title: Controlling the Temperature and Speed of the Phase Transition of VO2 Microcrystals.
abstract: We investigated the control of two important parameters of vanadium dioxide (VO2) microcrystals, the phase transition temperature and speed, by varying microcrystal width. By using the reflectivity change between insulating and metallic phases, phase transition temperature is measured by optical microscopy. As the width of square cylinder-shaped microcrystals decreases from ∼70 to ∼1 μm, the phase transition temperature (67 °C for bulk) varied as much as 26.1 °C (19.7 °C) during heating (cooling). In addition, the propagation speed of phase boundary in the microcrystal, i.e., phase transition speed, is monitored at the onset of phase transition by using the high-speed resistance measurement. The phase transition speed increases from 4.6 × 10(2) to 1.7 × 10(4) μm/s as the width decreases from ∼50 to ∼2 μm. While the statistical description for a heterogeneous nucleation process explains the size dependence on phase transition temperature of VO2, the increase of effective thermal exchange process is responsible for the enhancement of phase transition speed of small VO2 microcrystals. Our findings not only enhance the understanding of VO2 intrinsic properties but also contribute to the development of innovative electronic devices.
authors.affiliation: Department of Physics, Yonsei University , Seoul 03722, Republic of Korea.
authors.forename: Joonseok
authors.initials: J
authors.lastname: Yoon
authors.affiliation: Department of Physics, Yonsei University , Seoul 03722, Republic of Korea.
authors.forename: Howon
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology , Hong Kong 999077, China.
authors.forename: Xian
authors.initials: X
authors.lastname: Chen
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Nobumichi
authors.initials: N
authors.lastname: Tamura
authors.forename: Bongjin Simon
authors.initials: BS
authors.lastname: Mun
authors.affiliation: Division of Applied Chemistry and Biotechnology, Hanbat National University , Daejeon 34158, Republic of Korea.|Advanced Nano Products , Sejong, 30077, Republic of Korea.
authors.forename: Changwoo
authors.initials: C
authors.lastname: Park
authors.affiliation: Department of Physics, Yonsei University , Seoul 03722, Republic of Korea.
authors.forename: Honglyoul
authors.initials: H
authors.lastname: Ju
keywords: high-speed resistance measurement; metal−insulator transition; microcrystal; phase transition speed; phase transition temperature; size effect; vanadium dioxide