First-principles Study Of Diamond-doped Eu Vacancy Defects

The diamond color center has been widely studied for its stable emission spectrum,room temperature controllability,and long coherence time.Some of these color centers can not only be used as single-photon source devices with excellent performance,but also have excellent properties such as different fluorescence emission bands,narrow line width,low excited state lifetime,and high fluorescence polarization contrast.These excellent properties provide the basis for quantum information,quantum sensing and other fields.Studying the diamond color center with low excitation state lifetime,narrow fluorescence spectrum and high signal-to-noise ratio is an important subject for the research of quantum information and quantum sensing.Based on the principle of first principles,this paper studies the related properties of diamond europium related defects.The structural model of the europium atom at the center of the double vacancy(EuV)and the structural model of the europium atom’s nearest neighbors with 2 or 3 vacancies(Eu2V,Eu3V)were established respectively.By comparing and analyzing the crystal binding energy and defect formation energy,it is finally determined that the stable structure of the diamond europium vacancy color center is the structure in which the europium atom is located at the center of the double vacancy.The charge density,differential charge density,and bader charge analysis of the stable structure indicate that the europium atom is stably present in the interior of the system,and the europium atom is bonded to the adjacent six C atoms.The energy band structure and energy level structure of diamond EuV color center are analyzed.The results show that the energy band structure of diamond EuV color center has obvious spin polarization phenomenon.It is determined that the spin-up energy level structure is more suitable for the electronic excitation of diamond color center.The estimated zero-point transition energy is 1.989eV(corresponding to the photon wavelength is 623nm)and is in good agreement with the literature.It was found that the experimentally observed diamond EucV color center in the literature is consistent with the three-level structure.The actual effects of the process of depositing diamond color center EuV by chemical vapor deposition(MPCVD)in the nitrogen-rich environment were analyzed.Considering the related properties of the composite defects formed by the co-doping of B atoms,eight possible existences were established.The composite defect structure,the calculated total energy and binding energy of the established composite defect structure indicate that various composite defect structures can exist stably,analyze the energy band structure of each composite defect structure,and analyze the calculated energy band results to obtain EuV-5N is more suitable as a diamond europium related color center than other structures.The best position of the diamond EuV color center in the diamond film structure is analyzed.It is found that the best position of EuV is that the europium atom is located at the third layer from the surface.At the same time,the surface C atom dimer phenomenon of the diamond film structure is studied on the diamond EuV.The negative effects of the color center,the study found that the surface adsorption of F or H atoms can improve the negative impact of surface state on the electronic structure of the system.