V. A. Soltamov

Room temperature coherent spin alignment of silicon vacancies in 4H- and 6H-SiC.

We report the realization of the optically induced inverse population of the ground-state spin sublevels of the silicon vacancies (V(Si)) in silicon carbide (SiC) at room temperature. The data show that the probed silicon vacancy spin ensemble can be prepared in a coherent superposition of the spin states. Rabi nutations persist for more than 80 μs. Two opposite schemes of the optical alignment of the populations between the ground-state spin sublevels of the silicon vacancy upon illumination with unpolarized light are realized in 4H- and 6H-SiC at room temperature. These altogether make the silicon vacancy in SiC a very favorable defect for spintronics, quantum information processing, and magnetometry.

Magnetic field and temperature sensing with atomic-scale spin defects in silicon carbide

Quantum systems can provide outstanding performance in various sensing applications, ranging from bioscience to nanotechnology. Atomic-scale defects in silicon carbide are very attractive in this respect because of the technological advantages of this material and favorable optical and radio frequency spectral ranges to control these defects. We identified several, separately addressable spin-3/2 centers in the same silicon carbide crystal, which are immune to nonaxial strain fluctuations. Some of them are characterized by nearly temperature independent axial crystal fields, making these centers very attractive for vector magnetometry. Contrarily, the zero-field splitting of another center exhibits a giant thermal shift of −1.1u2005MHz/K at room temperature, which can be used for thermometry applications. We also discuss a synchronized composite clock exploiting spin centers with different thermal response.

Optically Addressable Silicon Vacancy-Related Spin Centers in Rhombic Silicon Carbide with High Breakdown Characteristics and ENDOR Evidence of Their Structure.

We discovered a family of uniaxially oriented silicon vacancy-related centers with S=3/2 in a rhombic 15R-SiC crystalline matrix. We demonstrate that these centers exhibit unique characteristics such as optical spin alignment up to the temperatures of 250°C. Thus, the range of robust optically addressable vacancy-related spin centers is extended to the wide class of rhombic SiC polytypes. To use these centers for quantum applications it is essential to know their structure. Using high frequency electron nuclear double resonance, we show that the centers are formed by negatively charged silicon vacancies V_{Si}^{-} in the paramagnetic state with S=3/2 that is noncovalently bonded to the neutral carbon vacancy V_{C}^{0} in the nonparamagnetic state, located on the adjacent site along the SiC symmetry c axis.

Temperature-scanned magnetic resonance and the evidence of two-way transfer of a nitrogen nuclear spin hyperfine interaction in coupled NV-N pairs in diamond

New method for the detection of magnetic resonance signals versus temperature is developed on the basis of the temperature dependence of the spin Hamiltonian parameters of the paramagnetic system under investigation. The implementation of this technique is demonstrated on the nitrogen-vacancy (NV) centers in diamonds. Single NV defects and their ensembles are suggested to be almost inertialess temperature sensors. The hyperfine structure of the 14N nitrogen nuclei of the nitrogen-vacancy center appears to be resolved in the hyperfine structure characteristic of the hyperfine interaction between NV and an Ns center (substitutional nitrogen impurity) in the optically detected magnetic resonance spectra of the molecular NV-Ns complex. Thus, we show that a direct evidence of the two-way transfer of a nitrogen nuclear spin hyperfine interaction in coupled NV-Ns pairs was observed. It is shown that more than 3-fold enhancement of the NV optically detected magnetic resonance signal can be achieved by using water as a collection optics medium.

Diagnostics of NV defect structure orientation in diamond using optically detected magnetic resonance with a modulated magnetic field

A method for determining the orientation of nitrogen-vacancy (NV) defect structure orientation in diamond crystals and nanodiamonds is proposed, which is based on the optically detected magnetic resonance technique with magnetic field modulation and microwave frequency scanning.

Point Defects in SiC as a Promising Basis for Single-Defect, Single-Photon Spectroscopy with Room Temperature Controllable Quantum States

The unique quantum properties of the nitrogen–vacancy (NV) center in diamond have motivated efforts to find defects with similar properties in silicon carbide (SiC), which can extend the functionality of such systems not available to the diamond. As an example, results of experiments on electron paramagnetic resonance (EPR) and optically detected magnetic resonance (ODMR) are presented suggests that silicon vacancy (VSi) related point defects in SiC possess properties the similar to those of the NV center in diamond, which in turn make them a promising quantum system for single-defect and single-photon spectroscopy in the infrared region. Depending on the defect type, temperature, SiC polytype, and crystalline position, two opposite schemes have been observed for the optical alignment of the high-spin ground state spin sublevels population of the VSi-related defects upon irradiation with unpolorized light. Spin ensemble of VSi-related defects are shown to be prepared in a coherent superposition of the spin states even at room temperature. Zero-field (ZF) ODMR shows the possibility to manipulate of the ground state spin population by applying radiofrequency field. These altogether make VSi-related defects in SiC very favorable candidate for spintronics, quantum information processing, and magnetometry.

An optical quantum thermometer with submicrometer resolution based on the level anticrossing phenomenon

An optical quantum thermometer with submicrometer resolution is proposed. Its operation is based on the physical phenomenon of the optical response in a system of spin centers in silicon carbide under conditions of anticrossing of spin sublevels of the excited quadruplet state (S = 3/2) with temperature-dependent fine-structure splitting.

Point defects in silicon carbide as a promising basis for spectroscopy of single defects with controllable quantum states at room temperature

The spin and optical properties of silicon vacancy defects in silicon carbide of the hexagonal 6H polytype have been investigated using photoluminescence, electron paramagnetic resonance, and X-band optically detected magnetic resonance. It has been shown that different configurations of these defects can be used to create an optical alignment of their spin sublevels as in the case of low temperatures and at temperatures close to room temperature (T = 293 K). The main specific feature of silicon vacancy centers in silicon carbide is that the zero-magnetic-field-splitting parameter of some centers remains constant with variations in the temperature, which indicates prospects for the use of these centers for quantum magnetometry. It has also been shown that a number of centers, on the contrary, are characterized by a strong dependence of the zero-magnetic-field-splitting parameter on the temperature, which indicates prospects for the use of these centers as temperature sensors.

Structural Perfection of Silicon Carbide Crystals Grown on Profiled Seeds by Sublimation Method

— The distribution of extended defects in silicon carbide (SiC) crystals grown on profiled seeds by the sublimation (physical vapor transport) method has been studied by optical microscopy in combination with chemical etching and AFM. It is established that free lateral growth on protruding relief elements (mesas) is accompanied by a sharp decrease in the density of threading dislocations and micropipes. The decreased density of dislocations is retained after growing a thick layer that involves the overgrowth of grooves that separated individual mesas.

Influence of neutron irradiation on etching of SiC in KOH

The effect of reactor neutron irradiation on the etch rate of SiC in potassium hydroxide has been studied. In the case of high irradiation doses (1019–1021 cm–2), the etch rate of silicon carbide has been shown to drastically rise, especially in the [0001]Si direction. This considerably mitigates the orientation anisotropy of polar face etching. After high-temperature annealing (up to 1200–1400°C), a higher etch rate of irradiated crystals persists. The results have been explained by the high concentration of radiation-induced (partially clustered) defects they contain.