Effective thermal and mechanical properties of polycrystalline diamond films

Hao Yu Cheng, Chi Yuan Yang, Li Chueh Yang, Kun Cheng Peng, Chih Ta Chia, Shiu Jen Liu, I. Nan Lin, Kung Hsuan Lin

研究成果: 雜誌貢獻文章

5 引文 斯高帕斯(Scopus)

摘要

Polycrystalline diamond films were demonstrated as good candidates for electron field emitters, and their mechanical/thermal properties should thus be considered for real devices. We utilized ultrafast optical techniques to investigate the phonon dynamics of several polycrystalline diamond films, prepared by microwave plasma enhanced chemical vapor deposition. The mechanical properties (longitudinal acoustic velocity) and thermal conductivities of diamond films were evaluated from the coherent and incoherent phonon dynamics, respectively. Ultrananocrystalline diamond films were grown using a CH4 (2%)/Ar plasma, while microcrystalline diamond films were grown using a CH4 (2%)/H2 plasma. The ultrananocrystalline diamond film (with a grain size of several nanometers) possesses low acoustic velocity (14.5 nm/ps) and low thermal conductivity (3.17 W/m K) compared with other kinds of diamond films. The acoustic velocity of diamond films increased abruptly to nearly the same as that of natural diamond and remained there when the rod-shaped diamond grains were induced due to the incorporation of H2 in the growth plasma (CH4/Ar). The thermal conductivities of the materials increased monotonously with increasing incorporation of H2 in the growth plasma (CH4/Ar). The thermal conductivity of 25.6 W/m K was attained for nanocrystalline diamond films containing spherical diamond grains (with a size of several tens of nanometers). Compared with single crystalline diamond, the low thermal conductivity of polycrystalline films results from phonon scattering at the interfaces of grains and amorphous carbon in the boundary phases.

原文英語
文章編號165105
期刊Journal of Applied Physics
123
發行號16
DOIs
出版狀態已發佈 - 2018 四月 28

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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  • 引用此

    Cheng, H. Y., Yang, C. Y., Yang, L. C., Peng, K. C., Chia, C. T., Liu, S. J., Lin, I. N., & Lin, K. H. (2018). Effective thermal and mechanical properties of polycrystalline diamond films. Journal of Applied Physics, 123(16), [165105]. https://doi.org/10.1063/1.5016919