Diamonds Under Strain : Mapping crystal strain in synthetic diamonds using the electron spin resonance of nitrogen-vacancy centers

Sammanfattning

Solid-state defects in wide-bandgap materials offer an attractive platform for experimental quantum sensing and quantum information processing. Over the last two decades, the nitrogen-vacancy (NV) color-center defect in diamond has become one of the most widely studied systems for these quantum technologies. Historically used as a quantum sensor for magnetometry, recent progress in the field has also demonstrated the great potential of the NV center in sensing other physical quantities like electric field, temperature, or even diamond crystal strain. The precise characterization of crystal strain is of significant fundamental and technical importance in diamond-based quantum and electronic devices. This thesis establishes the NV center as an impressive tool for mapping strain in synthetic diamonds. We investigate the effect of local crystal strain on the zero-field optically detected magnetic resonance (ODMR) spectrum of NV center ensembles. The presence of strain perturbs the energy levels of the NV center, which is manifested in the ODMR spectrum as resonance frequency shifts, zero-field splittings, and the asymmetric imbalance in those splittings. We attribute the different feature changes in the ODMR spectrum to the volumetric and shear components of the local strain tensor, which is consistent with the existing theoretical spin-strain interaction model.