Ferroelectricity in thin perovskite &ampamp;#64257;lms.pdf

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1、APPLIEDPHYSICSLETTERSVOLUME75,NUMBER69AUGUST1999Ferroelectricityinthinperovskitefilmsa)T.Tybell,C.H.Ahn,andJ.-M.TrisconeDPMC,UniversityofGeneva,24QuaiE.-Ansermet,1211Geneva4,Switzerland~Received3March1999;acceptedforpublication12June1999!Wereportontheinvestigationofferroelectric

2、ityinthintetragonalsingle-crystallineperovskite®lmsofPb~Zr0.2Ti0.8)O3grownbyoff-axisrfmagnetronsputtering.Thelocalferroelectricpropertiesofatomicallysmooth®lms,withthicknessesrangingfromafewunitcellsto800Å,weremeasuredusingacombinationofelectricforcemicroscopyandpiezoelectricmi

3、croscopy.Thetimedependenceofthemeasuredsignalsrevealsastableferroelectricpolarizationin®lmsdowntothicknessesof40Å.©1999AmericanInstituteofPhysics.@S0003-6951~99!01932-4#Ferroelectricityhaslongbeenviewedasacollectivesociatedwithleakagecurrents,whichbecomesevereinex-phenomenonass

4、ociatedwithaspontaneousmacroscopicpo-tremelythinferroelectric®lms.larizationresultingfromthealignmentoflocalizeddipolesThePZT®lmsusedinthisstudyweregrownonmetallic1withinacorrelationvolume.Inthispicture,thelong-rangeNb-doped~001!SrTiO3~Nb±STO!single-crystalsubstrateselectrostat

5、icinteractionalongthepolarizationaxisfavorsthebyoff-axisradiofrequency~rf!magnetronsputtering.Theparallelalignmentofdipolesandplaysanimportantrolein®lmswerepreparedatasubstratetemperatureof;500°Cintheferroelectricinstability.Theanisotropiccharacterofthea160mTorratmosphereofO2an

6、dAr(O2/Ar:3/10).X-raydipole±dipoleinteractionimpliesananisotropiccorrelationanalysesrevealthegrowthofc-axisorientedtetragonalvolumeandanenergyperunitcellthatisconsiderablysingle-crystallinethin®lms,withac-axisparameterof4.12±higherinaperpendicularlypolarizedthin-®lmgeometrythan

7、4.18Å.Rockingcurvestakenaroundthe001PZTre¯ectioninthebulk,suggestinga®nite-sizeeffectontheferroelectricdisplayafullwidthathalfmaximum~FWHM!oflessthanproperties.Theoccurrenceofasizeeffectinthin®lms0.1°,indicativeofsampleswithahigh-crystallinequality,wouldhaveimportantimplication

8、sforapplications,sinceitandu±2uscanstakenaroundthe001r