Unusual high thermal conductivity in boron arsenide bulk crystals

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Science  10 Aug 2018:
Vol. 361, Issue 6402, pp. 582-585
DOI: 10.1126/science.aat7932
  • Fig. 1 STEM characterizations of BAs.

    (A) Annular dark-field STEM image within one grain of BAs, looking down the [110] zone axis. (B) Low-magnification bright-field TEM image near the surface of the BAs crystal. Horizontal lines indicate the locations of mirror twin boundaries. (C) Annular dark-field STEM image showing the atomic structure of the mirror twin boundary from the region highlighted by the red box in (B). (D) Electron diffraction pattern of BAs within a single grain. (E) Electron diffraction pattern of BAs across the grain boundary, showing the presence of the mirror twin.

  • Fig. 2 TDTR and FDTR measurements.

    (A) Representative TDTR phase signals and best-fitted curves for a diamond crystal acquired from Element Six and a BAs crystal at different temperatures. The diamond sample has the natural carbon abundance (1.1% 13C) and a low level of boron [<0.05 parts per million (ppm)] and nitrogen (<1 ppm) impurities. The 300 K data are averaged over 200 and 140 runs at the same location for diamond and BAs, respectively. The data for BAs at higher temperatures are averages of about 10 runs and show slightly increased noise. (B) Representative FDTR signal phase as a function of the pump modulation frequency measured on a BAs crystal, diamond, sapphire, and fused silica. The phase lag between the probe and the pump increases with decreasing sample κ.

  • Fig. 3 Measured thermal conductivity of BAs in comparison with values from theoretical calculations and other crystals.

    Calculated κ versus temperature for BAs (black) and diamond (green) including only three-phonon scattering (dashed lines) and both three- and four-phonon scattering (solid lines); measured κ for diamond by TDTR (green diamonds); measured κ for BAs samples 1 (solid red symbols) and 2 (open red symbols) by TDTR; measured κ for sample 3 by FDTR (solid orange star, mean value), steady-state (SS; open blue squares), and lock-in Raman (open brown square) methods; and measured κ for sample 5 by the steady-state method (solid blue squares). Also shown are the fits to measured steady-state and TDTR κ for BAs (blue and red solid lines, respectively) and reported measured κ for GaN (21) and GaAs (22) (magenta and purple triangles, respectively). The error bars for the TDTR and FDTR data represent one standard deviation and were obtained via Monte Carlo simulations and derivative matrix-based analysis of uncertainty propagation, respectively (15). The error bars for the steady-state and lock-in Raman measurements were calculated by propagating random errors at 95% confidence and combining them with systematic errors (15).

  • Fig. 4 Steady-state comparative and lock-in Raman thermometry measurements.

    (A) Temperature modulation amplitudes (ΔT) measured by Raman thermometry at two locations on the Si bar and two locations on the BAs bar. The lines are linear fittings to the measurement data. The inset is a schematic diagram of the experimental setup for thermocouple (TC) and Raman measurements. (B) Amplitude spectrum of the measured Raman peak modulation for BAs at locations x = 3.38 mm (location 1) and 4.39 mm (location 2). The curve for x = 4.39 mm is shifted manually by +0.2 along the x axis so that it can be distinguished from the other curve. The inset shows the modulation of the Raman peak frequency of BAs at location x = 3.38 mm as a function of the cycle number during the first six cycles. (C) Temperature gradients (∇T) on the Si and BAs bars obtained from TC and Raman measurements. The ambient temperature was 308.9 K, and the heater power amplitude was 0.081 W. The TC measurement error bars include random uncertainties with 95% confidence and systematic uncertainty, and the Raman measurement error bars consist of random uncertainties from the signal-to-noise ratio and systematic error (15).

Supplementary Materials

  • Unusual high thermal conductivity in boron arsenide bulk crystals

    Fei Tian, Bai Song, Xi Chen, Navaneetha K. Ravichandran, Yinchuan Lv, Ke Chen, Sean Sullivan, Jaehyun Kim, Yuanyuan Zhou, Te-Huan Liu, Miguel Goni, Zhiwei Ding, Jingying Sun, Geethal Amila Gamage Udalamatta Gamage, Haoran Sun, Hamidreza Ziyaee, Shuyuan Huyan, Liangzi Deng, Jianshi Zhou, Aaron J. Schmidt, Shuo Chen, Ching-Wu Chu, Pinshane Y. Huang, David Broido, Li Shi, Gang Chen, Zhifeng Ren

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods
    • Figs. S1 to S33
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