納米氧化鋅摻雜

ZnO納米材料的可控合成是實(shí)現(xiàn)材料性能調(diào)控與應(yīng)用的基礎(chǔ)。ZnO納米材料真正走向應(yīng)用領(lǐng)域，首先需要解決的就是ZnO納米材料的可控合成問題，以獲得尺寸、形貌、結(jié)構(gòu)、單分散和重復(fù)性等穩(wěn)定可靠的ZnO納米材料。針對這個問題，人們發(fā)展了多種物理和化學(xué)的手段來合成ZnO納米材料，如氣相的熱蒸發(fā)法［1-3］、化學(xué)氣相沉積法［4-7］、脈沖激光沉積法［8-9］和液相的水熱法"-⑵、溶劑熱法［13-15］、溶膠凝膠法U6-17］、模板法［18］和微乳液法匯U9-2。］等。ZnO納米材料具有極為豐富的形貌和結(jié)構(gòu)。迄今為止，人們已經(jīng)成功地合成了各種形貌的ZnO納米結(jié)構(gòu)，如零維的納米點(diǎn)囹，一維的納米線［11］、納米棒［1。?23］、納米管［23-24］和納米帶「2］，二維的米片［25］，此外還有一些復(fù)雜的形貌如tetrapod［26-29］和納米梳［30-32］等。ZnO納米材料的摻雜半導(dǎo)體中的摻雜是指人為地將雜質(zhì)原子引入到本征半導(dǎo)體中，以調(diào)控半導(dǎo)體電學(xué)、磁學(xué)等材料性能的目的。在半導(dǎo)體工業(yè)中根據(jù)摻雜原子在半導(dǎo)體中的含量，摻雜可以分為輕摻和重?fù)剑渲休p摻的雜質(zhì)濃度在10-8數(shù)量級，而重?fù)降碾s質(zhì)濃度在0.1%數(shù)量級。當(dāng)摻雜原子的濃度更高時，一般稱為半導(dǎo)體的合金化，如SIGe、AIGaN和CulnSe:等。在研究半導(dǎo)體低維納米材料的摻雜問題時，通常納米材料中摻雜原子的濃度在千分之幾到百分之幾，有時可以達(dá)到10%以上，實(shí)際上已形成了合金，但是與傳統(tǒng)的半導(dǎo)體工業(yè)所有不同，在納米材料中引入特定的雜質(zhì)時，一般對摻雜和合金化不作細(xì)致的劃分，本文中沿用摻雜這個概念在ZnO納米材料中通過引入特定的雜質(zhì)原子可以有效地調(diào)控其光學(xué)、電學(xué)和磁性等材料性能，接下來將針對ZnO納米材料中的摻雜現(xiàn)狀作介紹。Mg、cd等摻雜在ZnO納米材料進(jìn)行Mg或Cd的摻雜，可以在納米尺度實(shí)現(xiàn)ZnO的能帶工程［33-43］。Wu等人［36］采用金屬有機(jī)化學(xué)氣相沉積方法阿(MOCVD)在高溫下成功地制備了Mg摻雜的ZnO納米棒陣列，他們系統(tǒng)地研究了Mg摻雜引起的ZnO納米棒能帶調(diào)節(jié)現(xiàn)象，Mg在ZnO納米棒中的摻雜濃度可達(dá)到16.5at.%。該方法的主要問題是Mg的金屬有機(jī)源種類非常有限，同時MOCVD需要使用昂貴的高真空設(shè)備和較高的生長溫度，在一定程度上限制了其發(fā)展。為了降低生長溫度，Lee等［44］人利用水熱方法在75一100°C生長了Mg摻雜的ZnO納米線，Mg的含量可以達(dá)到25at.%，其光學(xué)禁帶寬度在3.21一3.95eV之間可調(diào)，但是較低溫度下生長的Mg摻雜zno納米線的形貌和結(jié)晶質(zhì)量不夠理想。Ghosh等人［45］報道了采用低溫水熱的方法可以合成Cd摻雜的ZnO納米晶，隨著Cd摻雜濃度的增加，可以觀察到明顯的吸收邊紅移現(xiàn)象，但是實(shí)驗(yàn)發(fā)現(xiàn)容易出現(xiàn)CdO的分相，需要經(jīng)過分離提純才能得到Cd摻雜的ZnO納米晶。O’Brien等人［46］將金屬有機(jī)鹽在三辛胺有機(jī)溶劑中進(jìn)行熱分解反應(yīng)，得到了Mg摻雜和Cd摻雜的Zno納米晶，通過Cd或Mg的摻雜，ZnO納米晶的光學(xué)禁帶寬度可以在2.92一3.77eV之間可調(diào)，該方法的優(yōu)點(diǎn)是反應(yīng)溫度不高，獲得的摻雜ZnO納米晶具有很好的結(jié)晶質(zhì)量和可調(diào)的光學(xué)性能，但是形貌與尺寸可控性不夠理想。Mn、Ni、Co、Fe等過渡元素?fù)诫s將含有3d電子的Mn、Ni、Co和Fe等過渡元素?fù)诫s引入到ZnO材料中，可以形成所謂的稀磁半導(dǎo)體，稀磁半導(dǎo)體可能會對未來的信息存儲技術(shù)帶來變革。迄今為止，關(guān)于ZnO納米材料中Mn、Ni、CO和Fe等元素?fù)诫s和相關(guān)性能的文獻(xiàn)報道較多"68］。Kang等人［50］通過氣相熱蒸發(fā)的方法制備了Mn摻雜的ZnO納米線。Mn的摻雜濃度可以在5-20at.%之間調(diào)節(jié)，研究發(fā)現(xiàn)Mn原子成功地進(jìn)入到ZnO的晶格并占據(jù)Zn的替代位置，X射線吸收測試表明Mn摻雜的ZnO納米線在室溫下具有鐵磁性。Wang等人［68］報道了大面積襯底上生長的Ni摻雜ZnO納米棒陣列，具有優(yōu)異的晶體質(zhì)量和改善的電學(xué)性能，為研究Ni摻雜ZnO納米材料中的磁性性能提供了基礎(chǔ)。HenS等人㈣報道了Co摻雜濃度為2at.%的ZnO量子點(diǎn)，研究發(fā)現(xiàn)一部分Co原子進(jìn)入ZnO晶格并占據(jù)Zn的替代位置，大部分的Co原子(50—60%)僅僅吸附在量子點(diǎn)的表面，此外還有一部分Co原子進(jìn)入ZnO的晶格并處于間隙位置。Palomino等人㈣合成了單分散性較好的Fe摻雜ZnO納米晶，尺寸約6一8nm，研究發(fā)現(xiàn)Fe摻雜ZnO納米晶的磁性性能與納米晶的成分和尺寸密切相關(guān)。Inamdar等人［71］合成了Co摻雜和Mn、Co共摻雜的ZnO納米晶，研究發(fā)現(xiàn)ZnO納米晶中的磁性性能與ZnO納米晶中的缺陷密切相關(guān)。AI、Ga等摻雜通過III族元素如Al和Ga等原子的有效摻雜，人們可以制備n型的ZnO納米材料，顯著地提高其電導(dǎo)率和載流子濃度。Yang等人［71］采用溶劑熱的方法制備了Al摻雜的ZnO納米晶，納米晶的尺寸約為40nm，具有可控的形貌。當(dāng)Al的摻雜濃度為2at.%時，其制成的薄膜具有最低的電阻率，經(jīng)過后續(xù)的退火處理后，Al摻雜ZnO納米晶薄膜的電阻率最低可以達(dá)到22.38歐?cm，比純ZnO的電阻率低了6個數(shù)量級，研究認(rèn)為Al摻雜ZnO顯著增強(qiáng)的電導(dǎo)率是由于Al摻雜進(jìn)入了ZnO晶格并占據(jù)了Zn原子的位置。Hidayat等人［72］報道了采用低壓噴霧熱解法生長的Al摻雜ZnO納米顆粒，顆粒尺寸約為20nm，熱解溫度為800一1000°C，Al摻雜濃度為4at,%的ZnO納米顆粒薄膜經(jīng)退火處理后，在400一800nm范圍內(nèi)具有97%以上的透過率，厚度為250nm的薄膜其電阻率最低為4*103歐?cm。Hartner等人四通過化學(xué)氣相沉積方法的制備了高度結(jié)晶的Al摻雜ZnO納米顆粒，研究發(fā)現(xiàn)Al摻雜濃度在7—8at.%之間時制備的ZnO納米薄膜具有較好的電學(xué)性能，在氫氣氣氛下它的電阻率最低可以達(dá)到1.9*102歐-cm。Yuan等人網(wǎng)報道了采用簡單的CVD方法可以制備Ga摻雜的ZnO納米線，通過改變Ga的摻雜含量，即從0到1at.%，ZnO納米線的電阻率降低了兩個數(shù)量級。Wei等人［75］采用液相熱注入的方法合成了Ga摻雜的ZnO納米晶，納米晶的尺寸約為5一10nm，將Ga摻雜的ZnO納米晶旋涂成納米晶薄膜，經(jīng)過退火處理后其電阻率最低可以達(dá)到7.5*10-2歐.cm。M.H.Huang,Y.Y.Wu,H.Feick,N.Tran,E.WeberandP.D.Yang.Catalyticgrowthofzincoxidenanowiresbyvaportransport.Adv.Mater.200113(2),113一116.Z.W.Pan,Z.R.DaiandZ.L.Wang.Nanobeltsofsemiconductingoxides.Science2001,291(5510),1947-1949.B.D.Yao,Y.F.ChanandN.Wang.FormationofZn0nanostructuresbyasimplewayofthermalevaporation.Appl.Phys.Lett.2002,81(4),757-759.S.W.KimandS.Fujita.Self-organizedZn0quantumdotsonSiO}/Sisubstratesbymetalorganicchemicalvapordeposition.Appl.Phys.Lett.2002,81(26),5036-5038.YJ.Zeng,Z.Z.Ye,W.Z.Xu,L.P.ZhuandB.H.Zhao.Well-alignedZn0nanowiresgrownonSisubstrateviametal一。rganicchemicalvapordeposition.Appl.Surf.Sci.2005,250(1-4),280-283.W.I.Park,D.H.Kim,S.W.JungandGC.Yi.Metalorganicvapor-phaseepitaxialgrowthofverticallywell-alignedZn0nanorods.Appl.Phys.Lett.2002,80(22),4232-4234.B.P.Zhang,N.T.Binh,YSegawa,K.WakatsukiandN.Usami.OpticalpropertiesofZn0rodsformedbymetalorganicchemicalvapordeposition.Appl.Phys.Lett.2003,83(8),1635一1637.G.M.Fuge,T.M.S.HolmesandM.N.R.Ashfold.UltrathinalignedZn0nanorodarraysgrownbyanoveldiffusivepulsedlaserdepositionmethod.Chem.Phys.Lett.2009,479(1-3),125-127.D.Q.Yu,L.Z.Hu,J.Li,H.Hu,H.Q.Zhang,Z.W.ZhaoandQ.Fu.Catalyst-freesynthesisofZn0nanorodarraysonInP(001)substratebypulsedlaserdeposition.Mater.Lett.2008,62(25),4063-4065.B.LiuandH.C.Zeng.HydrothermalsynthesisofZn0nanorodsinthediameterregimeof50nm.J.Am.Chem.Soc.2003,125(15),4430-4431.L.E.Greene,M.Law,J.Goldberger,F.Kim,J.C.Johnson,YF.Zhang,R.J.SaykallyandP.D.Yang.Low-temperaturewafer-scaleproductionofZn0nanowirearrays.Angew.Chem.Int.Edit.2003,42(26),3031-3034.L.Vayssieres.GrowthofarrayednanorodsandnanowiresofZn0fromaqueoussolutions.Adv.Mater.2003,15(5),464-466.S.Kar,A.DevandS.Chaudhuri.SimplesolvothermalroutetosynthesizeZn0nanosheets,nanonails,andwell-alignednanorodarrays.J.Phys.Chem.B2006,110(36),17848-17853.B.Wen,Y.HuangandJ.J.Boland.ControllablegrowthofZn0nanostructuresbyasimplesolvothermalprocess.J.Phys.Chem.C2008,112(I),106一川.L.Xu,YL.Hu,C.Pelligra,C.H.Chen,L.Jin,H.Huang,S.Sithambaram,M.Aindow,R.JoestenandS.L.Suib.Zn0withdifferentmorphologiessynthesizedbysolvothermalmethodsforenhancedphotocatalyticactivity.Chem.Mater.2009,21(13),2875-2885.L.SpanhelandM.A.Anderson.Semiconductorclustersinthesol-gelprocess一quantizedaggregation,gelation,andcrystal-growthinconcentratedZn0colloids.J.Am.Chem.Soc.1991,113(8),2826-2833.VBriois,C.Giorgetti,F.Baudelet,S.Blanchandin,M.S.Tokumoto,S.H.PulcinelliandC.V.Santilli.DynamicalstudyofZn0nanocrystalandZn-HDSlayeredbasiczincacetateformationfromsol-gelroute.J.Phys.Chem.C2007,111(8),3253-3258.乙YHuo,C.K.Tsung,W.YHuang,M.Fardy,R.X.Yan,X.F.Zhang,YD.LiandP.D.Yang.Self-organizedultrathinoxidenanocrystals.NanoLett.2009,9(3),1260-1264.J.Y.Liang,GuoLin,X.H.Bin,L.Jing,L.X.Dong,W.Z.Hua,W.Z.YuandJ.Weber.AnovelsynthesisrouteandphasetransformationofZn0nanoparticlesmodifiedbyDDAB.J.Cryst.Growth2003,252(1-3),226-229.T.HiraiandY.Asada.PreparationofZn0nanoparticlesinareversemicellarsystemandtheirphotoluminescenceproperties.J.ColloidInterf.Sci.2005,284(1),184-189.Z.L.Wang.NovelnanostructuresofZn0fornanoscalephotonics,optoelectronics,piezoelectricity,andsensing.Appl.Phys.A-Mater.2007,88(1),7-15.X.D.Wang,C.J.SummersandZ.L.Wang.Large-scalehexagonal-patternedgrowthofalignedZn0nanorodsfornano-optoelectronicsandnanosensorarrays.NanoLett.2004,4(3),423-426.A.Wei,X.W.Sun,C.X.Xu,Z.L.Dong,M.$.YuandW.Huang.StablefieldemissionfromhydrothermallygrownZn0nanotubes.Appl.Phys.Lett.2006,88(2l)213102.YH.Chang,S.M.Wang,C.M.LiuandC.Chen.FabricationandCharacteristicsofSelf-alignedZn0nanotubeandnanorodarraysonSisubstratesbyatomiclayerdeposition.J.Electrochem.Soc.2010,157(11),K236-K241.A.UmarandY.B.Hahn.Zn0nanosheetnetworksandhexagonalnanodiscsgrownonsiliconsubstrate:growthmechanismandstructuralandopticalproperties.Nanotechnology2006,17(9),2174-2180.M.C.NewtonandP.A.Warburton.Zn0tetrapodnanocrystals.Mater.Today2007,10(5),50-54.Q.Wan,K.Yu,T.H.WangandC.L.Lin.Low-fieldelectronemissionfromtetrapod-likeZn0nanostructuressynthesizedbyrapidevaporation.Appl.Phys.Lett.2003,83(11),2253-2255.H.F.Li,Y.H.Huang,YZhang,J.J.Qi,X.Q.Yan,Q.ZhangandJ.Wang.Self-catalyticsynthesis,structures,andpropertiesofhigh-qualitytetrapod-shapedZn0nanostructures.Cryst.Growth&Des.2009,9(4),1863一1868.L.Shen,H.ZhangandS.W.Guo.ControlonthemorphologiesoftetrapodZn0nanocrystals.Mater.Chem.Phys.2009,114(2-3),580-583.X.YLi,F.H.Zhao,J.X.Fu,X.F.Yang,J.Wang,C.L.LiangandM.M.Wu.Double-sidedcomb-likeZn0nanostructuresandtheirderivativenanofernarraysgrownbyafacilemetalhydrothermaloxidationroute.Cryst.Growth&Des.2009,9(1),409-413.YH.Zhang,J.Liu,T.Liu,L.P.YouandX.GLi.Supersaturation-controlledsynthesisoftwotypesofsingle-sidedZn0comb-likenanostructuresbythermalevaporationatlowtemperature.J.Cryst.Growth2005,285(4),541-548.X.Tian,F.Pei,J.B.Fei,YChao,H.YLuo,D.YLuoand乙B.Pi.Synthesisandgrowthmechanism:Anovelcomb-likeZn0nanostructure.PhysicaE2006,31(2),213-217.YS.Wang.Zn0andMgxZn}_TOnanocrystalsgrownbynon-hydrolyticroute..1.Cryst.Growth2007,304(2),393-398.T.H.FangandS.H.Kang.PreparationandcharacterizationofMg-dopedZn0naporods.J.AlloyComp.2010,492(1-2),536-542.H.P.Tang,B.J.KwonandJ.Y.Park.CharacterizationsofindividualZnMgOnanowiressynthesizedbyavapor-transportmethod.Phys.StatusSolidA2010,207(11)2478-2482.C.H.Ku,H.H.ChiangandJ.J.Wu.Bandgapengineeringofwell-alignedZn,_XMg,;Onanorodsgrownbymetalorganicchemicalvapordeposition.Chem.Phys.Lett.2005,404(I-3),132-135.J.R.Wang,Z.Z.Ye,J.YHuang,Q.B.Ma,X.Q.Gu,H.P.He,L.P.ZhuandJ.GLu.ZnMgOnanorodarraysgrownbymetal-organicchemicalvapordeposition.Mater.Lett.2008,62(8-9),1263一1266.G.Chu,Z.Q.XiongandS.J.Zhao.GrowthofZn}_XMgXOandZni_aCdXONanowiresandtheApplicationinLightEmittingDevices.J.Nanosci.Nanotechno.2010,10(8),4893-4896.YS.Chang,C.T.Chien,C.W.Chen,T.YChu,H.H.Chiang,C.H.Ku,J.J.Wu,C.S.Lin,L.C.ChenandK.H.Chen.StructuralandopticalpropertiesofsinglecrystalZn}_XMgXOnanorods一Experimentalandtheoreticalstudies.J.Appl.Phys.2007,101(3),033502.G.Q.Lu,I.LieberwirthandGWegner.Ageneralpolymer-basedprocesstopreparemixedmetaloxides:ThecaseofZn}_XMgXOnanoparticles.J.Am.Chem.Soc.2006,128(48),15445-15450.YJ.Zeng,Z.Z.Ye,YF.Lu,J.GLu,L.Sun,W.Z.Xu,L.P.Zhu,B.H.ZhaoandY.Che.ZnMgOquantumdotsgrownbylow-pressuremetalorganicchemicalvapordeposition.Appl.Phys.Lett.2007,90(I),O12111.M.GhoshandA.K.Raychaudhuri.StructuralandopticalpropertiesofZn,_XMg,Onanocrystalsobtainedbylowtemperaturemethod.J.Appl.Phys.2006,100(3),034315.J.Yoo,YJ.Hong,G.C.Yi,B.ChonandT.Joo.PhotoluminescentcharacteristicsofMgXZn}_XO(0<=x<=0.18)nanorods.Semicond.Sci.Tech.2008,23(9),095015.C.YLee,T.YTseng,S.YLiandP.Lin.Single-crystallineMgXZn,_XO(0<=x<=0.25)nanowiresonglasssubstratesobtainedbyahydrothermalmethod:growth,structureandelectricalcharacteristics.Nanotechnology2005,16(8),1105一川1.M.K.Yadav,M.Ghosh,R.Biswas,A.K.Raychaudhuri,A.MookerjeeandS.Datta.Band-gapvariationinMg-andCd-dopedZn0nanostructuresandmolecularclusters.Phys.Rev.B2007,76(19),195450.YS.Wang,P.J.ThomasandP.O'Brien.OpticalpropertiesofZn0nanocrystalsdopedwithCd,Mg,Mn,andFeions.J.Phys.Chem.B2006,110(43),21412-21415.B.D.Yuhas,D.O.Zitoun,P.J.Pauzauskie,R.R.HeandP.D.Yang.Transition-metaldopedzincoxidenanowires.Angew.Chem.Int.Edit.2006,45(3),420-423.S.T.Ochsenbein,Y.Feng,K.M.Whitaker,E.Badaeva,W.K.Liu,X.S.LiandD.R.Gamelin.Charge-controlledmagnetismincolloidaldopedsemiconductornanocrystaIs.Nat.Nanotechnol.2009,4(10),681-687.O.D.Jayakumar,V.SudarsanandA.K.Tyagi.Template-assistedsynthesisofroom-temperatureferromagneticMn-dopedZnO:Firstexampleofahigh-temperaturesynthesisusingpolystyrene.Cryst.Growth&Des.2009,9(4),1944-1948.Y.J.Kang,D.S.Kim,S.H.Lee,J.Park,J.Chang,J.YMoon,G.Lee,J.Yoon,Y.JoandM.H.Jung.FerromagneticZn,_XMnXO(x=0.05,0.1,and0.2)nanowires.J.Phys.Chem.C2007,111(41),14956-14961.T.MeronandGMarkovich.FerromagnetismincolloidalMnZ+-dopedZn0nanocrystals.J.Phys.Chem.B2005,109(43),20232-20236.PV.Radovanovic,N.S.Norberg,K.E.McNallyandD.R.Gamelin.Colloidaltransition-metal-dopedZn0quantumdots.J.Am.Chem.Soc.2002,124(51)1S192-15I93.D.A.Schwartz,N.S.Norberg,Q.P.Nguyen,J.M.ParkerandD.R.Gamelin.Magneticquantumdots:Synthesis,spectroscopy,andmagnetismofCo'+一andNiz+-dopedZn0nanocrystals.J.Am.Chem.Soc.2003,125(43),13205一13218.K.R.KittilstvedandD.R.Gamelin.Activationofhigh-T}ferromagnetisminMn2+-dopedZn0usingamines.J.Am.Chem.Soc.2005,127(15),5292-5293.N.S.Norberg,K.R.Kittilstved,J.E.Amonette,R.K.Kukkadapu,D.A.SchwartzandD.R.Gamelin.SynthesisofcolloidalMn2+:Zn0quantumdotsandhigh-T}ferromagneticnanocrystallinethinfilms.J.Am.Chem.Soc.2004,126(30),9387-9398.S.A.Chambers,T.C.Droubay,C.M.Wang,K.M.Rosso,S.M.Heald,D.A.SchwartZ,K.R.KittilstvedandD.R.Gamelin.Ferromagnetisminoxidesemiconductors.Mater.Today2006,9(11),28-35.K.R.KittilstvedandD.R.Gamelin.Manipulatingpolarferromagnetismintransition-metal-dopedZnO:Whymanganeseisdifferentfromcobalt(invited).J.Appl.Phys.2006,99(8),08M112.E.Badaeva,YFeng,D.R.GamelinandX.S.Li.InvestigationofpureandCo'+-dopedZn0quantumdotelectronicstructuresusingthedensityfunctionaltheory:choosingtherightfunctional.NewJ.Phys.2008,10,055013.M.A.White,S.T.OchsenbeinandD.R.Gamelin.ColloidalnanocrystalsofwurtziteZn}_}CoXO(0<=x<=1):Modelsofspinodaldecompositioninanoxidedilutedmagneticsemiconductor.Chem.Mater.2008,20(22),7107-7116.D.W.Wu,Z.B.Huang,G.F.Yin,Y.D.Yao,X.M.Liao,D.Han,X.HuangandJ.W.Gu.Preparation,structureandpropertiesofMn-dopedZn0rodarrays.Crystengcomm.2010,12(I),192-198.K.JugandV.A.Tikhomirov.ComparativeStudiesofcationdopingofZn0withMn,Fe,andCo.J.Phys.Chem.A2009,113(43),11651—11655.E.Badaeva,C.M.Isborn,YFeng,S.T.Ochsenbein,D.R.GamelinandX.S.Li.TheoreticalCharacterizationofelectronictransitionsinCot+—andMn'、+-dopedZn0nanocrystals.J.Phys.Chem.C2009,113(20),8710-8717.L.B.Duan,G.H.Rao,J.Yu,Y.C.Wang,W..GChuandL.N.Zhang.StructuralandmagneticpropertiesofZn}_XMnXO(0<=x<=0.40)nanoparticles.J.Appl.Phys.2007,102(10),103907.O.D.Jayakumar,H.G.Salunke,R.M.Kadam,M.Mohapatra,G.YaswantandS.K.Kulshreshtha.MagnetisminMn-dopedZn0nanoparticlespreparedbyaco-precipitationmethod.Nanotechnology2006,17(5),1278-1285.L.W.Yang,X.L.Wu,G.S.Huang,T.Qiuand.YM.Yang.InsitusynthesisofMn-dopedZn0multilegnanostructuresandMn-relatedRamanvibration.J.Appl.Phys.2005,97(1),014308.R.K.Zheng,H.Liu,X.X.Zhang,VA.L.RoyandA.B.Djurisic.ExchangebiasandtheoriginofmagnetisminMn-dopedZn0tetrapods.Appl.Phys.Lett.2004,85(13),2589-2591.H.He,C.S.Lao,L.J.Chen,D.Davidovicand乙L.Wang.Large-sc