Temperature Sensing And Its Applications Based On Diamond Nitrogen-vacancy Centers

Among many physical parameters,temperature is one of the most intuitive and universal quantities with important significance in various disciplines.With the rapid advancement of science and technology,there are increasing demands for accuracy and spatial resolution in temperature measurement.For example,in the era of Moore’s Law,miniaturization of circuits and devices as well as the continuous improvement of switching speed have resulted in significant thermal gradients at sub-micrometer scales,highlighting the importance of local heating problems.In the field of life sciences,temperature is closely related to many cellular functions such as gene expression,protein stability,enzyme-ligand interactions and enzyme activity.However,there is no unified or mature method for measuring temperature at spatial scales smaller than 10 micrometers.Apart from size factors,the choice of temperature sensors usually depends on the object being measured and its environment.Therefore,developing a multifunctional temperature sensor that can meet strict requirements(such as high-temperature resistance and high-pressure resistance)will be applicable to more application scenarios.The Nitrogen Vacancy center(NV)in diamond is a stable optically luminescent defect whose energy spectrum and measurement of the electron spin quantum state can reveal information about physical quantities such as temperature,magnetic field and microwaves of the surrounding environment.Due to the excellent chemical stability and high thermal conductivity properties of diamond,this allows NV center to perform nondestructive measurements at the nanoscale.Further,the biocompatibility of diamond to cells suggests that NV center can be applied to relevant research in the life sciences.Furthermore,since NV center are host in a diamond lattice,they can be combined with techniques such as fiber optics and scanning microscopy to achieve accurate temperature measurements in different application scenarios.In this paper,the temperature nature of NV center and temperature sensing applications are investigated:1.We have developed a fiber-optic integrated system that enables fast temperature measurement based on lock-in detection.This method has twice the sensitivity compared to single-point measurements.After understanding the single-photon properties of NV center,we used polydimethylsiloxane(PDMS)transfer technology to transfer the ensemble sample onto our self-built fiber-optic integrated sensing system.We then measured the properties of the ensemble NV center using an optically detected magnetic resonance(ODMR)approach and various spin manipulation sequences,laying a foundation for temperature sensing applications.2.Using only a single NV sensor,we achieved local phase transition characterization of insulator-to-metal transition(IMT)materials.The NV center has excellent performance as a temperature sensor in fields such as life sciences,microelectronics,and thermodynamics.By utilizing the multi-functional sensing characteristics of the NV center,its application scenarios can be expanded.In IMT materials,temperature is one of the key factors triggering phase transitions.Previous studies have used magnetic field and temperature sensing of the NV center for IMT phase transition research and successfully distinguished the triggering mechanism of IMT phase transitions.Based on this research work,we designed a lock-in pulse detection sequence and in-situ characterized the temperature point location that triggers IMT phase transitions.Our detection sequence combines pulse ODMR protocol and Rabi measurement protocol to simultaneously measure physical quantities such as temperature,magnetic field,and microwave with only changing a single parameter variable.3.A time-division multiplexing technology based on post-demodulation was proposed,which decoupled temperature and magnetic field and modulate/demodulate corresponding signals in the time domain by combining with high-speed electronic switches.A pair of ODMR resonance spectra along a certain axis of NV center actually contains information about temperature and magnetic field.Existing related works utilize this feature combined with either time-division or frequency-division multiplexing technology to achieve simultaneous measurement of temperature and magnetic field.However,both methods encode the information of temperature and magnetic field onto the phase of lock-in reference signal,thus further demodulation is required to recover the signal of corresponding physical quantities.In addition to requiring data postprocessing,these two methods require precise synchronization of phases,increasing experimental difficulty.To directly obtain information about both temperature and magnetic field simultaneously,we propose a time-division multiplexing technology based on post-demodulation.Since the signal is demodulated before entering the amplifier,information about magnetic field and temperature can be read out directly without further data processing.Moreover,amplitude value measured by lock-in amplifier demodulation is independent from phase,making sensing method more stable.The method of measuring amplitude through time-division multiplexing effectively harnesses the multifunctional advantages of NV,which in turn advances the practical implementation of NV temperature sensor and broadens the range of temperature measurement applications.In summarize,this thesis demonstrates the first application of NV centers to the characterization of local phase transition temperatures at IMT.The integrated sensing capability of NV centers can provide new characterization tools for IMT material research,such as phase transition mechanism studies.In addition,this thesis proposes a post-modulation-based time-division multiplexing technology that achieves phaseinsensitive synchronous measurement of temperature and magnetic field,improving the stability of NV center measurements and reducing practical application difficulties.In the field of microelectronics,heat and magnetism often coexist,and real-time monitoring of both can provide new means for equipment failure analysis.