The Development And Application Of Scanning Diamond Nitrogen-vacancy Center Microscopy

The development of the exquisite field sensitivity combined with a nanoscale spa-tial resolution of magnetic imaging techniques is of great importance to diverse areas ranging from the life sciences and condensed matter physics to cosmology.However,direct detection of magnetic fields with nanometer resolution is challenging as current state-of-the-art techniques have limited magnetic field sensitivity,spatial resolution,or incompatibility with samples.The nitrogen-vacancy(NV)center in diamond is a single electron-spin qubit with long coherence time even at room temperature,and can be initialized,manipulated,controlled and read out by laser and microwave pulses.Due to these excellent proper-ties,NV center can be utilized not only for quantum computing but also for quantum sensing and imaging.NV centers can be used as magnetic sensors with intrinsic atomic scale,the sensitivity for dc mangnetic field is about??T Hz-1/2 and for ac mangnetic field is?10nTHz-1/2,Combined optically detected magnetic resonance microscopy(ODMR)with AFM,the scanning NV microscopy(NV-SPM or SNVM)can achieve nanometer-scale spatial resolution of the magnetic field.Based on the NV centers,we can quantify the information about the stray magnetic field vector on the surface of the magnetic sample by Zeeman effect and reconstruction algorithms.In addition,the NV center is stable at temperatures ranging from 4 K to 1000 K and the magnetic field is only 1 ?T at a distance of 10 nm,so there is almost no influence with the spin textures of the sample.Therefore,NV-SPM technology has shown great potential in many areas in recent years.I have focused my efforts on three main areas during my PhD:the development and construction of the scanning NV-probe microscope,the preparation and assembly of the probe,and the scientific application of NV-SPM.This thesis is divided into the following main research phases.1.Combining quartz tuning fork-based AFM and optically detected magnetic res-onance(ODMR)technology,we built and perfected the scanning NV probe microscope independently,and made a detailed discussion on its working mode,stability,imaging methods and other techniques.2.NV center based probes are one of the most critical elements to determine the quality of N-V-SPM imaging,among which diamond probes combined with quartz tun-ing forks have been most widely used in recent years.In this thesis,we designed the diamond probe substrate in the style of an array of nanopillars(nanopillars),which has the advantages of high equivalent NV yield,simple processing into a single nanopillar probe,and can be easily disassembled and cleaned for reuse.Therefore,the new probes we designed are highly flexible and more suitable for commercial use.3.Based on the NV-SPM platform and the lab-made NV probes,I have carried out research in the following areas during my PhD.·In the biological field,we have performed high-resolution magnetic imaging of ferritin in cells,achieving 10 nm spatial resolution.This result has the potential to be applied in the early diagnosis of diseases.·In condensed matter physics,based on high-resolution magnetic domain imag-ing by NV-SPM,we have investigated the mechanism of electric field modulation of magnetic smecticons in the CoFeB system.We observed the deformation of a single skyrmion under electrical driving with a spatial resolution of a few tens of nanometers.And partial skyrmions can be created and annihilated under the cyclically tuned electric field.These results present the opportunities for illuminating the physical mechanism of strain-induced skyrmion phase transition.Besides,we give a reasonable explanation of how the local pinning effect influences the strain-controlled skyrmions.Apart from providing a unique tool to investigate this previously inaccessible phenomenon,the technique blazes a trail for the strain control of magnetic materials for future spintronic devices.·In the field of cosmology,the NV-SPM platform can explore exotic parity-odd spin-and velocity-dependent interaction beyond the Standard Model of the Universe.The quartz tuning fork adhesion to fused silica as the velocity source.The NV center as a spin makes further limits on the coupling parameters of the spin-velocity interaction model-an improvement of more than four orders of magnitude at the 200?m force range.