Low-cost growth of high-quality monoisotopic hexagonal boron nitride single crystals by using a boric acid precursor

Abstract

Monoisotopic boron enriched hexagonal boron nitride (hBN) has high thermal conductivity (¹⁰B or ¹¹B enriched), large phonon lifetime (¹⁰B or ¹¹B enriched) and strong neutron absorption cross-section (¹⁰B enriched) (overtakes the natural, non-isotopic-enriched hBN counterpart). This makes it highly desirable for the applications of neutron detectors, nanoscale electronics, and optical components. Herein, we studied on the synthesize of monoisotopic hBN single crystals (SCs) using isotope enriched boric acid based on the atmospheric-pressure high-temperature (APHT) method. X-ray diffraction measurements indicates monoisotopic hBN SCs are well crystallized. Detailed Raman measurements verifies the high crystal quality and uniformity. A dependent of the Raman peak position and the peak width on the isotope content is also observed, fitting well to theoretical calculations. In the cathodoluminescence spectra, the presence of longitudinal optical (LO) phonon-related emission at around 5.75 eV is also indicative of the high-quality crystal. Our results suggest a low-cost route for the synthesis of high-quality monoisotopic enriched hBN single crystal.