Dielectric breakdown of atmospheric-pressure grown hexagonal boron nitride single crystals

Abstract

High-quality hexagonal boron nitride (hBN) has emerged as a reliable dielectric material for two-dimensional (2D) electronic devices because of its atomic flatness, ultrahigh optical transparency, wide energy bandgap, and high dielectric breakdown field. Traditionally, the best-quality hBN is mostly synthesized under high pressure and high temperature (HPHT). Because the HPHT method requires complex apparatus and limits the size of hBN crystals, it is desirable to grow large-area and high-quality hBN single crystals by a simpler method such as the synthesis under atmospheric pressure and high temperature (APHT). However, the comprehensive characterizations of APHT grown single crystals, particularly the dielectric breakdown information required for electronic applications, are still lacking. Here, we fabricate more than 30 graphite/hBN/graphite devices to systematically characterize the dielectric breakdown behaviors of APHT grown hBN crystals, along with other hBN crystals grown by different methods or vendors for direct comparison. The field values of dielectric breakdown, defined by the onset of leakage current, monotonically increase with the decrease in hBN thickness. Below the thickness of 10 nm, the field value reaches above 8 MV/cm. The dielectric breakdown behavior is comparable to that grown by HPHT. Our statistic results, along with the characterizations of X-ray diffraction, Raman spectroscopy, atomic force microscopy, and optical second harmonic generation microscopy, show that the hBN crystal under APHT is an ideal substitute for designing and fabricating the best-quality 2D electronic devices.