期刊
CRYSTALS
卷 11, 期 4, 页码 -出版社
MDPI
DOI: 10.3390/cryst11040322
关键词
polycrystal; cvd; diamond; thermal conductivity; isotope effect; phonon scattering; defect centers; dislocations
资金
- Russian Foundation for Basic Research [16-07-00979, 19-07-00229, 18-29-11023]
- National Research Center Kurchatov Institute
The study measured the thermal conductivity of polycrystalline diamond with different isotopic compositions, finding that the sample enriched with C-12 demonstrated higher thermal conductivity than the natural isotopic sample. A theoretical model was developed to explain the experimental data and estimate the impact of various scattering processes on thermal conductivity.
We measured the thermal conductivity kappa(T) of polycrystalline diamond with natural (natC) and isotopically enriched (C-12 content up to 99.96 at.%) compositions over a broad temperature T range, from 5 to 410 K. The high quality polycrystalline diamond wafers were produced by microwave plasma chemical vapor deposition in CH4-H-2 mixtures. The thermal conductivity of C-12 diamond along the wafer, as precisely determined using a steady-state longitudinal heat flow method, exceeds much that of the C-nat sample at T>60 K. The enriched sample demonstrates the value of kappa(298 K)=25.1 +/- 0.5 W cm(-1) K-1 that is higher than the ever reported conductivity of natural and synthetic single crystalline diamonds with natural isotopic composition. A phenomenological theoretical model based on the full version of Callaway theory of thermal conductivity is developed which provides a good approximation of the experimental data. The role of different resistive scattering processes, including due to minor isotope C-13 atoms, defects, and grain boundaries, is estimated from the data analysis. The model predicts about a 37% increase of thermal conductivity for impurity and dislocation free polycrystalline chemical vapor deposition (CVD)-diamond with the C-12-enriched isotopic composition at room temperature.
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