Photoluminescence Studies On The Charge States Of Nitrogen-Vacancy Defects In Diamond

Diamond has the advantages of wide band gap,high thermal conductivity,high carrier mobility,high intrinsic temperature and high breakdown voltage.It has broad application prospects in the fields of electronic devices,high-frequency microwave devices and high-temperature high-power devices.Nitrogen is the most common impurity atom in diamond,and it is ubiquitous in natural and synthetic diamonds.Therefore,the study of nitrogen-doped diamond has important research significance.It will cause lattice distortion that the presence of nitrogen impurities in the crystal,and there is often a vacancy in its adjacent position,that is,a nitrogen-vacancy defect(NV center).The NV center not only has stable optical properties,but more importantly,it is an ideal qubit at room temperature.However,these excellent properties only belong to the negatively charged NV~-center,not the neutral NV°center.Therefore,controlling the charge states of the NV center has important research significance.This thesis uses photoluminescence spectroscopy to study the irradiation annealing control of the NV center charge states in nitrogen-doped diamond,revealing the influence of nitrogen content,annealing temperature,excitation power,and measurement temperature on the NV center charge states.The transformation mechanism of the charge states of the NV center is clarified,which provides theoretical support for the application of the NV center in the fields of magnetic field detection,temperature detection and spin detection.The specific results are as follows:(1)The charge state of the NV center depends on the distance between the NV°center and the impurity nitrogen atom.The higher the nitrogen content,the smaller the distance between the NV°center and the nitrogen atom,and it is easier for the NV°center to obtain electrons from nearby impurity nitrogen and convert it into NV~-center.As the annealing temperature increases,the charge state balance between the NV centers is gradually broken.The higher the nitrogen content,the more the NV°center tends to acquire electrons and the conversion into NV~-center;conversely,the more the NV~-center tends to lose electrons and convert it into NV°center.(2)The 563.2 nm,579.4 nm and 596.5 nm zero phonon lines are probably caused by nitrogen-interstitial atom related defects.After the 400～600℃annealing,the interstitial atoms will escape the bondage of nitrogen impurities and diffuse to the vacancies and annihilate.After the temperature continues to700℃,the vacancies will move freely at this time and diffuse to the nitrogen impurity where they are bound to form an NV center.(3)As the increase of excitation power,the low nitrogen content makes the NV~-center more likely to undergo Auger recombination during the transition process,so that NV~-is converted into NV°center;high nitrogen content will inhibit NV~-center undergoes Auger recombination,and the resonance excitation of the NV°center helps to capture electrons to form the NV~-center.(4)As the measurement temperature increases,the NV center is more likely to release energy in the form of emitted phonons during the transition process,so that its intensity will be quenched.While the NV~-/NV°intensity ratio in low-nitrogen diamond does not change with the measurement temperature,which shows that the NV~-/NV°intensity ratio can be accurately measured at room temperature for the low-nitrogen diamond.