nature杂志二维硼纳米片的实验法实现

二维硼纳米片的实验法实现二维硼纳米片的制备Feng等人采用外延生长的策略实现了在Ag（111）基底表面生长不同周期排列结构的两种二维硼纳米片。该材料具有良好的化学惰性，不易被氧化，有望在微电子器件中得到应用。Contents010203040506AbstractGrowthof2DboronStructuresof2Dboron.XPSstudyon2Dboron.FormationmechanismConclusionsAbstract•Avarietyoftwo-dimensionalmaterialshavebeenreportedinrecentyears,yetsingle-elementsystemssuchasgrapheneandblackphosphorushaveremainedrare.•Boronanalogueshavebeenpredicted,asboronatomspossessashortcovalentradiusandtheflexibilitytoadoptsp2hybridization,featuresthatfavourtheformationoftwo-dimensionalallotropes,andoneexampleofsuchaborophenematerialhasbeenreportedrecently.•Here,wepresentaparallelexperimentalworkshowingthattwo-dimensionalboronsheetscanbegrownepitaxiallyonaAg(111)substrate.Twotypesofboronsheet,aβ12sheetandaχ3sheet,bothexhibitingatriangularlatticebutwithdifferentarrangementsofperiodicholes,areobservedbyscanningtunnellingmicroscopy.•Densityfunctionaltheorysimulationsagreewellwithexperiments,andindicatethatbothsheetsareplanarwithoutobviousverticalundulations.•Theboronsheetsarequiteinerttooxidizationandinteractonlyweaklywiththeirsubstrate.•Weenvisagethatsuchboronsheetsmayfindapplicationsinelectronicdevicesinthefuture.Densityfunctionaltheory：密度泛函理论：电子结构理论的经典方法，特别是Hartree-Fock方法和后Hartree-Fock方法，是基于复杂的多电子波函数的。密度泛函理论的主要目标就是用电子密度取代波函数做为研究的基本量。因为多电子波函数有3N个变量（N为电子数，每个电子包含三个空间变量），而电子密度仅是三个变量的函数，无论在概念上还是实际上都更方便处理。B12icosahedralcagesVSgraphitebulkformboronclustersVScarbonclustersvariouscagestructuresB12—，B13+，B19—，B36planarorquasi-planar我是图一.Boronhasthesameshortcovalentradiusandtheflexibilitytoadoptsp2hybridizationascarbon,whichwouldfavourtheformationofvariouslow-dimensionalallotropes.boronnanotubes,fullerenesand2Dboronsheets13–15particularlyinteresting1.The2Dboronstructurehasbeenpredictedtobemetallic16–20,despitebulkboronbeingasemiconductor.2.Some2DboronstructureshaverecentlybeenpredictedtohostDiracfermions22Diracfermions•无质量的狄拉克费米子•就是满足狄拉克方程的费米子。•特性有:速度接近光速，质量为0，表现为良好的导电特性，电子运动受拓扑学保护。应用上石墨烯、拓扑绝缘体表面态的电子都具有这种性质。TheoreticalpredictionVSexperimentalrealization•2Dboronstructures•suchasαsheets16,17,βsheets16,17andχsheets19,20,namedaftertheconnectivityoftheboron.2DboronsheetscanformonmetalsubstratessuchasCu(111)23,Ag(111)andAu(111)24duetothestabilizationofsp2hybridizationbymetalpassivationGrowthof2DboronFigure1|Formationof2DboronsheetsonAg(111).a,STMtopographicimageofboronstructuresonAg(111),withasubstratetemperatureof∼570Kb,Three-dimensionalversionofa,inwhichthestripeswith1.5nmintervalsareclearlyresolved.c,High-resolutionSTMimageofS1phases.TheS1unitcellismarkedbyablackrectangle,andthe1.5nmstripesareindicatedbysolidlines.Growthof2Dborond,STMimageofboronsheetsafterannealingthesurfaceinato650K.Thetwodifferentphasesarelabelled‘S1’and‘S2’.MostboronislandsaretransformedtotheS2phase,buttheS1phasestillremainsinsmallpartsoftheislands.e,STMimageobtainedontheareamarkedbytheblackrectangleind.f,High-resolutionSTMimageoftheS2phase,zoomedfrome.Notethattheorientationoftheimageisrotatedtoallowcomparisonwithc.BiasvoltagesofSTMimages:−4.0V(a,b),0.9V(c),−4.0V(d),1.0V(e,f).图注：•1a、monolayer(ML)islandswithaperfectlyorderedstructure•1b、parallelstripes•1c、ordered,parallelrowsofprotrusions，horizontaldirection•1d、S2phasecoexistswiththeS1phasefrom650to800K•beobtainedbydirectlygrowingborononAg(111)withasubstratetemperatureof∼680K•1e/f:Anotherobviousfeatureisthattheprotrusionsalongtherowsaredividedintosectionswithalternatebrighteranddarkerprotrusions.Eachsectioncomprisesfiveprotrusions,sotheperiodicityalongtherowis3.0Å×5=1.5nm.biasvoltages：•偏置电压是指晶体管放大电路中使晶体管处于放大状态时，基极-射极之间、集电极-基极之间应该设置的电压。Theβ12sheetwasplacedonAg(111)withtheboronrowsinthe[-112]directionoftheAg(111)surface,asshowninFig.2a.a,b,TopandsideviewsoftheS1modelc,SimulatedSTMtopographicimageoftheβ12sheet.Structuresof2Dboron.d,e,TopandsideviewsoftheS2model,whichcorrespondstoaχ3sheetof2DborononAg(111).f,SimulatedSTMtopographicimageoftheχ3sheet.Modelsoftheβ12andχ3sheetsaresuperimposedontheirsimulatedSTMimages,whichagreeverywellwiththeexperiments.ThestripedpatternofS1andthealternatingbright–darkprotrusionsofS2arebothreproducedwell.Structuresof2Dboron.first-principlescalculations•根据原子核和电子互相作用的原理及其基本运动规律，运用量子力学原理，从具体要求出发，经过一些近似处理后直接求解薛定谔方程的算法，习惯上称为第一性原理。•第一性原理通常是跟计算联系在一起的，是指在进行计算的时候除了告诉程序你所使用的原子和他们的位置外，没有其它的实验的，经验的或者半经验的参量，且具有很好的移植性。作为评价事物的依据，第一性原理和经验参数是两个极端。第一性原理是某些硬性规定或推演得出的结论，而经验参数则是通过大量实例得出的规律性的数据，这些数据可以来自第一性原理(称为理论统计数据)，也可以来自实验(称为实验统计数据)。latticemismatch•当在某种单晶衬底上生长另一种物质的单晶层时,由于这两种物质的晶格常数不同,会在生长界面附近产生应力,进而产生晶体缺陷--失配位错.通常把这种由于衬底和外延层的晶格常数不同而产生的失配现象叫晶格失配。Moirépattern•莫尔条纹是18世纪法国研究人员莫尔先生首先发现的一种光学现象。从技术角度上讲，莫尔条纹是两条线或两个物体之间以恒定的角度和频率发生干涉的视觉结果，当人眼无法分辨这两条线或两个物体时，只能看到干涉的花纹，这种光学现象中的花纹就是莫尔条纹。Reasonfor2differentphases•wecalculatedtheatomicchargesofthesetwophasesbasedontheBaderanalysis(SupplementaryFig.2).InhomogeneouschargedistributionisfoundalongtheboronrowsinbothS1andS2phases.•SuchchargeinhomogeneitycomesfromthecommensurationbetweentheboronlatticesandtheAg(111)lattice,whichresultsindifferentlocationsoftheboronatomsontheAg(111)lattice,especiallyalongtheboronrowdirection.Measuringthea