First-principles Study Of Titanium-related Defects And Preparation Of SiV~- Color Centers In Diamond

Optically active defects in diamond is the current hot topic in materials science.In order to satisfy the applications of quantum computing,quantum cryptography and optical transistors,a single photon emitter with narrow bandwidth,high repetition rate,and long coherence time is required in the future.In the field of biology,chemically stable,non-bleached and non-toxic biological markers are of great value for situ studies of biological processes.However,many of the diamond color centers have some problems to varying degrees.For example,NV color center has a wide range of fluorescence emission;Both a long lifetime of excited state and a low fluorescence yield,seriously affect its application.In recent years,transition metal elements have played an increasingly important role in diamond defects.The unique electronic structure of the transition metal atoms allows the doped diamond to have excellent luminous properties;The quasi-local phonons of the transition metal color center are not significantly coupled,which shows sharp fluorescence peaks.At the same time,the 3d-TMs are always used as solvent-catalysts to accelerate the growth of diamond crystals.Therefore,it is of great significance to explore new TM-related color centers with excellent properties.In this paper,the first-principles calculation combined with chemical vapor deposition experiments were used to study the Ti-related defects and SiV~-color center in diamond.The structure and electronic structure of the SiV~-was calculated first,we verified the structure of the Si atom was located in the center of the divacancy.The calculation of the electronic structure showed the zero-point transition energy of the SiV~-center,which was in good agreement with the experimental values,laying a foundation for subsequent calculations.Based on the optimized diamond supercell,five kinds of Ti-related diamond defect structures were constructed.It was determined that the titanium-vacancy(TiV)defect structure was the most stable configuration.The electronic structure calculation predicted that the TiV center has the emission peak at 537.8nm.In order to investigate the influence of impurities on the energy stability and electronic structure of Ti-related color centers,nitrogen and boron atoms were introduced into the supercell as co-dopants.Through the formation energy data,the possibility of co-doped defects of Ti,B,and N was determined.The electronic structure calculation results showed that the titanium-boron(Ti-B)and titanium-vacancy-tetra nitrogen(TiV-4N)defects have better band structures and may be potential luminous centers.It is predicted that their luminescence were in the infrared and visible light regions,respectively.In terms of experimental work,we have successfully prepared diamond films with Si-related color centers on the surface of quartz substrates by microwave plasma chemical deposition equipment.Through the exploration of post-treatment processes such as annealing and surface de-graphing,the prepared color center had sharp and bright luminescence with its ZPL=738nm.The position of the emission peak was fully in accordance with the literature.We explored an experimental method for synthesizing Ti-related color centers by chemical vapor deposition.A method for preparing Ti color center arrays doped with magnetron sputtering equipment was proposed.