Towards Room Temperature Quantum Sensing of Strain in Hexagonal Boron Nitride

Abstract

Solid-state quantum emitters offer promising pathways for high-resolution, localized sensing of strain, temperature, magnetic, and electric fields. Over the past two decades, research has focused heavily on 3D bulk materials like silicon carbide and diamond Nitrogen-Vacancy (NV) centers; however, these platforms present limitations with respect to optical output and photonic device integration. Recently, 2D materials like Transition Metal Dichalcogenides (TMDs) have been found to produce quantum emission; however, their operation is limited to cryogenic temperatures. Hexagonal Boron Nitride (hBN) has emerged as a suitable candidate which offers high tunability due to its wide bandgap of ∼6 eV in its intrinsic state, high strength and flexibility with a Young’s modulus of 800 GPa, resilience to harsh thermal and chemical environments, and 2D van der Waals (vdW) structure allowing for facile integration with other materials regardless of lattice mismatch. Since the discovery of quantum emitting properties of defective hBN samples in 2016, literature focusing on sensing applications using hBN is limited, particularly in the context of micro-electromechanical systems (MEMS). This thesis demonstrates the design, simulation, and experimental implementation of an electrostatically actuated MEMS cantilever platform for modulating the optical emission wavelength of the zero-phonon line (ZPL) in defective hBN flakes. Finite element analysis (FEA) was performed to identify high strain regions of the cantilever and micro-transfer techniques were developed to deposit the flakes on those regions. Experimental characterization of nonlinear cantilever excitation revealed a bifurcation point at ∼315 kHz and photoluminescent excitation of hBN defect centers confirm a ZPL peak at ∼597 nm. These results lay the foundation for a scalable, highly sensitive strain-sensing platform capable of optical readout across a wide range of environmental conditions, including room temperature.