2020 Fiscal Year Annual Research Report
Development of thermal transistor using transition metal oxide
| Project/Area Number |
20J14755
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| Research Institution | Hokkaido University |
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Principal Investigator |
KIM GOWOON 北海道大学, 情報科学研究科, 特別研究員(DC2)
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| Project Period (FY) |
2020-04-24 – 2022-03-31
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| Keywords | Thermal transistor / Transition metal oxide / Tungsten oxide / 1D atomic defect tunnel / Pulsed laser deposition |
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| Outline of Annual Research Achievements |
In this research, I introduced 1D atomic defect tunnels in tungsten oxide (WOx) film and clarified the physical properties of it.
Thermoelectric properties of 1D atomic defect tunnel stabilized tungsten oxide epitaxial film: Although introducing point defects or layers is known as an effective way to reduce the thermal conductivity, the coexistence of high electron conduction and low heat conduction is still challenging. I successfully introduced 1D atomic defect tunnels in WOx epitaxial film and, I found that WOx can be a good active material for a thermal transistor because it showed drastic differences in optical, electrical, and thermal transport properties between different x. [1] G. Kim* et al., ACS Appl. Electron. Mater. 2, 2507 (2020)
Large anisotropic electron transport in 1D atomic defect tunnel stabilized tungsten oxide epitaxial film: Materials having an anisotropic crystal structure often exhibit anisotropy in the electrical conductivity. Compared to complex transition-metal oxides (TMOs), simple TMOs rarely show large anisotropic electrical conductivity due to their simple crystal structure. I unexpectedly aligned 1D defect tunnels one-dimensionally and we discovered large anisotropic transport in 1D atomic defect stabilized WOx epitaxial film. I clarified the physical properties of nanostructure engineered WOx epitaxial film. [2] G. Kim* et al., ACS Appl. Mater. Interfaces 13, 6864 (2021)
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
The first year’s research proceeded more than expected. I published two SCI journal papers and I was awarded at two conferences. I introduced 1D atomic defect tunnels in tungsten oxide (WOx) film and clarified the physical properties of it.
[1] G. Kim* et al., ACS Appl. Electron. Mater. 2, 2507 - 2513 (2020).
Award: Excellent Presentation Award, 2020 Meeting of the Ceramics Society of Japan Tohoku-Hokkaido Branch, 2020
[2] G. Kim* et al., ACS Appl. Mater. Interfaces 13, 6864 - 6869 (2021).
Award: Poster Award, The 21st RIES-Hokudai International Symposium 間 [ma], 2020
Judging from these results, the first year’s research proceeded more than my expectation. Based on the results of the first-year research, I will realize a solid-state thermal transistor by using WOx as the active material.
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| Strategy for Future Research Activity |
Recently, I found that hexagonal (h-) WOx films can be grown on 111 YSZ substrate. The epitaxial h-WOx film is difficult to fabricate because of its structural instability. I successfully fabricated highly oriented epitaxial h-WO3 and it showed thermal transistor characteristics when the h-WOx film is electrochemically reduced/oxidized.
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