Optically detected magnetic resonance of wafer-scale hexagonal boron nitride thin films

TL;DR

This study systematically investigates the optically detected magnetic resonance (ODMR) properties of wafer-scale hexagonal boron nitride (hBN) thin films grown by various methods, highlighting their potential for nanoscale magnetic sensing.

Contribution

It provides the first comprehensive comparison of ODMR characteristics across different hBN growth techniques and identifies optimal growth conditions for magnetic sensitivity enhancement.

Findings

All tested hBN films exhibit ODMR signals.

The thinnest 3nm film shows ODMR response.

Optimal growth temperature for magnetic sensitivity is 800-900°C.

Abstract

Hexagonal boron nitride (hBN) has recently been shown to host native defects exhibiting optically detected magnetic resonance (ODMR) with applications in nanoscale magnetic sensing and imaging. To advance these applications, deposition methods to create wafer-scale hBN films with controlled thicknesses are desirable, but a systematic study of the ODMR properties of the resultant films is lacking. Here we perform ODMR measurements of thin films (3-2000nm thick) grown via three different methods: metal-organic chemical vapour deposition (MOCVD), chemical vapour deposition (CVD), and molecular beam epitaxy (MBE). We find that they all exhibit an ODMR response, including the thinnest 3nm film, albeit with different characteristics. The best volume-normalised magnetic sensitivity obtained is 30uT/sqrt(Hz um^3). We study the effect of growth temperature on a series of MOCVD samples grown under otherwise fixed conditions and find 800-900C to be an optimum range for magnetic sensitivity, with a significant improvement (up to two orders of magnitude) from post-growth annealing. This work provides a useful baseline for the magnetic sensitivity of hBN thin films deposited via standard methods and informs the feasibility of future sensing applications.