Thermal conductivity of high purity synthetic single crystal diamonds

Thermal conductivity of three high purity synthetic single crystalline diamonds has been measured with high accuracy at temperatures from 6 to 410 K. The crystals grown by chemical vapor deposition and by high-pressure high-temperature technique demonstrate almost identical temperature dependencies $\kappa \left(T\right)$ and high values of thermal conductivity, up to 24 $\mathrm{W}{\mathrm{cm}}^{-1}{\mathrm{K}}^{-1}$ at room temperature. At conductivity maximum near 63 K, the magnitude of thermal conductivity reaches 285 $\mathrm{W}{\mathrm{cm}}^{-1}{\mathrm{K}}^{-1}$, the highest value ever measured for diamonds with the natural carbon isotope composition. Experimental data were fitted with the classical Callaway model for the lattice thermal conductivity. A set of expressions for the anharmonic phonon scattering processes (normal and umklapp) has been proposed which gives an excellent fit to the experimental $\kappa \left(T\right)$ data over almost the whole temperature range explored. The model provides the strong isotope effect, nearly 45%, and the high thermal conductivity ($>24$ $\mathrm{W}{\mathrm{cm}}^{-1}{\mathrm{K}}^{-1}$) for the defect-free diamond with the natural isotopic abundance at room temperature.

Figure 1

Thermal conductivity of type IIa single crystalline diamonds versus temperature. This work: circles and triangles. Slack73: experimental data [3] for two HPHT diamonds with cross sections $3.4\times 3.4{\mathrm{mm}}^2$ (open squares) and $1.0\times 1.0{\mathrm{mm}}^2$ (open diamonds), and with $\left[\text{N}\right]=0.1$ and 50 ppm, respectively. BHM75 (stars): measured data [4] for natural diamond with cross section about $1\times 1{\mathrm{mm}}^2$ and length $\approx 6$ mm. The error bars are larger than the symbols size only at temperatures below 9 K.

Figure 2

The temperature dependence of thermal conductivity of diamonds at high temperatures. Symbol designation is as in Fig. 1.

Figure 3

The temperature dependence of thermal conductivity of single crystalline diamonds: experimental (symbols) and theoretical (lines) data. The dashed lines are calculation results of the Wei's model for their experiment [13] with diamonds with natural ${}^{\text{nat}}\mathrm{C}$ and enriched ${}^{12}\mathrm{C}$(99.9%) isotopic compositions; the dotted line is the Wei's model result for our sample NE6; solid lines are the fits to experimental data with our model.

Figure 4

Contributions of Debye and Ziman terms ${\kappa }_1\left(T\right)$ and ${\kappa }_2\left(T\right)$ to the thermal conductivity of diamond. Triangles are measured data for the sample NE6, solid red and dashed red lines represent the best fit to experimental data and the calculations for defect-free sample, respectively. Two close pairs lines (black) depict ${\kappa }_1\left(T\right)$ and ${\kappa }_2\left(T\right)$, respectively, for the best fit (solid) and for the defect-free (dashed) cases.