Anisotropic Dielectric Breakdown Strength of Single Crystal Hexagonal Boron Nitride

TL;DR

This study measures the anisotropic dielectric breakdown strength of single crystal hexagonal boron nitride (h-BN), revealing directional differences and establishing a standard for quality assessment in electronic applications.

Contribution

It provides the first detailed measurement of anisotropic dielectric breakdown strength in h-BN, highlighting its directional dependence and implications for device reliability.

Findings

EBD+c = 3 MV/cm, EBD//c = 12 MV/cm

EBD//c for h-BN exceeds that of diamond

High-quality bulk h-BN sets a standard for CVD-grown layers

Abstract

Dielectric breakdown has historically been of great interest from the perspectives of fundamental physics and electrical reliability. However, to date, the anisotropy in the dielectric breakdown has not been discussed. Here, we report an anisotropic dielectric breakdown strength (EBD) for h-BN, which is used as an ideal substrate for two-dimensional (2D) material devices. Under a well-controlled relative humidity, EBD values in the directions both normal and parallel to the c axis (EBD+c & EBD//c) were measured to be 3 and 12 MV/cm, respectively. When the crystal structure is changed from sp3 of cubic-BN (c-BN) to sp2 of h-BN, EBD+c for h-BN becomes smaller than that for c-BN, while EBD//c for h-BN drastically increases. Therefore, h-BN can possess a relatively high EBD concentrated only in the direction parallel to the c axis by conceding a weak bonding direction in the highly anisotropic crystal structure. This explains why the EBD//c for h-BN is higher than that for diamond. Moreover, the presented EBD value obtained from the high quality bulk h-BN crystal can be regarded as the standard for qualifying the crystallinity of h-BN layers grown via chemical vapor deposition for future electronic applications.