第4章-表面分析手段1-SEM

第四章——表面分析手段

李硕琦山东科技大学材料学院2015.4ComplexityofRealSurfaces(复杂性)是英雄还是装备？这不是一个问题！BEAConfidential.|3选择学校的另一个标准-分析测试中心BEAConfidential.|4选择学校的另一个标准-分析测试中心BEAConfidential.|5选择学校的另一个标准-分析测试中心BEAConfidential.|6BEAConfidential.|7选择学校的另一个标准-分析测试中心选择学校的另一个标准-分析测试中心BEAConfidential.|8BEAConfidential.|9BEAConfidential.|10表面分析的两个方面

SurfaceSensitivityandSpecificityTwomajordifficultieswithsurfacesciencestudies:(a)Absolutenumberofatomsinsurfaceissmall(sensitivity灵敏度)Typicalsinglecrystalsurfaceof1cm2areacontains~1015atoms/10-9moles表面原子的绝对数量是比较小的。典型单晶1cm2的面积上，只有1015或者说10-9

个原子SurfaceSensitivityandSpecificityTwomajordifficultieswithsurfacesciencestudies:(b)Ratioofsurfaceatomstobulkatomsissmall(specificity特异性)Typicalsurface:bulkatomratioinsolid~10-7-10-8.dependingonsurfacestructureneedtobeabletoseparatesurfacesignalfrombulksignal.表面原子百分比和本体原子的比例很小。所以需要讲表面原子的信号和本体信号区分开来。SurfaceSciencemethodsExperimentalsurfacescienceComputationalsurfacescienceConstructionofmodelsAB+C=>AC+BMethodsforsurfaceanalysisTwomajorinstrumentationtechniquesforsurfaceanalysis:Surfacemicroscopy(表面形貌):a)imagingthesurfaceanddeterminingthemorphology,atomiccrystallinestructure,andotherphysicalpropertiesandfeaturesatdifferentsizescale(nanometerstomicrometers);在纳米到微米的尺度上对表面进行拍照，测定其形貌、晶体结构和其它物理性质。（二维）b)3-dimensionalsurfacestructurewithhighresolution.高分辨率的三维表面结构MethodsforsurfaceanalysisTwomajorinstrumentationtechniquesforsurfaceanalysis:2.Surfacespectroscopy(表面光谱):a)identifyingthesurfacechemicalspeciesanddeterminingtheconcentrations分辨表面化学组成，确定其浓度b)providingbothqualitativeandquantitative(lessused)informationaboutthecompositionofsurfacelayer提供表面层组成的定性定量信息。(afewtoafewtensofÅdepth).SurfaceAnalyticalTechniquesModernsurfaceanalyticaltechniquesarecharacterizedbyabeams（束）in/beamsoutorprobe（探针）measureapproach.SurfaceAnalyticalTechniquesIncidentbeam/probeinteractswithsurfacelayer,whileoutputbeamcarryingthemeasuredsurfaceinformationisanalyzed.起始的“束”或者探针和表面层发生相互作用，而表面释放的“束”携带表面的信息以供分析。Electric(magnetic)field电场SurfaceElectrons电子Heat热Ions离子Photons光子Neutrals中性物质那些“beam”可供使用？4.1Scanningelectronmicroscopy

扫描电子显微镜Scanningelectronmicroscopes(SEMs),inventedinthe1930s,letusseeobjectsassmallas10nanometers4.2Scanningelectronmicroscopy

NoblePrize!Itisamicroscopethatproducesanimagebyusinganelectronbeamthatscansthesurfaceofaspecimeninsideavacuumchamber.SEM是用在真空腔中用电子束扫描样品表面，从而得到图像的显微镜。4.1ScanningelectronmicroscopyWhatisSEM?WhatcanwestudyinaSEM?我们从SEM可以得到什么？Morphology形貌Chemistry化学成分4.1ScanningelectronmicroscopyWhatisSEM?4.1ScanningelectronmicroscopyWhatdoesitlookslike….AFMCantileverTipAntHeadBloodCellsDiamondThinFilm(NumerousMultifacetedMicro-crystals)Microstructureofaplaincarbonsteelthatcontains0.44wt%ofcarbonCalciumPhosphateCrystal4.1Scanningelectronmicroscopy作用原理-光电效应Thescanningelectronmicroscope(SEM)usesafocusedbeamofhigh-energyelectronstogenerateavarietyofsignalsatthesurfaceofsolidspecimens.SEM用聚焦高能电子束来在样品表面产生各种信号。4.1ScanningelectronmicroscopyThesignalsthatderivefromelectron-sampleinteractionsrevealinformationaboutthesampleincludingexternalmorphology(texture),chemicalcomposition,andcrystallinestructureandorientationofmaterialsmakingupthesample.通过电子-样品相互作用释放关于样品形貌、化学组成、晶体结构等信息。4.1Scanningelectronmicroscopy4.1Scanningelectronmicroscopy

Wheredoesthesignalscomefrom?

Diameteroftheinteractionvolumeislargerthantheelectronspot.电子轰击点的面积比其作用体积的直径小。4.1ScanningelectronmicroscopySignalsfromthesampleIncomingelectrons入射电子Secondaryelectrons二次电子Backscatteredelectrons背散射电子Augerelectrons俄歇电子X-raysCathodo-luminescence(light)阴极荧光Sample4.1Scanningelectronmicroscopy

Secondaryelectrons(SE)二次电子

GeneratedfromthecollisionbetweentheincomingelectronsandthelooselybondedouterelectronsLowenergyelectrons(~10-50eV)OnlySEgeneratedclosetosurfaceescape(topographic(地形上的)informationisobtained)

只有表面才逸出二次电子NumberofSEisgreaterthanthenumberofincomingelectrons。二次电子数量比入射电子数目多。4.1Scanningelectronmicroscopy

Backscatteredelectrons(BSE)背散射电子

Afractionoftheincidentelectronsisretarded(阻止)bytheelectro-magneticfieldofthenucleusandifthescatteringangleisgreaterthan180°theelectroncanescapefromthesurfaceHighenergyelectrons(elasticscattering)弹性碰撞，能量高。FewerBSEthanSE

背散射电子比二次电子少4.1Scanningelectronmicroscopy

BSEvsSE

SEproduceshigherresolutionimagesthanBSE二次电子提供更高分辨率Byplacingthesecondaryelectrondetectorinsidethelens,mainlySEaredetectedResolutionof1–2nmispossibleBEAConfidential.|32二次电子背散射电子4.1Scanningelectronmicroscopy

X-rays

Photonsnotelectrons

光子而非电子EachelementhasafingerprintX-raysignal

每种元素都有X光信号指纹。（元素定性定量分析）PoorerspatialresolutionthanBSEandSE分辨率差4.1Scanningelectronmicroscopy

X-rays

RelativelyfewX-raysignalsareemittedandthedetectorisinefficientX射线信号相对较少relativelylongsignalcollectingtimesareneeded

采集时间长4.1Scanningelectronmicroscopy

X-rays

Mostcommonspectrometer:EDS(energy-dispersivespectrometer)最常用光谱仪EDSSignaloverlapcanbeaproblem信号重叠Fig.2EDSgraphicofuncoatedAZ91magnesiumalloy.HikmetAltun,HakanSiniciCorrosionbehaviourofmagnesiumalloyscoatedwithTiNbycathodicarcdepositioninNaClandNa2SO4solutionsMaterialsCharacterization,Volume59,Issue3,2008,266-270/10.1016/j.matchar.2007.01.004Fig.3EDSgraphicofTiNcoatedAZ91magnesiumalloy.HikmetAltun,HakanSiniciCorrosionbehaviourofmagnesiumalloyscoatedwithTiNbycathodicarcdepositioninNaClandNa2SO4solutionsMaterialsCharacterization,Volume59,Issue3,2008,266-270/10.1016/j.matchar.2007.01.0044.1Scanningelectronmicroscopy

X-rays

Wecananalyzeoursampleindifferentmodes模式多chemicalconcentrationmap(elementalmapping)spotanalysislinescanFig.

8FESEMimageandEDXspectrumofRh/ZrO2filmspreparedataRh/Zrsourcemolarratioof0.05(depositiontemperatureof1180K).AnarrowindicatesoneofRhnanoparticle.二氧化锆的薄膜AkihiroHonda,TeiichiKimura,AkihikoIto,TakahiGotoRh-nanoparticle-dispersedZrO2filmspreparedbylaserchemicalvapordepositionSurfaceandCoatingsTechnology,Volume206,Issues11–12,2012,3006-3010/10.1016/j.surfcoat.2011.12.038spotanalysis点扫描Fig.5(A)SEMimageofexternalsurfaceoftheCo/SiO2-Z-Sp-Pd;(B)cross-sectionSEMimageoftheCo/SiO2-Z-Sp-PdwiththeintensityofPd,SiandAlX-raysignalsfromtheEDSlinescan;(C)externalsurfaceEDSanalysisresultoftheCo/SiO2-Z-Sp...二氧化硅薄膜YuzhouJin,RuiqinYang,YasuhiroMori,JianSun,AkiraTaguchi,YoshiharuYoneyama,TakayukiAbe,Noritat...PreparationandperformanceofCobasedcapsulecatalystwiththezeoliteshellsputteredbyPdfordirectisoparaffinsynthesisfromsyngasAppliedCatalysisA:General,Volume456,2013,75-81/10.1016/j.apcata.2013.02.014linescan线扫描Fig.1SectionoftheCa–Mg–Znphasediagram,accordingtoRef.<ce:cross-refrefid="b0215">[43]</ce:cross-ref>.CompositionsreportedbySenkovandScott<ce:cross-refrefid="b0010">[2]</ce:cross-ref>aremarkedbybluecircles,andthenewhighzinc...

Ca–Mg–Zn金属玻璃的腐蚀J.D.Cao,N.T.Kirkland,K.J.Laws,N.Birbilis,M.FerryCa–Mg–ZnbulkmetallicglassesasbioresorbablemetalsActaBiomaterialia,Volume8,Issue6,2012,2375-2383/10.1016/j.actbio.2012.03.009mapping4.1Scanningelectronmicroscopy

Summary

Signals:Secondaryelectrons(SE):mainlytopographyLowenergyelectrons,highresolution高分辨率Surfacesignald