线性正磁电阻材料硒化银的制备工艺及性能研究

华中科技大学硕士学位论文线性正磁电阻材料硒化银的制备工艺及性能研究姓名：李丽娟申请学位级别：硕士专业：凝聚态物理指导教师：杨凤霞20090501I(1K-300K)(1mT~60T)LMR60TLMR(2ge0ASδδ≥)SeXRDSEM,10hα500XRDSEMSe75%2geASδeg2SAδ2geASn1.56~1.97eV105K~293K1.73T10%Se75%eg2SAδIIAbstractSelf-dopednonstoichiometricsilverchalcogenideshaveattractedlotsofattentionduetotheirunusuallylarge,positiveandlinearmagnetoresistanceeffect(LMR),whichexhibitsalineardependenceonmagneticfieldinawidetemperaturerange(1K-300K)andwiderangeofmagneticfield(1mT~60T).Especially,LMRhasnosaturationatthehighmagneticfieldupto60T.Inthisthesis,bothstoichiometricandnonstoichiometricsilverselenide(2ge0ASδδ≥)crystalshavebeensuccessfullysynthesizedbythetwo-stepmethodforthefirsttime.Thestructureandmorphologyofthesampleswereanalyzed,theoptimalpreparationconditioneswereinvestigated,andtheirphysicalpropertieswerestudied.Firstly,seleniumproportioninchemicalequationwaschangedandsilverselenidenanoparticleswithdifferentsilverexcess(2ge0ASδδ≥)weresynthesizedbyroomtemperaturemethod,andthenweresinteredintocrystalsbysolidstatemethod.TheresultsofXRDandSEMindicatedthat10histheoptimalreactiontimewiththeresultofhigh-purity2SeAgδα+−nanoparticlesand500isthebestsinteringtemperaturewiththeresultofcompleted-crystallized2SeAgδ+crystals.Moreover,thedenseofcrystalswereimprovedwhensinteredinflowingargonofcrystalsaswellastreatedtothenanoparticlesbeforesintered.Secondly,X-raydiffractionandscanningelectronmicroscopywereusedtocharacterizethemicrostructureof2SeAgδ+crystals.Theresultsshowedthat,withthereducingSeinmixtureratio,thesizeofcrystalreducedandthereweremoreexcesssilverwhichexistsasatomsorclustersandarrangedchainlikeinthesilverselenidematrix.Moreover,thephysicalpropertiesof2SeAgδ+wereanalyzedbyusingvarioustestIIImethods.Theresultsindicatedthat2SeAgδ+crystalsweren-typesmall-gapsemiconductorswithbandgapenergiesof1.56~1.97eV,amongsamples,thebandgapofnonstoichiometric2SeAgδ+wasslightlyhigherthanthoseofAg2Se;withincreasedtemperature,theelectricconductivityofcrystalsincreasedatfirstandarrivedatamaximum,thenreducedrapidly,whichiscoordinatedwiththeconductivity-temperatureproperofdopedsemiconductor;apositiveandlinearMReffectwasdiscoveredsurprisinglywithalargeMReffectupto10%atroomtemperatureandmagneticfieldsof1.73T.Also,theMReffectof2SeAgδ+crystalswasimprovedandthetransitionfieldfromOMRtoLMRwasreducedwithreducedproportionofSeinmixtureratio(75%).Keywords:silverselenide,nonstoichiometric,two-stepmethod,linearmagnetoresistanceeffect___1119881994IBM1.11.1.1(MagnetoresistanceEffectMR)(0,)ρT(,)HTρTH(,)(0,)HTTρρρ∆=−(,)(0,)100%HTTMRρρρρρ∆−==×ρ(0,)ρT(,)HTρMR0MR0ρ∆2HJ()(0)Hρρρ⊥⊥⊥∆=−()(0)Hρρρ∆=−PPP1.1.2(OrdinaryMagnetoresistanceOMR)OMRThomson[1]1857(AnisotropicMagnetoresistanceAMR)1971Hunt[2]1985IBMAMR1988M.N.Baibich[3]Fe/Cr4.2K2T50%Fe/Ni(GiantMagnetoresistanceGMR)B.Dieny[4]///(spin-valve)(NiFe/Cu/NiFe/FeMn)GMR1994La-Ca-Mn-O[5]106~108%(ColossalMagnetoresistanceCMR)1995Miyazaki[6]Fe/Al2O3/Fe15.6%(TunnelMagnetoresistanceTMR)3TMR1968(K)[7-12](Na)[8](Al)[13](In)[14-15](LinearMagnetoresistanceLMR)InSb[16]PbTe[17]Ge[18]LMR[19]1997Xu[20](2AgSeδ+)(2AgTeδ+)LMRLMR5.5T120%4.5K300KmT60T60TLMR1.1.3(OMR)(AMR)(GMR)(CMR)(TMR)(LMR)OMRAMRGMRCMRTMRLMR41.21.2.1[21]αβ133°C()140°C()[22]2(,)AgXSeTeα−Junod[23]0K2AgXα−00.075EeV=2AgXα−[24]2AgXβ−[25]2(,)AgXSeTeβ−[26-28]1.2.2Xu[20]1997Xuδ=0.010.33mol124.5K5.5T370%12034.5K300KmT5.5T45.5T5(OMR)(LMR)LMR2000Schnyders[29]435101.210δ−−−××2TAgeδ+Agn5.5T350%2002Husman[30]60T130K55T2000%G.Beck[31-34]40.7910δ−×2AgSeOMR420.791010δ−−×(LMR)210δ−OMR2005Kreutzbruck[35]xAgSe(1.5x18)2X2.52T4T~10T2007B.Mogwitz[36]2.47AgSe2~3T10nmChicagoArgonneCambridge6Husman[34]60T23T[37]1.2.31.2.3.1Ag2SeH2Se[38][39-42][43][44-45]Henshaw[42][46-53]()M.Ferhat[54]1273K2AgSe[55][56]2000JunqingHu[57]SeAgClNaOH72AgSeβ−2004[58]1202AgSeNaSeO32AgSeSeS.K.Batabyal[59]2AgSe2AgSeM.Kreutzbrucka[35]PLDPVD2AgSeB.Pejova[60]2AgSe(111)2AgSe[43,54]()[57-59][60][55-56]α1.2.3.22AgSeδ+Schnyders[29]435101.210δ−−−××2TAgeδ+8Manoharan[61]2AgSe2AgSeδ+[35-36]2AgSe()1997R.Xu[20]δ=0.010.33molA.Husmann[30]JingshiHu[62]G.Beck[31-34]2AgSeδmaxδmax2AgSeδ+δmax2SeAgδα+−610δ−∆=δmax527.910110δ−−×≤×2SeAgδ+900527.910110δ−−×≤×2SeAgδ+91.3(2AgSe)α(2AgSeδ+)1(2geAS)2Se(eg2SAδ)X(XRD)(FSEM)3(2ge0ASδδ≥)1022.12AgSe[43,54]αβ[55-56]ααα(2geAS)(eg2SAδ)112.22.2.199.98%99.99%96%SartoriousBP221S0.0001g800B78-1DZF-602010200C−oKSY-12-162.2.2Ag2Se0.5gSe30ml1.25gAgNO3702AgSe[55,63](1)[Ag(NH2CH2CH2NH2)2]+[64]Ag++2NH2CH2CH2NH2=[Ag(NH2CH2CH2NH2)2]+(2)SeSe2-Sex+NH2CH2CH2NH2=(NH2CH2CH2NH2)Sex-1+H2Se(3)[Ag(NH2CH2CH2NH2)2]+Se2-Ag2Se122[Ag(NH2CH2CH2NH2)2]++H2Se=Ag2Se+4NH2CH2CH2NH2+2H+2AgSe2AgSe2.2.3Ag2Se()12Mpa53004005002.3X(PHILIPSX'PertPro,CuKα,1.5406,40kV,40mA)(FESEMSirion200)/(DiamondTG/DTA,0.2ug,0.06uV)2.3.1Ag2Se2h4h6h8h10h12h16h24h2.3.1Xα132h4h6h8hα(014)10hXRDαα(002)(013)(004)(014)12hα(032)(131)10hα2AgSe404244464850Intensity(a.u.)2θ(deg)0311222001130231300321310041230142201324h2h6h8h10h12h16h24h2.3.1Ag2SeXRD2.3.1XRD14a/Ǻb/Ǻc/Ǻ/nm2h4.311477.148197.695773.4924h4.321447.056547.743363.5486h4.329307.058087.758203.4448h4.320737.