| Project/Area Number |
18K14078
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| Research Category |
Grant-in-Aid for Early-Career Scientists
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| Allocation Type | Multi-year Fund |
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| Review Section |
Basic Section 28020:Nanostructural physics-related
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| Research Institution | The University of Tokyo |
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Principal Investigator |
Anufriev Roman 東京大学, 生産技術研究所, 特任助教 (40815875)
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| Project Period (FY) |
2018-04-01 – 2020-03-31
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| Project Status |
Completed (Fiscal Year 2019)
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| Budget Amount *help |
¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000)
Fiscal Year 2019: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
Fiscal Year 2018: ¥2,340,000 (Direct Cost: ¥1,800,000、Indirect Cost: ¥540,000)
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| Keywords | phonons / thermal conductivity / thermal transport / nanowires / heat transport / phononics / heat conduction / thermoelectrics |
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| Outline of Final Research Achievements |
Unlike classical heat diffusion at the macroscale, nanoscale heat conduction in semiconductors can happen “ballistically”, i.e. without energy dissipation, because individual phonons can travel in straight lines for hundreds of nanometers without resistance. In the past few years, such ballistic heat conduction has been demonstrated in semiconductor nanowires and membranes. However, these demonstrations were rather indirect because they were based on measurements of overall thermal conductivity of the entire nanostructures.
Here, I measured the billistic heat conduction in nanowires more directly, comparing the heat dissipation through the nanowires of different shapes. These experiments yielded the length and temperature ranges of ballistic heat conduction silicon and enabled probing directionality of phonon transport in nanowires. I found that ballisticiy is strongest in shortest nanowires (400 nm) and at 4 K and gradually weakens at higher temperatures and longer nanowires.
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| Academic Significance and Societal Importance of the Research Achievements |
These results showed that silicon is can exhibit strong ballistic heat conduction only at low temperatures. Hence for real-world applications, such as heat dissipation in microelectronics, we should search for materials with longer phonon mean free path, such as SiC, BN, or BAs.
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