Boron and Nitrogen Isotope Effects on Hexagonal Boron Nitride Properties

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 (approximate to 20 at% B-10, 80 at% B-11) while using naturally abundant nitrogen (99.6 at% N-14, 0.4 at% N-15), that is, almost pure N-14. In this study, the class of isotopically purified hBN crystals to N-15 is extended. Crystals in the four configurations, namely h(10)B(14)N, h(11)B(14)N, h(10)B(15)N, and h(11)B(15)N, 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 N-15-purified crystals at the state-of-the-art of currently available N-14-purified hBN. The growth of high-quality h(10)B(14)N, h(11)B(14)N, h(10)B(15)N, and h(11)B(15)N opens exciting perspectives for thermal conductivity control in heat management, as well as for advanced functionalities in quantum technologies.