Ultrahigh thermal conductivity in isotope-enriched cubic boron nitride.

Materials with high thermal conductivity (κ) are of technological importance and fundamental interest. We grew cubic boron nitride (cBN) crystals with controlled abundance of boron isotopes and measured κ over 1600 Wm-1 K-1 at room temperature in samples with enriched 10 B or 11 B. In comparison, we found the isotope enhancement of κ is considerably lower for boron phosphide and boron arsenide as the identical isotopic mass disorder becomes increasingly invisible to phonons. The ultrahigh κ in conjunction with its wide bandgap (6.2 eV) makes cBN a promising material for microelectronics thermal management, high-power electronics, and optoelectronics applications.