Isotopically Enhanced Thermal Conductivity in Few-Layer Hexagonal Boron Nitride: Implications for Thermal Management

Abstract

Hexagonal boron nitride (h-BN) has been highlighted as a promising low-dimensional material for thermal management of next-generation devices. The theory predicts that the thermal conductivity of h-BN increases above the bulk value as the thickness is reduced, but previous reports on few-layer (5–11 layer) h-BN have shown the opposite trend. We investigated the effect of isotopic engineering on the thermal properties of 11-layer h-BN single-crystal flakes. The thermal conductivities of natural (22% ¹⁰B, 78% ¹¹B) and monoisotopic (99% ¹⁰B) h-BN were determined by a modified optothermal Raman method in the range 300–400 K. At room temperature, values were as high as (630 + 90/–65) Wm^–1 K^–1 for monoisotopic h-¹⁰BN and (405 + 87/–65) Wm^–1 K^–1 for natural h-BN, corresponding to an isotopic enhancement of close to 60%. Both measured thermal conductivities either match or exceed previously reported values for bulk crystals, while the isotopic enhancement factor is approximately 35% higher for the isotopically enriched thin crystal compared to the equivalent bulk materials. The work presented here demonstrates isotopic engineering as a viable route to increased thermal conductivity in atomically thin h-BN, making it an outstanding platform material for thermal management in next-generation device applications.