Papers by Keyword: Optically Detected Magnetic Resonance

Abstract: This paper presents the development of a confocal Optically Detected Magnetic Resonance (ODMR) system to study diamond and Silicon Carbide (SiC) for reactor dosimetry and quantum defect analysis. Initially, Nitrogen-Vacancy (NV) centers in diamond were characterized to establish a performance baseline, followed by plans to map and quantify color center populations in SiC crystals before and after alpha and neutron irradiation. By correlating ODMR data with electrical performance metrics, we aim to optimize fabrication and annealing protocols to investigate fast neutron sensitivity. The ODMR system, integrated with a home-built confocal microscopy setup, includes a microwave antenna, magnet, laser, objective, and advanced measurement devices such as Si-APD and Time Tagger 20 for high-resolution T2* and T2 measurements. The characterization of the instrument includes high-resolution fluorescence and ODMR spectra of NV centers in diamond, and improved resolution with confocal optics. Ongoing work focuses on correlating luminescence with reactor neutron fluence and the long-term goal is for the advancing SiC irradiation for integrated spin defect analysis.

Abstract: We demonstrated the enhancement of the optically detected magnetic resonance (ODMR) contrast of negatively charged silicon vacancy (V_Si^-) in SiC by thermal treatment. To create high density V_Si^-, Proton Beam Writing (PBW) was conducted. After an annealing at 600 °C, ODMR contrast showed the highest value in the investigated temperature range. At a fewer irradiation fluence, despite no significant change was observed in terms of V_Si^- PL intensity, the improvement of the ODMR contrast was observed. Considering defect energy levels and annealing behavior previously reported, it was deduced that the improvement of the ODMR contrast was caused by the reduction of other irradiation induced defect centers, such as EH1/EH3 centers.

Abstract: We demonstrated optically detected magnetic resonance (ODMR) measurements using three-dimensional (3D) arrayed silicon vacancies (V_Sis) in in-plane SiC pn diodes. Proton beam writing successfully created 3D arrayed V_Sis using different ion (proton) energies. The results of PL mapping analysis indicate that the features of luminescent spot such as size and depth can be estimated by a Monte Carlo simulation (SRIM). This suggests that diagnosis at any locations in SiC devices can be realized using V_Si quantum sensors. Luminescent spots with different depth ranging 4-60 μm showed similar ODMR spectra including its contrast, which means that a similar sensor sensitivity is expected. The results suggest that 3D arrayed V_Si can act as quantum sensor elements with uniform sensitivity in SiC devices.

Abstract: We demonstrated that silicon vacancy (V_Si) can be created in SiC pn junction diode by proton beam writing (PBW) without degradation of the diode performance. The V_Si showed the same specific emission for both optically and electrically excitation, which suggests that electrically controllable V_Si was created. In addition, optically detected magnetic resonance (ODMR) signal was successfully detected from optically excited V_Si at room temperature. This result suggests that V_Si introduced into the device by PBW still maintain spin manipulating capability, which is an important step toward realizing SiC devices internally equipped with a V_Si-based quantum sensor.

Abstract: Atomic-scale defects in silicon carbide exhibit very attractive quantum properties that can be exploited to provide outstanding performance in various sensing applications. Here we provide the results of our studies of the spin-optical properties of the vacancy related defects in SiC. Our studies show that several spin-3/2 defects in silicon carbide crystal are characterized by nearly temperature independent axial crystal fields, which makes these defects very attractive for vector magnetometry. The zero-field splitting of another defect exhibits on contrast a giant thermal shift of 1.1 MHz/K at room temperature, and can be used for temperature sensing applications.

Abstract: We calculated the hyperfine structure and the zero-field splitting parameters of divacancies in 3C, 4H and 6H SiC in the ground state and in the excited state for 4H SiC within the framework of density functional theory. Besides that our calculations provide identification of the defect in different polytypes, we can find some carbon atoms next to the divacancy that of the spin polarizations are similar in the ground and excited states. This coherent nuclear spin polarization phenomenon can be the base to utilize ¹³C spins as quantum memory.