atom probe tomography – a high throughput screening tool of 原子探针断层–高通量筛选工具

ATOMPROBETOMOGRAPHYAHIGHTHROUGHPUTSCREENINGTOOLFORATOMICSCALECHEMISTRYKRISHNARAJANDEPARTMENTOFMATERIALSSCIENCETEL5152942670EMAILKRAJANIASTATEEDUDIFFRACTIONTOAVARIETYOFSCANNINGPROBEMETHODSAFUNDAMENTALCHALLENGEINALLTHESEMETHODS,ISTHATHIGHTHROUGHPUTDOESNOTNECESSARILYTRANSLATETOHIGHRESOLUTIONFROMOFAMICROSTRUCTURAL,CRYSTALSTRUCTUREORELECTRONICSTRUCTUREPERSPECTIVESEEFIG2DESPITETHEVASTAMOUNTOFWORKINTHEFIELDOFCOMBINATORIALMATERIALSSCIENCEANDCHEMISTRY,CHARACTERIZINGINFORMATIONWITHHIGHRESOLUTIONWHILEACQUIRINGDATAVERYFASTISSTILLACHALLENGEFIG1THESPECIMEN1ISINSERTEDINTOACRYOGENICALLYCOOLED,UHVANALYSISCHAMBERTHEANALYSISCHAMBERISCRYOGENICALLYCOOLEDTOFREEZEOUTATOMICMOTIONITISATULTRAHIGHVACUUMUHVTOALLOWINDIVIDUALATOMSTOBEIDENTIFIEDWITHOUTINTERFERENCEFROMTHEENVIRONMENTAPOSITIVEVOLTAGEISAPPLIEDTOTHESPECIMENVIAAVOLTAGE/LASERPULSETHEPOSITIVEVOLTAGEATTRACTSELECTRONSANDRESULTSINTHECREATIONOFPOSITIVEIONSTHESEIONSAREREPELLEDFROMTHESPECIMENANDPULLEDTOWARDAPOSITIONSENSITIVEDETECTORTHELOCATIONOFTHEATOMINTHESPECIMENISDETERMINEDFROMTHEIONSHITPOSITIONONTHEDETECTOR2THISCONFIGURATIONMAGNIFIESTHESPECIMENBYAMILLIONTIMESANDINDUECOURSE,ATOMSFROMTHESURFACEIONIZE,EXPOSINGANOTHERLAYEROFATOMSUNDERTHEMTHISPROCESSOFFIELDIONIZATIONCONTINUESUNTILTHESPECIMENHASBEENFULLYANALYZED,ANDPROVIDESA3DIMAGEOFTHEENTIRESPECIMENCOURTESYDSEIDMANINTHISPAPER,WEWANTTODISCUSSACHARACTERIZATIONAPPROACHTHATPROVIDESANEWANDEXCITINGAPPROACHTOHIGHTHROUGHPUTSCREENINGOFATOMICSCALECHEMISTRYATOMPROBETOMOGRAPHYTHETERMHIGHTHROUGHPUTSCREENINGCOMESINTOPLAYHEREINTHECONTEXTTHATITREFERSTOTHENATUREANDSPEEDOFDETECTINGMASSIVEAMOUNTSDATAFROMINDIVIDUALATOMS/MOLECULARFRAGMENTSATYPICALANALYSISWITHATHREEDIMENSIONALATOMPROBEDATACANCONTAINUPTOHALFABILLIONATOMSIFNOTHIGHERANDTHEDATAACQUISITIONRATECANBEEASILY100MILLIONATOMSADAYALSOASISDISCUSSEDBELOW,THATAPTCANBEINTEGRATEDWELLINTOTHESTUDYOFTWODIMENSIONALCHEMICALLIBRARYARRAYS11AKEYCHALLENGEFORATOMPROBETOMOGRAPHYISTOFABRICATEASAMPLEINTOANEEDLESHAPEWITHTIPRADIUSOF50NMFORTHESTUDYOFORGANICMATERIALS,PROBABLYTHEMOSTEFFICIENTWAYISTOCOATASHARPPREFABRICATEDNEEDLE12AMICROTIPARRAYISANORDEREDCOLLECTIONOFTALL100MICRONSIPOSTSFORMEDONASICOUPONWITHSTANDARDMICROELECTROMECHANICALSYSTEMSMEMSTECHNIQUESTHEARRAYENABLESTHEATOMPROBETOFIELDEVAPORATEATOMSEXCLUSIVELYFROMASINGLENEEDLESHAPEDSPECIMENLOCATEDAMONGAFIELDOFSIMILARNEEDLESHAPEDSPECIMENSTHESEMICROTIPARRAYSENABLETHERAPIDPREPARATIONOFALARGENUMBEROFNEARLYIDENTICALATOMPROBESAMPLESBYPROVIDINGACONSISTENTPLATFORMFORMOUNTINGTHESAMPLESECTIONONCEITISEXTRACTEDFROMTHEMATERIALOFINTERESTTHISPROVIDESAUSEFULWAYOFDEVELOPINGCOMBINATORIALARRAYSOFATOMPROBESPECIMENINTHEFOLLOWINGDISCUSSION,WEREVIEWTHELIMITEDAMOUNTOFWORKINTHEOPENLITERATURETHATADDRESSESTHEAPPLICATIONOFATOMPROBETOMOGRAPHYTOTHESTUDYOFORGANIC/BIOLOGICALMATERIALS,ESPECIALLYFROMTHEPERSPECTIVEOFHIGHTHROUGHPUTANALYSISTHISISFOLLOWEDBYASUMMARYOFTHEDATAANALYSISANDSPECIMENPREPARATIONCHALLENGESASSOCIATEDWITHBIOLOGICALSYSTEMSFORTHISKINDOFSTUDYATOMPROBETOMOGRAPHYASHIGHTHROUGHPUTSCREENINGTOOLNORMALLYATOMPROBETOMOGRAPHYISNOTCONSIDEREDASASCREENINGTOOLFORCOMBINATORIALLIBRARIESHOWEVER,WHENONECONSIDERSTHEPROCESSOFHIGHTHROUGHPUTSCREENINGOFCOMBINATORIALLIBRARIES,ONECRITICALISSUETHATISOFTENOVERLOOKED,ESPECIALLYINTERMSOFCHEMICAL/STRUCTURALCHARACTERIZATIONOFLIBRARIES,ISTHETRADEOFFBETWEENSPEEDANDSPATIALRESOLUTION/SENSITIVITYOFTHEANALYSISTHISPROBLEMBECOMESEVENMOREACUTEASTHESPATIALDENSITYOFTHEARRAYSDECREASESWITHTHECAPACITYOFUSINGNANOSCALELITHOGRAPHYTECHNIQUESASSHOWNINFIG3,ONECANPRODUCEAVERYHIGHDENSITYOF“NANOARRAYS”INSTEADOFTHEUSUALMICROARRAYSEACHTIPWITH50NMRADIUSCANSERVEEITHERASASUBSTRATEFORGENERATINGGRADIENTTHINFILMSTRUCTURESWITHEACHNEEDLEASSOCIATEDWITHASPECIFICCHEMISTRYORTHISARRAYCANBEEXTRACTED,USINGFOCUSEDIONBEAMTECHNIQUESFROMABULKMATERIALWITHKNOWNCHEMICALAND/ORMICROSTRUCTURALGRADIENTSNORMALLYIN2DIMENSIONALCOMBINATORIALLIBRARIES,ASCANNINGPROBETECHNIQUESOFTENPROVIDESTHEKEYMEANSOFSCREENINGTHELIBRARYWITHTHEATOMPROBE,WEHAVEANINASENSEA“REVERSE”GEOMETRYWHERETHESPECIMENTOBESCREENEDNEEDSTOBEINTHEFORMOFATIPANDWENEEDAWAYTOCHARACTERIZEATTHETIPOFEACHSPECIMENWITHEXTREMELYHIGHRESOLUTIONANDSENSITIVITYASSHOWINFIG2,ATOMPROBETOMOGRAPHYPROVIDESUSTHEHIGHESTLEVELOFBOTHSPATIALRESOLUTIONANDCHEMICALSENSITIVITYOFANYTECHNIQUETOANALYSESMATERIALSCHEMISTRYHENCELIBRARYGEOMETRIESTHATLENDTHEMSELVESWELLTOTHEUSEOFATOMPROBETOMOGRAPHYASAHIGHTHROUGHPUTSCREENINGTOOLFORCOMBINATORIALARRAYSINCLUDEFIG2ACOMPARATIVECHARTSHOWINGTHEVALUEOFATOMPROBETOACHIEVEBOTHCHEMICALRESOLUTIONANDCHEMICALSENSITIVITYRELATIVETOOTHERHIGHTHROUGHPUTATOMICSCALECHEMICALCHARACTERIZATIONTECHNIQUESFIG3ASILICONMICROTIPARRAYOFATOMPROBETIPSFORUSEASAPLATFORMFORDEPOSITINGCOMBINATORIALARRAYSOFFILMOVERLAYSONTHINTIPS12THINFILMGRADIENTSACROSSNANOARRAYSSUBSTRATETIPSDEVELOPINGDIFFUSIONBASEDPHASELIBRARIESONEACHTIPTOADDATHIRDDIMENSIONTOOURABILITYTOCREATECOMPOUNDLIBRARIESINTHISCASE,WEUSETHEATOMPROBETOALSOINTERROGATECHEMISTRIESINTHEVERTICALDIRECTIONALONGTHEAXISOFEACHSPECIMENTIPANEXAMPLEOFTHISISSHOWNINFIG4BELOWFORTHEDETECTIONOFCOMPOUNDPHASELIBRARIESBASEDONINTERDIFFUSIONBETWEENTHINFILMOVERL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