Understanding the optical properties of color centers in silicon carbide is essential for their use in quantum technologies,such as single-photon emission and spin-based qubits.In this work,first-principles calculatio...Understanding the optical properties of color centers in silicon carbide is essential for their use in quantum technologies,such as single-photon emission and spin-based qubits.In this work,first-principles calculations were employed using the r^(2)SCAN density functional to investigate the electronic and vibrational properties of neutral divacancy configurations in 4H-SiC.Our approach addresses the dynamical Jahn–Teller effect in the excited states of axial divacancies.By explicitly solving the multimode dynamical Jahn–Teller problem,we compute emission and absorption lineshapes for axial divacancy configurations,providing insights into the complex interplay between electronic and vibrational degrees of freedom.The results show strong alignment with experimental data,underscoring the predictive power of the methodologies.Our calculations predict spontaneous symmetry breaking due to the pseudo Jahn–Teller effect in the excited state of the kh divacancy,accompanied by the lowest electron–phonon coupling among the four configurations and distinct polarizability.These unique properties facilitate its selective excitation,setting it apart from other divacancy configurations,and highlight its potential utility in quantum technology applications.These findings underscore the critical role of electron–phonon interactions and optical properties in spin defects with pronounced Jahn–Teller effects,offering valuable insights for the design and integration of quantum emitters for quantum technologies.展开更多
The diffusion mechanism of boron in bcc-Fe has been studied by first-principles calculations. The diffusion coefficients of the interstitial mechanism, the B-monovacancy complex mechanism, and the B-divacancy complex ...The diffusion mechanism of boron in bcc-Fe has been studied by first-principles calculations. The diffusion coefficients of the interstitial mechanism, the B-monovacancy complex mechanism, and the B-divacancy complex mechanism have been calculated. The calculated diffusion coefficient of the interstitial mechanism is DO = 1.05 x l0-7 exp （-0.75 eV/kT） m2. s-1, while the diffusion coefficients of the B-monovacancy and the B-divacancy complex mechanisms are D1 =1.22 x 10-6fl exp （-2.27 eV/kT） mE. s-1 and D2 - 8.36 x 10-6 exp （-4.81 eV/kT） m2. s-l, re- spectively. The results indicate that the dominant diffusion mechanism in bcc-Fe is the interstitial mechanism through an octahedral interstitial site instead of the complex mechanism. The calculated diffusion coefficient is in accordance with the reported experiment results measured in Fe-3%Si-B alloy （bcc structure）. Since the non-equilibrium segregation of boron is based on the diffusion of the complexes as suggested by the theory, our calculation reasonably explains why the non-equilibrium segregation of boron is not observed in bcc-Fe in experiments.展开更多
The chemical vapor deposition (CVD) process can produce single or poly-crystalline diamond samples of high purity or with controlled doping concentrations. The defect type in the CVD diamonds can be changed by heating...The chemical vapor deposition (CVD) process can produce single or poly-crystalline diamond samples of high purity or with controlled doping concentrations. The defect type in the CVD diamonds can be changed by heating the samples. Controlling the defect type can be used to create devices for quantum diamond switches that could be used in radiation sensors and quantum information technology. Eight samples of CVD diamonds were analyzed with Doppler broadening of positron annihilation radiation (DBAR) before and after annealing in high vacuum with an electron gun. Between temperatures of 1700 - 1850 K, nitrogen was liberated from the diamond sample. At these high temperatures, the surface was graphitized and a change in the color and transparency of the diamond was observed. Some of the samples were analyzed with DBAR during periods with and without light. The defect properties were observed to change depending on the time exposure to the positron beam and were then regenerated by exposure to light. The DBAR data is compared to photoluminescence data and a time varying defect state is discussed for detector and optical grade type II CVD diamonds.展开更多
This paper reports results from an investigation of the interaction of displaced Si-self atoms (I) and their vacancies (V), with impurities in crystalline silicon (Si), as induced by micro-second pulse duration irradi...This paper reports results from an investigation of the interaction of displaced Si-self atoms (I) and their vacancies (V), with impurities in crystalline silicon (Si), as induced by micro-second pulse duration irradiation with electrons at different energies: 3.5, 14, 25 and 50 MeV and pico-second pulse duration with energy 3.5 MeV. V-V, I-impurity atom and V-impurity atom interactions are analyzed both experimentally and as modeled using computer simulations. A process of divacancy (V2) accumulation in the dose-dependent linear region is investigated. The effect of impurities on recombination of correlated divacancies, and I-atoms that had become displaced from regular lattice points is estimated by computer modeling of an appropriate diffusion-controlled process. It is concluded that the experimental results can be interpreted quantitatively in terms of a strongly anisotropic quasi-one-dimensional diffusion of displaced I-atoms. In addition, a significant difference is found between the effects of pico-second duration electron beam irradiation, which causes the formation of A-centre (V + Oxygen) clusters, while when the beam is applied on a micro-second timescale, divacancies are created instead, although the electrons have the same energy in both cases.展开更多
基金support was kindly provided by the Research Council of Norway and the University of Oslo through the frontier research project QuTe(No.325573,FriPro ToppForsk-program)The work of MEB was supported by an ETH Zürich Postdoctoral Fellowship.Computational resources were provided by supercomputer GALAX of the Center for Physical Sciences and Technology,Lithuania,and the High Performance Computing Center“HPC Saulėtekis”in the Faculty of Physics,Vilnius University.
文摘Understanding the optical properties of color centers in silicon carbide is essential for their use in quantum technologies,such as single-photon emission and spin-based qubits.In this work,first-principles calculations were employed using the r^(2)SCAN density functional to investigate the electronic and vibrational properties of neutral divacancy configurations in 4H-SiC.Our approach addresses the dynamical Jahn–Teller effect in the excited states of axial divacancies.By explicitly solving the multimode dynamical Jahn–Teller problem,we compute emission and absorption lineshapes for axial divacancy configurations,providing insights into the complex interplay between electronic and vibrational degrees of freedom.The results show strong alignment with experimental data,underscoring the predictive power of the methodologies.Our calculations predict spontaneous symmetry breaking due to the pseudo Jahn–Teller effect in the excited state of the kh divacancy,accompanied by the lowest electron–phonon coupling among the four configurations and distinct polarizability.These unique properties facilitate its selective excitation,setting it apart from other divacancy configurations,and highlight its potential utility in quantum technology applications.These findings underscore the critical role of electron–phonon interactions and optical properties in spin defects with pronounced Jahn–Teller effects,offering valuable insights for the design and integration of quantum emitters for quantum technologies.
基金Project supported by the National Natural Science Foundation of China(Grant No.51276016)the National Basic Research Program of China(Grant No.2012CB720406)
文摘The diffusion mechanism of boron in bcc-Fe has been studied by first-principles calculations. The diffusion coefficients of the interstitial mechanism, the B-monovacancy complex mechanism, and the B-divacancy complex mechanism have been calculated. The calculated diffusion coefficient of the interstitial mechanism is DO = 1.05 x l0-7 exp （-0.75 eV/kT） m2. s-1, while the diffusion coefficients of the B-monovacancy and the B-divacancy complex mechanisms are D1 =1.22 x 10-6fl exp （-2.27 eV/kT） mE. s-1 and D2 - 8.36 x 10-6 exp （-4.81 eV/kT） m2. s-l, re- spectively. The results indicate that the dominant diffusion mechanism in bcc-Fe is the interstitial mechanism through an octahedral interstitial site instead of the complex mechanism. The calculated diffusion coefficient is in accordance with the reported experiment results measured in Fe-3%Si-B alloy （bcc structure）. Since the non-equilibrium segregation of boron is based on the diffusion of the complexes as suggested by the theory, our calculation reasonably explains why the non-equilibrium segregation of boron is not observed in bcc-Fe in experiments.
文摘The chemical vapor deposition (CVD) process can produce single or poly-crystalline diamond samples of high purity or with controlled doping concentrations. The defect type in the CVD diamonds can be changed by heating the samples. Controlling the defect type can be used to create devices for quantum diamond switches that could be used in radiation sensors and quantum information technology. Eight samples of CVD diamonds were analyzed with Doppler broadening of positron annihilation radiation (DBAR) before and after annealing in high vacuum with an electron gun. Between temperatures of 1700 - 1850 K, nitrogen was liberated from the diamond sample. At these high temperatures, the surface was graphitized and a change in the color and transparency of the diamond was observed. Some of the samples were analyzed with DBAR during periods with and without light. The defect properties were observed to change depending on the time exposure to the positron beam and were then regenerated by exposure to light. The DBAR data is compared to photoluminescence data and a time varying defect state is discussed for detector and optical grade type II CVD diamonds.
文摘This paper reports results from an investigation of the interaction of displaced Si-self atoms (I) and their vacancies (V), with impurities in crystalline silicon (Si), as induced by micro-second pulse duration irradiation with electrons at different energies: 3.5, 14, 25 and 50 MeV and pico-second pulse duration with energy 3.5 MeV. V-V, I-impurity atom and V-impurity atom interactions are analyzed both experimentally and as modeled using computer simulations. A process of divacancy (V2) accumulation in the dose-dependent linear region is investigated. The effect of impurities on recombination of correlated divacancies, and I-atoms that had become displaced from regular lattice points is estimated by computer modeling of an appropriate diffusion-controlled process. It is concluded that the experimental results can be interpreted quantitatively in terms of a strongly anisotropic quasi-one-dimensional diffusion of displaced I-atoms. In addition, a significant difference is found between the effects of pico-second duration electron beam irradiation, which causes the formation of A-centre (V + Oxygen) clusters, while when the beam is applied on a micro-second timescale, divacancies are created instead, although the electrons have the same energy in both cases.
