Photoluminescence Studies Of Irradiated Defects In Diamond

Diamond,as an ultra wide band gap semiconductor material,could be used to fabricate the high-frequency high-power electronic devices with high temperature resistance.In addition,the centers of diamond have glorious application prospects in quantum information processing,biomarkers and other fields.Among them,the influence of crystal micro defects on the device macro performance,the fluorescence efficiency and stability of centers are the key research objects in these fields.Consequently,in this paper,the crystal crystallinity,stress distribution,the temperature and laser power dependence of centers were studied by Raman and photoluminescence(PL)spectroscopy.The isolated and simple intrinsic defects were introduced into pure,nitrogen and silicon doped CVD diamond by electron irradiation,and the defects were activated by annealing to diffuse in the crystal.The defect structures and the changes of centers were studied.In addition,the effect of ion implantation on diamond crystal was also studied.These researches provided theoretical and experimental basis for the application of diamond semiconductor.The main results of the paper are as follows:(1)The research on the Raman peak of diamond could provide a very high reference value for the high-quality CVD diamond and conduce to optimize the growth process.It is found that the crystal structure of pure IIa type diamond was constantly optimized during the growing process,which lead to the difference of crystal quality between the substrate surface and the interior of the crystal;due to the treatment of physical means such as cutting and polishing,the stress distribution on the crystal edge and surface of the is higher than the stress in the interior,which indicated that the crystal structure of the surface layer was poor.(2)The photoluminescence efficiency of diamond crystal defects were studied by PL spectral characterization.It was found that there were two phonon sidebands(PSB)in both nitrogen-vacancy(NV)and silicon-vacancy(Si V)centers,which was produced by multiple phonons in the energy level transition process.It indicated that the fluorescence emission of Si V center was more concentrated on the zero phonon transition,and the photoluminescence efficiency was stronger than NV center.According to Franck Condon theory,the PSB of NV and Si V centers involved monophonic and biphonic transitions,and the phonon energies were 42 me V(NV~0),67me V(NV~-)and 64 me V(Si V),respectively.In addition,NV and Si V centers exhibitd obvious temperature dependence.When the temperature was high enough,the energy levels of the ground and excited state of centers would shift and cross,which resulted in the non-radiative recombination of transitions and the zero phonon line(ZPL)s thermal quenching;the joint action of lattice deformation potential energy and electron phonon coupling led to the ZPLs red shift and the linewidth broadening.Moreover,the laser power dependence of NV and Si V centers showed that the photoluminescence process was dominated by radiative transition,with weak Auger recombination.(3)The irradiated defect structures of diamond were studied by PL spectra and annealing experiments.The temperature dependence of 515.8 nm center was quite different from that of 503.5 nm and 533.5 nm centers,which indicated 515.8 nm center was supposed to be a compound defect which composed by multi interstitials.In addition,fluorescence efficiency of NV and Si V centers were weaken after electron irradiation.Among them,The Si V and GR1 centers were convoluted into an asymmetric ZPL.After electron irradiation,the new 640 nm band was introduced into high-quality nitrogen-containing diamond.According to the studies of the temperature dependence and annealing,it concluted that the 640 nm band was related to the defect structure which recombined with interstitials and nitrogen impurities.In addition,the intrinsic defects were diffused by annealing,and the crystal damage was repaired to a certain extent.after above 700?annealing,GR1center weaken and Si V center was separated from the convolution peak;when GR1 center diffuses to the vicinity of N_s~0,and trapped by N_s~0 to form NV defects.It noted that relative intensity of NV~0 and NV~-center was affected by the content of nitrogen impurities.After irradiation and annealing,the intensity of NV~0 center was much higher than that of NV~-center in the lower nitrogen diamond;on the contrary,the intensity of NV~-center was higher in the high nitrogen diamond.(4)The Shallow level impurities were introduced into the crystal by ion implantation.Among them,the covalent radius of arsenic was too large to replace the lattice carbon atoms or enter the crystal gap,so that most of arsenic ions agglomerate together,which seriously affected the photoluminescence characterization of the crystal.In addition,there was hump loccated at 579.6nm after boron and phosphorus co-implantation,and the hump splited into D-peak and G-peak after vacuum 1350?annealing.It indicated that the crystal had a certain extent of graphitization.After 600?annealing,the D-peak and G-peak disappeared.Moreover,a new center appeared at 693.7 nm after 700?annealing,and the origin of the center still needed to be further explored.