Investigation Of Electromagnetic Field Sensing And Fast Scanning Imaging Technology Based On A Single Spin In Diamond

Advances in science and technology are often spurred by the development of highresolution imaging approach,which allow observation of finer structures in various samples and provide unique window for the underlying mechanisms.Recently,quantum sensing has been promoting the development of high-sensitivity or high-resolution imaging techniques for decades.Nitrogen-vacancy defect(NV center)in diamond is emerging as a nanoscale quantum sensor for electric field and magnetic field;It can be operated from cryogenic temperatures to above room temperature and function over vaccum and ambient environment,allows sensor-sample distances as small as a few nanometres,exhibit a sensing bandwidth ranging from direct current to gigahertz frequencies.Moreover,as the carrier of NV centers,diamond is chemical inert.NV center,as a quantum sensor,shows compatibility in various environment such as vaccum,air,and even physiological solution.Quantum sensing based on NV centers provides a technique to measure the electric or magnetic signals in multiple researches.Focusing on investigation of the nanoscale electromagnetic imaging method,technique and applications,this dissertation develops an NV center-based method for radiofrequency(RF)electromagnetic field sensing,improves the imaging speed and quality of a self-built scanning NV center microscope(SNVM)by using a fast imaging protocol,and carries out interdisciplinary exploration in micromagnetism and geoscience on the self-built SNVM.The detailed contents is as follow:1.We propose a method for RF electromagnetic field measurement based on the forbidden magnetic dipole transition of the NV center’s ground spin triplet.We measure the amplitude of RF electric fields based on Rabi oscillation between|ms=±1>.Sensitivity of 265 V·cm-1·Hz-1/2 is achieved in our experiment.Then,we demonstrate the phase measurement of RF electric fields using the phase accumulation between |ms=±1>after continuous fliping of the electronic spin.In our experiment,the minimum phase measurement variation is 0.2°.Our method extends the NV center-based electric field sensing bandwidth from kHz to GHz,and experimentally demonstrate the electric field sensing from 13.85 MHz to 2.02 GHz.In addition,we measure the electric and magnetic components of an RF field generated by a capacitive device respectively.This work pave the way for nanoscale RF electromagnetic field imaging.2.We build a fast scanning NV center microscope.In this paper,we have achieved the fastest scanning speed of 16 ms·pixel-1 on the self-built SNVM platform using the full-hardware-triggered protocol.Our fast scanning approach improves not only the experimental efficiency,but also the imaging quality.For the scanning probe microscope,thermal drift will cause relative displacement between the probe and sample,resulting in intensively reduced imaging resolution and even distortion.Due to the shorter sampling time,our fast SNVM weakens the negative effects of thermal drift,and is expected to observe dynamic processes.3.On the self-built SNVM,we have carried out interdisciplinary researches in micomagnetism and geoscience.(a)To explore the relationship between directions of uniaxial anisotropy and magnetic domains,we obtain the stray field distribution of the surface magnetic domain of a MnNiGa bulk polycrystalline magnet.In different regions of the sample,we find two kinds of stripe domains and Neel-cap structures.The imaging results are in accordance with the micro-magnetic simulation for different tilted uniaxial anisotropy,which provides a possible new approach to magnetic domain modulation.(b)In geoscience research,We demonstrate the imaging of the stray field of a single nanoparticle in Chang’e 5 lunar sample.Single-domain(SD)magnetic particles are the most stable paleomagnetic field recorders.At present,there is no suitable means to measure the magnetic moment of a single nanoparticle in geoscience sample.In our experiment,a minimum magnetic moment of 5×10-18 A·m2 is measured.This work makes it possible to measure the magnetic properties of rare extraterrestrial samples.4.Finally,we look forward to the future development direction of SNVM in technique and interdisciplinary application.Technically,the scanning speed can be further improved by optimizing the measurement sequence,etc.In terms of application,the SNVM technique may be applied to other interdisciplinary fields such as condensed matter physics,biological studies,etc.