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 (≈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. Hexagonal boron nitride crystals with controlled concentrations of the boron (10B and 11B) and nitrogen (14N and 15N) isotopes are synthesized and their optical properties are measured, including their Raman spectra. This provides a method for tailoring hBN's optical and nuclear spin properties for specific applications.