Supplementary Materials

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1、SupplementalMaterialsPhasestructureandfield-dependentchargeinjectionBiFeO3thinfilmswiththethicknessof200nmweredepositedon(100)SrTiO3single-crystalsubstratesat700°Cusingpulsedlaserdeposition.Duringdeposition,theflowingoxygenpressurewasadjustedtobe50mTorr,andthe

2、pulsedKrFexcimerlaserbeam(wavelength248nm)wasfocusedtoreachalaserfluenceof1-2J/cm2ontheceramictargetsurface.Fortheinvestigationoftheeffectofthefilmleakagecurrentonthepreferreddomainorientations,threeFe-enrichedbismuthferriteceramictargetswerepreparedwithnomina

3、lchemicalcompositionsofBiFeO3,BiFe1.05O3andBiFe1.1O3.WiththeincreaseintheFecontent,wecanobservethereflectionfromanimpurityphaseofBi2Fe4O9inBiFe1.1O3.1Beforeelectricalmeasurements,the150nm-thickepitaxialLaNiO3conductivelayerwaspre-grownasalowerelectrodeusingULV

4、ACACS-4000-C4magnetronsputtering.ThecrystalstructureswereinvestigatedbyX-raydiffraction(BrukerX-rayDiffractometerD8discover)withCuKa1andKbradiations,asshowninFig.S1.ThefilmsurfacewasstudiedwithaVeecoMultiMode-Vatomicforcemicroscopy(AFM)operatedintappingmode,as

5、showninFig.S2.Theplate-likegrainschangeintobigislandswithmuchrougherfilmsurfaceinreleasingepitaxialstresseswiththefurtherincreaseinthefilmthickness.2Beforemeasurements,eachfilmissusceptibletotherepetitivebipolarvoltagestressingat±10V/300nsfor10-15cyclestoachie

6、veastablemeasurement.TheuppercircularAuelectrodeswiththediametersof5-100mmweredepositedonthefilmsthroughlithography.TheinputdomainswitchingpulsesaresuppliedbyanAgilent33250Aarbitrarywaveformgeneratorwitharisetimeof5ns,andtheswitchingcurrentismonitoredthroughan

7、in-seriesLCWR6200Aoscilloscopewiththeinternalresistanceof50W.Fig.S1XRDpatternsofbismuthferritethinfilmswithdifferentFeexcesses.Fig.S2AFMmicrographofa200nm-thickBiFe1.1O3thinfilm.Theprocessofchargecompensationisdiscussedhere.Theaccumulatedoppositechargescontrad

8、ictinitialimmobiletrappedchargeswiththedensityofs0,forexample,thepositivelychargeoxygenvacanciesVO××andnegativelychargedFeFe¢(Fe3+®Fe2+)separatelypiledupneartopandbottomelectrodesw