this research, VO2 films of different thicknesses on rutile (001) TiO2 substrates have been fabricated. X-ray diffraction (XRD) data show that ultrathin VO2 films with thickness below 7.5 nm undergo the IMT between rutile insulator below Tc and rutile metal above Tc, while an ultrathin VO2 film with a thickness of 8 nm experiences the structural phase transition from the monoclinic structure below Tc to the rutile structure above Tc. Infrared and optical measurements on a film of 7.2 nm thickness, below Tc, reveal the energy gap of 0.6 eV in the rutile insulator phase and the absence of the 2.5 eV bonding-antibonding CDW structure. Above Tc, a Drude feature in the optical conductivity reveals the IMT to a metallic phase. These results suggest that for VO2 films below a critical thickness of about 7.5 nm, the IMT occurs in the rutile structure of VO2 without the Peierls lattice distortion.
KSP 제안 키워드
5 nm, Charge-density wave, Critical thickness, Degrees of freedom(DOF), Different thicknesses, Energy gap, Optical conductivity, Rutile structure, X-ray diffraction (xrd), insulating state, insulator-to-metal transition
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