| The temperature measurement method of solid-state spin Nitrogen-Vacancy(NV)color center refers to the measurement of temperature by using the spin characteristics of diamond NV.That is,the ground state energy level of the color center is transitioned under laser excitation,and the temperature is measured by obtaining the change in the D value of electron spin zero-field splitting.It is not easily limited by detection space,detection range and accuracy,and diamond has the advantages of stable fluorescence,good biocompatibility,and no toxicity,so it is a necessary measure for nano-scale temperature measurement in some specific environments,and has great practical significance and value in the research and practical application of deep-level scientific problems in biomedicine and materials science fields,such as accurately targeted therapy of tumor cells,analysis of magnetic/thermophysical properties of materials,and revelation of energy change mechanism of biochemical reactions at the micro scale.With the increasing demand for temperature measurement performance,the high-sensitivity solid-state spin NV color center temperature measurement system has been pursued by researchers at present.Some researchers have improved the sensitivity of temperature measurement to a certain extent by adjusting the spin state and optimizing the temperature-measuring device.However,as a necessary prerequisite for temperature measurement,the size and direction of magnetic field also have an important influence on the sensitivity of the measurement,which needs further study.In view of this,based on the preparation and characterization of the diamond NV color center,the design of the miniature antenna and its integration with diamond,and the influence of magnetic field on temperature measurement sensitivity,this paper studies the high-sensitivity solid-state spin NV color center temperature measurement method,so as to explore a new method and new path to effectively improve temperature measurement performance.The main research contents include:(1)Aiming at the low content of NV color center in diamond samples,a controllable and optimized preparation method using PMMA mask and N ion implantation to improve the concentration of NV color center was proposed.Through the processing operations of surface N ion implantation,high-temperature annealing and acid washing,the concentration of NV color center in the prepared diamond is increased by about 10 times,and the distribution of NV color centers in the prepared diamond is more uniform,which provides a preparation and characterization method for increasing the number of spins.(2)Aiming at the problems of large volume and low radiation efficiency of microwave antenna,a micro microwave antenna with Ω structure was designed,and an integrated method of antenna and diamond was proposed.Firstly,the Ω shaped gold thin-film microwave antenna with a thickness of 100nm was fabricated on the diamond surface by magnetron sputtering;Then,two wires of microwave antenna were generated by gold wire bonding.Through the comprehensive analysis of simulation and actual experimental data,it is found that the radiation uniformity of the designed Ω shaped microwave antenna is about 80%,the excitation efficiency of the color center is about 20 times higher than that of the traditional PCB antenna,the volume is reduced about 50%,and the sensitivity is about 400 times higher than before.(3)According to the requirements of the controllable light spot and adjustable laser power,and taking into account the high-efficiency NV color center fluorescence excitation and collection,an ensemble NV color center optical path system composed of optical precision control optical path system and the confocal system was built,which improves the excitation and collection efficiency of NV color center fluorescence;To meet the requirements of high power and wide shimming microwave radiation,a microwave system composed of microwave source,microwave power amplifier and diamond integrated antenna was designed and built.Integrated with the integrated antenna,the microwave radiation power and uniformity were improved;According to the demand for precise control of diamond temperature,the temperature control system composed of thermocouple,water cooler and PID feedback circuit improves the temperature stability and controllability through the designed temperature control feedback.(4)Based on the temperature measurement system platform built,the accuracy and sensitivity of NV color center temperature measurement under a magnetic field were studied.Firstly,the temperature measurement data under constant magnetic field and unsteady magnetic field were analyzed thoroughly.The fitting curve of the relationship between the D value and temperature T was obtained by analyzing the D value of zero-field splitting in Optical detected magnetic resonance(ODMR)spectral signals at different temperatures and magnetic fields.Then,the influence of magnetic field size and direction on temperature measurement sensitivity is discussed and analyzed,and it is found that magnetic field direction has a great influence on temperature measurement;Finally,temperature measurements were carried out under the magnetic field directions parallel to NV axis[100],[111]and[110],and the corresponding relationship between temperature and zero-field splitting D value under different magnetic field directions was summarized as dD/dT≈-45kHz/K,dD/dT≈-82kHz/K and dD/dT≈-110kHz/K.The temperature sensitivity under different magnetic field directions is estimated to be 10mK/(?)、20mK/(?)and 47mK/(?). |
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