First-principles Study Of Lanthanum-related Defects And Experimental Preparation Of Color Centers In Diamond

With the in-depth study of quantum technology,quantum information and quantum computing has become a challenging field.Diamond color centers play an important role in the quantum field,but most of the current diamond color centers have different problems and defects,which need to be improved.The wide range of fluorescence emission,low fluorescence intensity and yield,and long lifetime of excited state all affect the application of color centers.In recent years,diamond rare earth element color center plays an increasingly important role.Lanthanide is becoming more and more important due to its narrow optical transition and long spin coherence time.Due to its unique 4f layer electrons,the lanthanide elements are shielded by the5s~2,5p~6 shell electrons and weakly affected by the surrounding crystal field,which can show atomic like spectral characteristics.However,due to the effect of the odd order term of the crystal field,the 4f-4f transition restriction is removed,which makes each energy level in the 4f configuration produce sharp line spectra,showing unique and excellent optical properties.Therefore,it is of great significance to explore new color centers related to rare earth elements with excellent properties.Based on the first principles calculation method of Schrodinger equation and density functional theory,the structure,charge density and energy band of diamond La vacancy color center are simulated and analyzed by using VASP software package.Firstly,four kinds of La doped diamond defect structures are constructed,which are single vacancy,double vacancy,triple vacancy and double vacancy center.Through the analysis of relaxation,binding energy and formation energy,it is determined that the most stable structure is lav3 with La atom in the triple vacancy center.La atom is bonded with 10 surrounding C atoms,and the emission peak with lav3 center at 598.63nm.Because the experimental impurities may affect the color center of diamond La V,nitrogen(n),boron(b)and silicon(SI)atoms are introduced as Co doped impurities based on the original lav3 structure.Through the calculation of formation energy,the stability of the structure and the difficulty of formation are determined.The energy band and density of states of each structure are analyzed respectively.The calculation results of electronic structure show that B and Si impurities should be avoided.At the same time,using microwave plasma chemical vapor deposition(MPCVD)equipment,nano diamond Ce doped films were grown on quartz substrate.The vacancy was moved by high temperature annealing,and the color center was finally formed.The existence of Ce V color center was proved by laser confocal microscopy.The luminescence peak was near 498nm,which was close to the theoretical calculation results.In order to explore the preparation of La V color centers and compare the calculation and analysis,a method of preparing diamond films with La color centers by introducing doping elements into auxiliary gas was proposed.