1、LETTERSPUBLISHED ONLINE:3 FEBRUARY 2013|DOI:10.1038/NPHYS2543Nanoscale magnetic imaging of a single electronspin under ambient conditionsM.S.Grinolds1,S.Hong2,P.Maletinsky1,3,L.Luan1,M.D.Lukin1,R.L.Walsworth1,4andA.Yacoby1*The detection of ensembles of spins under ambient conditionshas revolutionize
2、d the biological,chemical and physical sci-ences through magnetic resonance imaging1and nuclearmagnetic resonance2,3.Pushing sensing capabilities to theindividual-spin level would enable unprecedented applicationssuch as single-molecule structural imaging;however,the weakmagnetic fields from single
3、spins are undetectable by conven-tional far-field resonance techniques4.In recent years,therehas been a considerable effort to develop nanoscale scanningmagnetometers58,which are able to measure fewer spins bybringing the sensor in close proximity to its target.The mostsensitive of these magnetomete
4、rs generally require low tem-peratures for operation,but the ability to measure under ambi-ent conditions(standard temperature and pressure)is criticalfor many imaging applications,particularly in biological sys-tems.Herewedemonstratedetectionandnanoscaleimagingofthemagneticfieldfromaninitializedsin
5、gleelectronspinunderambient conditions using a scanning nitrogen-vacancy mag-netometer.Real-space,quantitative magnetic-field images areobtained by deterministically scanning our nitrogen-vacancymagnetometer 50nm above a target electron spin,while mea-suring the local magnetic field using dynamicall
6、y decoupledmagnetometry protocols.We discuss how this single-spin de-tectionenablesthestudyofavarietyofroom-temperaturephe-nomena in condensed-matter physics with an unprecedentedcombinationofspatialresolutionandspinsensitivity.So far,the magnetic fields from single electron spins have beenimaged on
7、ly under extreme conditions(ultralow temperaturesand high vacuum)9.Magnetometers based on negatively chargednitrogen-vacancy(NV)centres in diamond have been proposedas sensors capable of measuring individual spins1013because theycan be initialized and read-out optically14and have long coherencetimes
8、15,even under ambient conditions.Moreover,because NVcentres are atomic in size,they offer significant advantages inmagnetic resolution and sensing capabilities if they can be broughtin close proximity of targets to be measured.Recent advances indiamond nanofabrication have allowed for the creation o
9、f robustscanning probes that host individual NV centres within roughly25nmoftheirtips16.Here,weemploysuchascanningNVcentretoimagethemagneticdipolefieldofasingletargetelectronspin.Our scanning NV magnetometer(Fig.1a)consists of acombined confocal and atomic force microscope as previouslydescribed17,w
10、hich hosts a sensing NV centre embedded in adiamond nanopillar scanning probe tip16.The sensor NVs spinstate is initialized optically and read out through spin-dependentfluorescence,and its position relative to the sample is controlled1Department of Physics,Harvard University,Cambridge,Massachusetts
11、 02138,USA,2School of Engineering and Applied Science,Harvard University,Cambridge,Massachusetts,02138,USA,3Department of Physics,University of Basel,Basel,4056 Switzerland,Switzerland,4Harvard-Smithsonian Centerfor Astrophysics,Cambridge,Massachusetts 02138,USA.These authors contributed equally to
12、this work.*e-mail:yacobyphysics.harvard.edu.through atomic-force feedback between the tip and sample.Microwaves are used to coherently manipulate the sensor NV spin.Magnetic sensing is achieved by measuring the NV spins opticallydetected electron spin resonance(ESR),either by continuouslyapplying ne
13、ar-resonant microwave radiation(Fig.1b)or throughpulsed spin-manipulation schemes12,13(Fig.1c),where the sensorNV spin precesses under the influence of its local magnetic field(projected along the NV centres crystallographic orientation).We measure the contribution of the magnetic field from a targe
14、telectron spin to this precession.The entire system,including boththe scanning NV magnetometer and the target sample,operatesunder ambient conditions.To verify the single-spin detection and imaging,we choose ourtarget to be the spin associated with another negatively charged NVcentre in a separate d
15、iamond crystal(so that the sensor and targetNV centres can be scanned relative to one another).The advantageof using an NV target is that both its location and spin state can beindependently determined by its optical fluorescence.As discussedbelow,wecanthuscomparethetargetNVsmagneticallymeasuredloca
16、tion to its optically measured location and ensure that themagnetic image is from a single targeted spin.Furthermore,we canguaranteethatthetargetspinisinitializedandproperlymodulated,asisusefulforoptimizinga.c.magneticsensing.To isolate single NV targets for imaging,NV centres are createdin a shallow(25nm)layer of a bulk diamond through establishedimplantationandannealingtechniques,asusedinpreviouswork17.The target diamond surface is structured to create nanoscale mesas,whose diameters(200nm)are
