Boron and Nitrogen Isotope Effects on Hexagonal Boron Nitride Properties

Abstract The unique physical, mechanical, chemical, optical, and electronic properties of hexagonal boron nitride (hBN) make it a promising 2D material for electronic, optoelectronic, nanophotonic, and quantum devices. Here, the changes in hBN's properties induced by isotopic purification in both boron and nitrogen are reported. Previous studies on isotopically pure hBN have focused on purifying the boron isotope concentration in hBN from its natural concentration (≈20 at% ¹⁰B, 80 at% ¹¹B) while using naturally abundant nitrogen (99.6 at% ¹⁴N, 0.4 at% ¹⁵N), that is, almost pure ¹⁴N. In this study, the class of isotopically purified hBN crystals to ¹⁵N is extended. Crystals in the four configurations, namely h¹⁰B¹⁴N, h¹¹B¹⁴N, h¹⁰B¹⁵N, and h¹¹B¹⁵N, are grown by the metal flux method using boron and nitrogen single isotope (> 99%) enriched sources, with nickel plus chromium as the solvent. In‐depth Raman and photoluminescence spectroscopies demonstrate the high quality of the monoisotopic hBN crystals with vibrational and optical properties of the ¹⁵N‐purified crystals at the state‐of‐the‐art of currently available ¹⁴N‐purified hBN. The growth of high‐quality h¹⁰B¹⁴N, h¹¹B¹⁴N, h¹⁰B¹⁵N, and h¹¹B¹⁵N opens exciting perspectives for thermal conductivity control in heat management, as well as for advanced functionalities in quantum technologies.