期刊
ACS APPLIED MATERIALS & INTERFACES
卷 8, 期 3, 页码 2280-2286出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.5b11144
关键词
vanadium dioxide; metal-insulator transition; phase transition temperature; phase transition speed; size effect; microcrystal; high-speed resistance measurement
资金
- Basic Science Research Program through grants from the National Research Foundation of Korea (NRF) - Korean Government (MOE) [NRF-2012R1A1A2006948]
- GIST College's TBP Research Fund
- Yonsei University
- U.S. Department of Energy at Lawrence Berkeley National Laboratory [DE-AC02-05CH11231]
- [NRF-2015R1A5A1009962]
- [NRF-2015R1A2A2A01004084]
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 to similar to 1 mu m, the phase transition temperature (67 degrees C for bulk) varied as much as 26.1 degrees C (19.7 degrees 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 X 10(2) to 1.7 X 10(4) mu m/s as the width decreases from similar to 50 to similar to 2 mu m. 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.
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