Effects Of Stress Field On The Charge Stability Of Nitrogen Vacancy Centers In Diamond

Due to its promising applications in solid state quantum computing and quantum precisim measurement,the nitrogen-vacancy(NV)center in diamond has attracted scientific interest.Most of the applications exploit the unique spin properties of the negatively charged state of the nitrogen vcancy(NV-)center.The NV-exhibits an electron spin triplet ground state with a long coherence time,and the spin sub-level can be initialized and read optically.In contrast,the neutral state NV0 has not been viable for spin studies.However,its charge state is known to be unstable,discharging from the NV-into NV0 under various circumstance.Therefore the stability of an NV-against transforming into an NV0 is essential in real application.By first-principles calculations,we investigate the relative stability of the NV-to the NV0 in diamond under stress.We find that the ionization energy changes with stress in opposite trend of the formation energy.The applied stress is harmful for the relative stability of NV-to NV0 if only the NV center is able to reach its favorable orientation under the stress.We believe that the results are not only significant for control of the charge stability of NV center,but also enlightening for applications based on specific charge states of other kinds of defects in stress.The detailed contents and main results of this thesis are as follows:In chapter one,we introduce the background.We first introduce the physical properties and application of the NV center in diamond.Then we introduce the influence of external fields on the charge state of the NV center from experiment and theory,such as electrolytic gate electrode,photon,temperature,surface chemistry.Finally,we introduce the influence of external stress on defect and the content of this thesis is outlined.In chapter two,we introduce the research methods.We first introduce the first-principles calculations.Then we introduce the finite-size supercell correction schemes for defect calcuations,such as Makoy-Payne,band-filling correction(BFC),band-edge correction(BEC).In chapter three,we introduce the mechanical property of bulk diamond.We calculate the elastic constant.In chapter four,we introduce the physical structure and properties of the NV-and NV0 under zero stress.The NV-defect has C3v point-group symmetry and due to the Jahn-Tellar effect,NV0 has C1h point-group symmetry.In chapter five,we calculate the formation energies of the two charge states and the relative stability of the NV-to NV0 in diamond under hydrostatics,in-plane stress,uniaxial stress.We find that both the NV-and the NV0 have similar trends in their formation energies with the stress,but the formation energy of NV0 changes more evidently.It is found that once the NV center has already formed and retains its orientation,the relative stability of the NV-to NV0 can be enhanced by the compressive stress along its trigonal symmetry axis.