Preparation And Photoluminescence Of Germanium-Vacancy Color Center In Diamond

Diamond color center has the advantages of small size and high sensitivity,which can realize the precision measurement of spatial resolution at the nano scale.Therefore,it has a broad application prospect in the field of quantum communication and quantum sensing.Compared with nitrogen-vacancy(NV)centers,germanium-vacancy(GeV)centers have narrower zero-phonon lines,shorter fluorescence lifetime and higher luminous efficiency,which is more advantageous in quantum communication and quantum sensing.However,the current research on GeV centers mainly focuses on temperature sensors,and the photoluminescence properties of GeV centers are rarely reported.Based on this,the GeV centers were firstly prepared by ion implantation and high-temperature annealing,and then characterized by low-temperature photoluminescence spectroscopy;the effects of test temperature,laser excitation power and annealing temperature on the intensity,position,FWHM and depth distribution of the GeV centers were investigated,and the results of first-principle calculations were combined to reveal and elucidate the photoluminescence characteristics of the GeV centers and their electronic structure features.The specific results are as follows:(1)The optical transition of GeV centers is dominated by Auger recombination and radiation recombination,while the presence of nitrogen impurities changes the transition mechanism into Shockley-Read-Hall recombination between radiation recombination and defect color center.With the increase of test temperature,the peak position of GeV center zero phonon line(ZPL)has redshift and the full width at half maxima(FWHM)occurs widening.The peak redshift can be attributed to the electron-phonon coupling and the thermal softening effect of chemical bonding.The broadening of FWHM shows the homogenous broadening(Gaussian component W_G)and the inhomogeneous broadening(Lorentzian component W_L),and the W_L is consistent with the T~3 law.(2)The defect structure with the number of vacancies as a variable is calculated by using first-principle calculation.The findings show that the structure of the GeV centers is the Ge atom connected to the double-vacancy structure,and the Ge atom is connected to the surrounding six carbon atoms to form bonds.After atomic relaxation,the Ge atoms move towards the center of the vacancy.At the same time,the total energy of the structure is the lowest and the formation energy is the highest,and its impurity level exists in the form of a splitting degenerate state.Therefore,diamond exhibits shallow level p-type semiconductor characteristics,with an impurity level of approximately 1.95e V.(3)The injection range of Ge ions in diamond decreases as the injection angle increases and the peak injection damage increases.While the projection range of Ge ions increases as the injection energy increases and the peak injection damage decreases.Meanwhile,Ge ion implantation breaks the chemical bonds on the crystal surface,thus forming a black amorphous film on the implanted surface.The concentration of GeV center is different in different diamond depth directions.As the depth of diamond increases,the concentration of GeV centers gradually decreases,and the presence of nitrogen impurities can accelerate the concentration attenuation of GeV centers along the depth direction.(4)With the raising of annealing temperature,the amorphous film on the diamond of ion implantation surface gradually disappears and completely disappears at 700～750℃.At the temperature range,vacancy defects in diamond begin to move freely,diffuse to Ge atoms,and are bound to form GeV centers.Continuing to increase the annealing temperature,the intensity of GeV centers gradually increases.At the same time,the presence of nitrogen impurities in diamonds will form NV centers during the annealing process and GeV centers will interact,resulting in a decrease in GeV center strength.