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<i>Ab Initio</i> Spin-Strain Coupling Parameters of Divacancy Qubits in Silicon Carbide
摘要： Cubic silicon carbide is an excellent platform for integration of defect qubits into established wafer-scale device architectures for quantum information and sensing applications, where a divacancy qubit, which is similar to the negatively charged nitrogen-vacancy (NV) center in diamond, has favorable coherence properties. We demonstrate by means of density-functional-theory calculations that for most types of distortion the 3C divacancy exhibits slightly smaller spin-strain coupling parameters but greater spin-stress coupling parameters in comparison with the diamond NV. We predict that high-quality 3C-SiC thin films hosting divacancy qubits are prospective platforms for quantum-enhanced pressure-sensor devices.
关键词： spin-strain coupling,quantum sensing,density-functional theory,divacancy qubits,silicon carbide
更新于2025-09-23 15:21:01
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-SiC
摘要： We investigate the quenching of the photoluminescence (PL) from the divacancy defect in 4H-SiC consisting of a nearest-neighbor silicon and carbon vacancies. The quenching occurs only when the PL is excited below certain photon energies (thresholds), which differ for the four different inequivalent divacancy configurations in 4H-SiC. An accurate theoretical ab initio calculation for the charge-transfer levels of the divacancy shows very good agreement between the position of the (0/?) level with respect to the conduction band for each divacancy configuration and the corresponding experimentally observed threshold, allowing us to associate the PL decay with conversion of the divacancy from neutral to negative charge state due to capture of electrons photoionized from other defects (traps) by the excitation. Electron paramagnetic resonance measurements are conducted in the dark and under excitation similar to that used in the PL experiments and shed light on the possible origin of traps in the different samples. A simple model built on this concept agrees well with the experimentally observed decay curves.
关键词： quenching,electron paramagnetic resonance,4H-SiC,divacancy,charge-transfer levels,photoluminescence
更新于2025-09-23 15:21:01
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-SiC
摘要： Optical charge state switching was previously observed in photoluminescence experiments for the divacancy defect in 4H-SiC. The participating dark charge state could not be identified with certainty. We use constrained density-functional theory to investigate the mechanism of charge state conversion from the bright neutral charge state of the divacancy defect to the positive and negative charge states including corresponding recovery of the neutral charge state. While we can confirm that the positive charge state is dark, we do not find evidence that the negative charge state is dark. We compute similar absorption energies required for conversion of the neutral defect to both charge states. However, the formation of the positive charge state requires a series of excitations involving a 2-photon excitation, while the creation of the negative charge state is achieved through a single 2-photon process. Calculated absorption energies for the recovery of the neutral defect from the positive charge state fit the experimental value better than those from the negative charge state. Defect formation energies as a function of the Fermi energy show a very small Fermi energy range in which the negative charge state is most stable, while the positive charge state exhibits a wide stability range. Overall, our computational results give more support to the identification of the dark charge state as the positive over the negative charge state in the mechanism of optical charge state switching.
关键词： divacancy defect,optical charge state switching,constrained density-functional theory,photoluminescence,4H-SiC
更新于2025-09-04 15:30:14
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Interaction Between Hydrogen and Vacancy Defects in Crystalline Silicon
摘要： Hydrogen is one of the most important impurities in silicon. It is a mobile and highly reactive species that can passivate dangling bonds at dislocations, surfaces, and interfaces, which has been widely used in the microelectronics and solar cell industry for improving device performance. Vacancy defects are elementary complexes containing dangling bonds, and the study of their interaction with hydrogen is of significant importance. In this work, the interactions of hydrogen with the vacancy-oxygen complex (VO) and the divacancy (V2) are discussed, which are the most dominant and fundamental vacancy defects stable at room temperature. It is shown that VO and V2 can interact with both atomic and diatomic hydrogen species. This complicates the interpretation of experimental data and results in different reaction paths in differently prepared samples. Besides, some of important electronic properties, particularly electronic levels for V2Hn with n > 1, are not experimentally established.
关键词： silicon,vacancy defects,vacancy-oxygen,hydrogen,divacancy
更新于2025-09-04 15:30:14