材料表面与界面(1)分析

材料的表面与界面SurfacesandInterfacesinMaterials任课教师：耿林教授哈尔滨工业大学材料科学与工程学院第1章前言主要参考文献：(1)李恒德，肖纪美，材料表面与界面，清华大学出版社。(2)叶恒强，材料界面结构与特性,科学出版社,1999。(3)胡福增，陈国荣，杜永娟，材料表界面，华东理工大学出版社，2007。(4)JamesM.Howe,InterfacesinMaterials,AWiley-intersciencePublication,1997.(5)HansLuth,SurfacesandInterfacesofSolidMaterials,Springer,1995.(6)D.WolfandS.Yip,MaterialsInterfaces,Chapman&Hall,1992.固态界面的定义:Asolidinterfaceisdefinedasasmallnumberofatomiclayersthatseparatetwosolidsinintimatecontactwithoneanother,wherethepropertiesdiffersignificantlyformthoseofthebulkmaterialsitseparates.1.1序固态界面的特点:●Someofthemostimportantpropertiesofmaterialsinhigh-technologyapplicationsarestronglyinfluencedorevencontrolledbythepresenceofsolidinterfaces.●Itiswidelyappreciatedthatahighlyinterdisciplinaryapproachholdsthegreatestpromiseforprovidingnovelinsightsintothefundamentalphysical,chemical,electronic,andmechanicalprocessesatsolidinterfaces.●Theimportanceofinterfacematerialsisbasedprimarilyontheirinherentinhomogeneity,i.e.thefactthatphysicalpropertiesatornearaninterfacecandifferdramaticallyfromthoseofthenearbybulkmaterial.●Anapproachutilizingthecomplementarycapabilitiesofcomputersimulationandexperimentseemstobeparticularlypromisingintheinvestigationofstructure-propertycorrelations.固态界面的分类:Onecanimaginemanywaysofclassifyinginterfacialsystems,forexample,bydistinguishingcommensuratefromincommensuratesystem,coherentfromincoherentinterfaces,homophase(grainboundary)materialsfromheterophase(dissimilar-material)interfaces,orinternalinterfacesfromthin-film-typesystems.Thelatterdistinctionbetweenburiedinterfacesandsystemscomposedofthin-film-typeinterfacesappearstobeparticularlymeaningfulfortworeasons:first,becauseofthefundamentallydifferentexperimentaltechniquesrequiredfortheirinvestigationandsecond,becausethelatticeparameter(s),andhencethephysicalpropertiesintheinterfacialregion,dependstronglyonwhetherornottheinterfaceisembeddedbetweenbulkmaterial.Fig.1-1Distinctionofthreetypesofinterfacialsystems.Dependingonwhetherthesystemisembeddedinbulkmaterialonbothsidesoftheinterface,ononlyonesideornotatall,wedistinguish“bulk”,“epitaxial”,and“thin-film”interfaces.AandBaregenerallydifferentmaterials.BulkperfectCrystal2BulkperfectCrystal1Interfaceregion2Interfaceregion1InterfaceplaneMaterialBXYZMaterialA固态界面的研究内容:●Relationshipamonginterfaceenergy,interfacestructureandinterfaceproperties.●Formationandstabilityoftheinterfaces:Energyofthesystem,thermodynamicandkineticsoftheinterfaces.固态界面的研究方法:●Theexperimentalproblemsliemainlyintheextremelyhighspatialresolution,coupledwithhighdetectionsensitivity,whicharerequiredtoidentityminuteamountsofchemicalspecies,chargestatesofatomsandpointdefects,anddifferentphaseswhichmaybepresentinthenarrowinterfaceregion.●Becausethepropertiesintheinterfacialregionarecontrolledbyrelativelyfewatoms,electronicandatomic-levelcomputersimulationscanprovideaclose-upviewofthemostcriticalpartofthematerial.Thelocalnatureofatomicbonding,thepositionsandmovementsofatoms,localstresses,etc.,canbeinvestigatedbycomputersimulations.1.2Atomicstructureandinteratomicbonding●Thebindingenergyisdefinedastheenergyneededtotransformonemoleofsolidorliquidintoagasatzerotemperatureandpressure.Itisapproximatelythesamemagnitudeastheenergyofsublimation△Hswhentransformingasolidtoagasortheenergyofvaporization△Hvwhentransformingaliquidtoagas,exceptthattheseareusuallymeasuredat1atmpressure.Thesequantitiesareoftenobtainedatfinitetemperaturessuchas298Korattheboilingpoint,butthisdoesnotalterthebindingenergyorbondenthalpy,whichisassumedtobeindependentoftemperature.Theseenergiesarerelatedtoafundamentalenergyinmaterials,theinteratomicpotentialenergybetweenatoms.1.2.1Interatomicpotentialandbindingenergy1.2.2Interatomicpotentialandbindingenergy126/2/beerrrrr/.FddrIftheatomsaredisplacedtowardoneanother,arepulsiveforceactstoincreasetheinteratomicdistance.Thisrepulsiveforceispositive.Theoppositeoccurswhentheatomsarestretchedapart.Hooke’slawTheminimumpotentialenergycorrespondstotheequilibriuminteratomicseparationre.Insolids,recanreadilybemeasuredbyX-raydiffraction.Thedepthofthewellisclearlyproportionaltothestrengthoftheinter-atomicbond.bLennard-Jonespotential:1.2.2InteratomicpotentialandbindingenergyInmetals,attractiveinteractionbetweenatomsisshort-rangewithanr-6dependence.Hence,thenearest-neighborapproximationworkswellforestimatingthebindingenergyformetals.6rInionicsolids,theattractionbetweenthepositiveandnegativeionsiscoulombicandmuchlongerinrange.Theattractivecoulombicpotentialisproportionaltor-1,whichdecaysslowlywithincreasingr.Therepulsivepotentialmaydisplayanr-12dependence,aswithmetals,sotheresultingprofilelookslikethatshowninFig.1-3Fig.1-3Thebrokencurveshowstheinteratomicpotentialenergywhentheattractiveinteractionislong-rangewithanr-1dependence1.2.2Interatomicpotentialandbindingenergy6r刚性球模型：Clearlytherepulsiveinteractionisveryshort-range,whereastheattractiveinteractionissomewhatlonger.Thisstrongrepulsiveinteractionmakesitoftenrealistictorepresentatomsas“hardspheres”.最近邻假设：Wh