Temperature-Dependent Energy-Level Shifts of Spin Defects in Hexagonal Boron Nitride

• Published in: ACS photonics Vol. 8; no. 7; pp. 1889 - 1895
• Main Authors: Liu, Wei, Li, Zhi-Peng, Yang, Yuan-Ze, Yu, Shang, Meng, Yu, Wang, Zhao-An, Li, Ze-Cheng, Guo, Nai-Jie, Yan, Fei-Fei, Li, Qiang, Wang, Jun-Feng, Xu, Jin-Shi, Wang, Yi-Tao, Tang, Jian-Shun, Li, Chuan-Feng, Guo, Guang-Can
• Format: Journal Article
• Language: English
• Published: American Chemical Society 21.07.2021
• Subjects: electron spin resonance; van der Waals materials; Varshni empirical equation; thermal expansion; point defect; temperature sensor
• ISSN: 2330-4022; 2330-4022
• DOI: 10.1021/acsphotonics.1c00320

Two-dimensional hexagonal boron nitride (hBN) has attracted much attention as a platform for realizing integrated nanophotonics, and a collective effort has been focused on spin defect centers. Here, the temperature dependence of the optically detected magnetic resonance (ODMR) spectrum of negatively charged boron vacancy (VB –) ensembles in the range of 5–600 K is investigated. The microwave transition energy is found to decrease monotonically with increasing temperature and can be described by the Varshni empirical equation very well. Considering the proportional relation between energy-level shifts and the reciprocal lattice volume (V –1), thermal expansion might be the dominant cause for energy-level shifts. We also demonstrate that the VB – defects are stable at up to 600 K. Moreover, we find that there are evident differences among different hBN nanopowders, which might originate from the local strain and distance of defects from the flake edges. Our results may provide insight into the spin properties of VB – and for the realization of miniaturized, integrated thermal sensors.