简介:WehavestudiedtheinterfacialstructuresofAlN/Si(111)grownbymetal-organicchemicalvapourdeposition.X-rayphotoelectronspectroscopyandAngerelectronspectroscopywereusedtoanalysethecomponentsandchemicalstructuresofAlN/Si(111).Theresultsindicatedthatamix-crystaltransitionregion,approximately12nm,waspresentbetweentheAlNfilmandtheSisubstrateanditwascomposedofAlNandSi3N4.AfteranalysiswefoundthattheexistenceofSi3N4couldnotbeavoidedintheAlN/Si(111)interfacebecauseofstrongdiffusionat1070℃.EveninAlNlayerSi-Nbonds,Si-Sibondscanbefound.
简介:TheadsorptionofCOonPtgroupmetals,asamostfundamentalelementaryreactionstep,hasbeenwidelystudiedincatalysisandelectrocatalysis.Particularly,thestructuresofCOonPt(111)havebeenextensivelyinvestigated,owingtoitsimportancetobothfundamentalandappliedcatalysis.Yet,muchlessisknownregardingCOadsorptiononaPt(111)surfacemodulatedbysupportedoxidenanostructures,whichisofmorerelevancetotechnicalcatalysis.Wethusinvestigatedthecoverage-dependentadsorptionofCOonaPt(111)surfacepartiallycoveredbyFeOxnanostructures,whichhasbeendemonstratedasaremarkablecatalystforlow-temperatureCOoxidation.Wefoundthat,duetoitsstrongchemisorption,thecoverage-dependentstructureofCOonbarePtisnotinfluencedbythepresenceofFeOx.But,oxygen-terminatedFeOxnanostructurescouldmodulatethediffusivityofCOattheirvicinity,andthusaffecttheformationoforderedCOsuperstructuresatlowtemperatures.Usingscanningtunnelingmicroscopy(STM),weinspectedthediffusivityofCO,followedthephasetransitionsofCOdomains,andresolvedthemoleculardetailsofthecoverage-dependentCOstructures.OurresultsprovideafullpictureforCOadsorptiononaPt(111)surfacemodulatedbyoxidenanostructuresandshedlightsontheinter-adsorbateinteractiononmetalsurfaces.
简介:TostudytheadsorptionbehaviorofCu+inaqueoussolutiononsemiconductorsurface,theinteractionsofCu+andhydratedCu+cationswiththecleanSi(111)surfacewereinvestigatedviahybriddensityfunctionaltheory(B3LYP)andMller-Plessetsecond-orderperturbation(MP2)method.ThecleanSi(111)surfacewasdescribedwithclustermodels(Si14H17,Si16H20andSi22H21)andafour-siliconlayerslabunderperiodicboundaryconditions.CalculationresultsindicatethatthebondingnatureofadsorptionofCu+onSisurfacecanbeviewedaspartialcova-lentaswellasionicbonding.ThebindingenergiesbetweenhydratedCu+cationsandSi(111)surfacearelarge,suggestingastronginteractionbetweenthem.ThecoordinationnumberofCu+(H2O)nonSi(111)surfacewasfoundtobe4.Asthenumberofwatermoleculesislargerthan5,watermoleculesformahydrogenbondnetwork.Inaqueoussolution,Cu+cationswillsafelyattachtothecleanSi(111)surface.
简介:TheroleoftemperatureontheoxidationdynamicsofCu2OonZnO(0001)wasinvestigatedduringtheoxidationofCu(111)/ZnO(0001)byusingoxygenplasmaastheoxidant.AtransitionfromsinglecrystallineCu2O(111)orientationtomicro-zonephaseseparationwithmultipleorientationswasrevealedwhentheoxidationtemperatureincreasedabove300°C.TheexperimentalresultsclearlyshowtheeffectoftheoxidationtemperaturewiththeassistanceofoxygenplasmaonchangingthemorphologyofCu(111)filmandenhancingthelateralnucleationandmigrationabilitiesofcuprousoxides.Averticaltop-downoxidationmodeandalateralmigrationmodelwereproposedtoexplainthedifferentnucleationandgrowthdynamicsofthetemperature-dependentoxidationprocessintheoxidationofCu(111)/ZnO(0001).
简介:Usingfirst-principlescalculations,wesystematicallystudythedissociationsofO2moleculesondifferentultrathinPb(111)films.AccordingtoourpreviousworkrevealingthemolecularadsorptionprecursorstatesforO2,wefurtherexplorewhytherearetwonearlydegenerateadsorptionstatesonPb(111)ultrathinfilms,butnoprecursoradsorptionstatesexistingatallonMg(0001)andAl(111)surfaces.Thereasonisconcludedtobethedifferentsurfaceelectronicstructures.FortheO2dissociation,weconsiderboththereactionchannelsfromgas-likeandmolecularlyadsorbedO2molecules.WefindthattheenergybarrierforO2dissociationfromthemolecularadsorptionprecursorstatesisalwayssmallerthanthatfromO2gas.ThemostenergeticallyfavorabledissociationprocessisfoundtobethesameondifferentPb(111)films,andtheenergybarriersarefoundtobeinfluencedbythequantumsizeeffectsofPb(111)films.
简介:WepresentthetemperaturedependentelectricaltransportmeasurementsofAg/Si(111)-(√3×√3)R30°bytheinsitumicro-four-pointprobemethodintegratedwithscanningtunnelingmicroscopy.Thesurfacestructurecharacterizationsshowhexagonalpatternsatroomtemperature,whichsupportstheinequivalenttriangle(IET)model.Ametal-insulatortransitionoccursat-115K.Thelowtemperaturetransportmeasurementsclearlyrevealthestronglocalizationcharacteristicsoftheinsulatingphase.