BaNb_xTi_(1-x)O_3薄膜的电学性质及结构相变(英文)

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【关键词】钙钛矿氧化物薄膜 小极化子 金属-绝缘体转变 

【出版日期】2005-03-30

【摘要】我们利用激光分子束外延设备(L MBE)在MgO上外延生长了一系列BaNbxTi1-xO3(0 <x≤0 .5 )薄膜。X射线和Raman测量显示薄膜随Nb掺杂量的增加从四方相转变为立方相。同时电学测量表明,薄膜的导电类型从半导体转变为金属。室温电阻率随掺杂量单调下降,变化范围从1 0 1to 1 0 - 4Ω.cm。薄膜的电阻-温度曲线可以利用小极化子模型很好的拟合。这说明薄膜内的载流子主要是极化子。光电子能谱显示在BaTiO3的带隙中存在局域态,进一步说明薄膜内的载流子为极化子。

【刊名】光散射学报

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TheelectricalpropertiesandstructuralphaseevolutionsofNb -dopedBaTiO3thinfilmswithdopantcontentwereinvestigated AseriesofBaNbxTi1 -xO3(x =0 0 0 ,0 0 1 ,0 0 5 ,0 1 ,0 2and 0 5 )thinfilmswereepitaxiallygrownonMgO( 1 0 0 )singlecrystalsubstratesusingalasermolecularbeamepi taxysystem Thegrowthwascarriedoutunderlowoxygenpressureof 1 0 - 4 Patoavoidcationvacancycompensation X -raydiffractionandmicro -RamanspectroscopywereusedtoestablishthevariationofthethinfilmstructurewithNbdopingcontent TheasymmetricrockingXRDscanmeasurementsshowthatwithanincreaseofNb -dopedcontent,thelatticeparameterscandaincreasewhilec/aratiodecreases ,indi catingadecreaseoftetragonalityoftheBNTOfilms TheintensityofRamanpeaksdecreasesandthewidthofthepeaksbroadenswiththeincreasingofNb -dopedcontent TheresultsofXRDandRamanspectraindicatethatatroomtemperatureBNTOthinfilmswithNb≤ 1 0at %havetetragonalstructure ,however,forNb≥ 2 0 % at BNTOthinfilmsexhibittypicaldisorderingcubicstructure Temperaturedependenceofresistivitymeasurementclearlyshowsthemetal-insulatortransitionin ducedbyNbdopingcontent ,thatis,carrierconcentration WithNbcontentincreasing ,theresistivityvariesover 6ordersofmagnitudeatroomtemperature ,from1 0 - 4 to 1 0 2 Ω·cm Theconductingmecha nismchangesfrompolarontosemiconductortometal Thecriticaldopingcontentwasx =0 2 ;belowit,thesampleshowssemiconductorbehavior ;aboveit,thesampleshowsmetalbehavior Synchrotronradiation -basedpotoemissionspectroscopyrevealstheexistenceofimpuritybandinthebandgapofthesampleswithx≤ 0 2 Forx =0 5 ,Fermiedgewasobserved ,whichisinagreementwithitsmetallictransportingproperties Nb5 +andNb4+wasfoundtocoexistinsampleswithx =0 5bydeconvolutionoftheNb 3dcorespectroscopy Basedontheabovemeasurements ,Hubbardandpercolationmodelhavebeeninvokedtounderstandtheinsulator -metaltransition Theimpuritystatesobservedinsampleswithx≤ 0 2wereattributedtothelowerHubbardband Forx =0 5 ,theinsulatingBaTiO3isembeddedinthemetallicBaNbO3net workresultingintheobservedmetallicbehavior BaNb_xTi_(1-x)O_3薄膜的电学性质及结构相变(英文)钙钛矿氧化物薄膜;;小极化子;;金属-绝缘体转变我们利用激光分子束外延设备(L MBE)在MgO上外延生长了一系列BaNbxTi1-xO3(0 <x≤0 .5 )薄膜。X射线和Raman测量显示薄膜随Nb掺杂量的增加从四方相转变为立方相。同时电学测量表明,薄膜的导电类型从半导体转变为金属。室温电阻率随掺杂量单调下降,变化范围从1 0 1to 1 0 - 4Ω.cm。薄膜的电阻-温度曲线可以利用小极化子模型很好的拟合。这说明薄膜内的载流子主要是极化子。光电子能谱显示在BaTiO3的带隙中存在局域态,进一步说明薄膜内的载流子为极化子。

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