Morphological and electrical properties of SrTiO_3TiO_2SrTiO_3 sandwich structures prepared by plasma sputtering.pdf

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1、Chin.Phys.BVol.26,No.1(2017)010702MorphologicalandelectricalpropertiesofSrTiO3/TiO2/SrTiO3sandwichstructurespreparedbyplasmasputteringSaqibJabbar1,2,†,RiazAhmad1,andPaulKChu2,†1GovernmentCollegeUniversity,Lahore54000,Pakistan2DepartmentofPhysicsandMaterialsScience,CityUn

2、iversityofHongKong,Kowloon,HongKong,China(Received5September2016;revisedmanuscriptreceived26October2016;publishedonline10December2016)SrTiO3(STO)andTiO2areinsulatingmaterialswithlargedielectricconstantsandoppositesignsofthequadraticcoefficientofvoltage(a).InsertionofaTiO2t

3、hinfilmbetweenSTOlayersincreasesthelinearityofthecapacitanceinresponsetoanappliedvoltage,tomeettheincreasingdemandoflarge-capacitance-densitydynamicrandomaccessmemorycapacitors.BothSTOandTiO2sufferfromtheproblemofhighleakagecurrentowingtotheiralmostequivalentandlowbandgape

4、nergies.Toovercomethis,thethicknessofthethinTiO2filmsandwichedbetweentheSTOfilmswasvaried.Amagnetronsputteringsystemequippedwithradiofrequencyanddirectcurrentpowersupplywasemployedfordepositingthethinfilms.TiNwasdepositedasthetopandbottommetalelectrodestoformametal–insulator

5、metal(MIM)structure,whichexhibitedaverylargelinearcapacitancedensityof21fF/um2thatdecreasedbyincreasingthethicknessoftheTiO2film.TheleakagecurrentdecreasedwithanincreaseinthethicknessofTiO2,andfora27-nm-thickfilm,themeasuredleakagecurrentwas2.01010A.X-raydiffractionandRam

6、anspectroscopyrevealedthatTiN,STO,andTiO2filmsarecrystallineandTiO2hasadominantanatesephasestructure.Keywords:strontiumtitanate,Ramanspectroscopy,plasmadeposition,MIMcapacitorPACS:07.30.Kf,52.77.Dq,74.25.nd,73.61.NgDOI:10.1088/1674-1056/26/1/0107021.Introductionkmaterialss

7、uchasTiO2,withpositivea,arebettercandi-dates.Acapacitancedensityof100fF/um2hasbeenre-Strontiumtitanate(STO)thinfilmsarepromisingfordynamicrandomaccessmemory(DRAM)capacitors,ow-portedfora(0.5nm)TiO2/(7nm)STObilayer;however,thecurrentdensitywasabove107A/cm2at1V,owingtothei

8、ngtotheirhighdielectricconstant(k)of150orhigherinthecrystallinephase,[1]goodthermalstability,go