Temperature-dependent energy-level shifts of Spin Defects in hexagonal Boron Nitride

TL;DR

This study investigates how temperature affects the energy levels of spin defects in hexagonal boron nitride, revealing temperature-dependent shifts, stability at high temperatures, and potential for thermal sensing applications.

Contribution

It provides a comprehensive analysis of temperature effects on spin defect energy levels in hBN, including empirical modeling and a novel laser intensity detection scheme.

Findings

Zero-field splitting decreases with temperature following Varshni's law.

VB- defects remain stable up to 600 K.

Energy-level shifts are likely due to thermal expansion.

Abstract

Two-dimensional hexagonal boron nitride (hBN) has attracted large attentions as platforms for realizations for integrated nanophotonics and collective effort has been focused on the spin defect centers. Here, the temperature dependence of the resonance spectrum in the range of 5-600 K is investigated. The zero-field splitting (ZFS) parameter D is found to decrease monotonicly with increasing temperature and can be described by Varshni empirical equation perfectly, while E almost does not change. We systematically study the differences among different hBN nanopowders and provide an evidence of edge effects on ODMR of VB- defects. Considering the proportional relation between D and reciprocal of lattice volume, the thermal expansion might be the dominant reason for energy-level shifts. We also demonstrate that the VB- defects still exist stably at least at 600 K. Moreover, we propose a scheme for detecting laser intensity using the VB- defects in hBN nanopowders, which is based on the obvious dependence of its D value on laser intensity. Our results are helpful to gain insight into the spin properties of VB- and for the realizations of miniaturized, integrated thermal sensor.