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Electronic structures of the F-terminated AlN nanoribbons

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PRAMANAc󰁭IndianAcademyofSciencesVol.78,No.3

—journalofMarch2012

physicspp.469–474ElectronicstructuresoftheF-terminatedAlNnanoribbons

YU-LINGSONG1,2,∗,DAO-BANGLU2,BEN-LIANGCUI2andJIAN-MINZHANG11CollegeofPhysicsandInformationTechnology,ShaanXiNormalUniversity,Xian,

ShaanXi710062,China2CollegeofPhysicsandElectronicEngineering,NanyangNormalUniversity,

Nanyang473061,China∗Correspondingauthor.E-mail:dblu985@163.com

MSreceived1May2011;accepted14October2011

Abstract.Usingthefirst-principlescalculations,electronicpropertiesfortheF-terminatedAlN

nanoribbonswithbothzigzagandarmchairedgesarestudied.Theresultsshowthatboththezigzag

andarmchairAlNnanoribbonsaresemiconductingandnonmagnetic,andtheindirectbandgapof

thezigzagAlNnanoribbonsandthedirectbandgapofthearmchaironesdecreasemonotonically

withincreasingribbonwidth.Incontrast,theF-terminatedAlNnanoribbonshavenarrowerband

gapsthanthoseoftheH-terminatedoneswhentheribbonshavethesamebandwidth.Thedensity-

of-states(DOS)andlocaldensity-of-states(LDOS)analysesshowthatthetopofthevalenceband

fortheF-terminatedribbonsismainlycontributedbyNatoms,whileatthesideoftheconduc-

tionband,thetotalDOSismainlycontributedbyAlatoms.Thechargedensitycontouranalyses

showthatAl–FbondisionicbecausetheelectronegativityofFatomismuchstrongerforFatom

thanforAlatom,whileN–Fbondiscovalentbecauseofthecombinedactionofthestronger

electronegativityandthesmallercovalentradius.

Keywords.Firstprinciple;electronicproperty;bandstructure;F-terminated;AlNnanoribbon.

PACSNo.73.21.−b

1.Introduction

Electronicandmagneticpropertiesofsingle-layergraphenehaveattractedmuchatten-

tion[1–6].Thesingle-layeredIII–Vsemiconductors,especiallythegroupIIInitrides,

havebeenwidelyusedinelectronicdevicesbecauseoftheirhighthermalstabilityand

theirpotentialtechnologicalapplications[7–9].Nanoribbonshaveattractedincreasing

attentionbecauseoftheirnovelgeometriesaswellasthepromisingpropertiesrelating

to,e.g.,opticsandnanoscaleelectronicdevices.AsanimportantmemberofgroupIII

nitrides,AlNisthelargestband-gapsemiconductor,whichisperfectfortheepitaxial

growthoftheGaN-basedheterostructuresduetoitssmalllatticemismatchwithGaN

anditssuperiorpropertiessuchashighthermostabilityandconductivityandreliable

DOI:10.1007/s12043-011-0240-y;ePublication:5March2012469Yu-LingSongetaldielectricproperties.Henceiswidelyusedinelectronicindustry.Duetothelargeion-

icityoftheAl–Nbond,AlNnanoribbons(AlNNRs)possessnovelpropertieswhichare

differentfromgraphenenanoribbonsleadingtonewpotentialapplicationsinopticsand

nanoscaleelectronicdevices.TheperfectandwithAlorNvacantAlNNRswithHtermi-

nationhavebeenintensivelystudiedusingfirstprinciplescalculationsandobtainedsome

usefulresults[9].However,sometheoreticalstudiesshowthattheelectronicproperties

ofthenanomaterialscanbemodulatedbytheterminatedFatom[10–12].Uptonow,

therearenoreportsabouttheelectronicpropertiesofF-terminatedAlNNRs.

Inthispaper,AlNNRwithzigzagedge(ZAlNNR)andarmchairedge(AAlNNR)

terminatedwithFatomshavebeeninvestigatedbyusingthefirst-principlesprojector-

augmentedwave(PAW)potentialwithinthedensityfunctiontheory(DFT)framework

underthegeneralizedgradientapproximation(GGA).Therestofthepaperisorganized

asfollows.ThecalculationmethodandmodelsofthetwotypesofF-terminatedAlNNRs

aregivenin§2.Theenergybandstructures,thedensity-of-states(DOS)andthecharge

densityofthesystemsareanalysedin§3andconclusionsarepresentedin§4.

2.Calculationmethodandstructuremodel

ThecalculationsareperformedusingtheVASPbasedonDFT[13–18].Theelectron-ion

coreinteractionisrepresentedbythePAWpotentials[19].Totreatelectronexchangeand

correlation,wechosethePerdew–Burke–Ernzerhof(PBE)formulationoftheGGA[20],

whichyieldscorrectground-statestructureofthecombinedsystems.Thecut-offenergy

fortheplanewavesischosentobe450eV.The2s22p3,3s23p1and2s22p5electronsare

takenasthevalenceelectronsforN,AlandFatoms,respectively.Inordertosimulate

infinitelongisolatednanoribbon,weuseasupercellgeometrywhereeachplaneissep-

aratedfromitsreplicaby15Åinbothedge-to-edgeandlayer-to-layerdirections.The

sampledkpointsintheBrillouinzonearegeneratedbytheMonkhorst–Packscheme[21]

with󰀐-centredgrids.Toavoidnumericalinstabilityduetolevelcrossingandquasidegen-

eracyneartheFermilevel,weuseamethodofMethfessel–Paxtonfirst-ordersmearing

withawidthof0.2eV.GeometricstructuresoftheAlNNRsarefullyrelaxedtominimize

thetotalenergyofthesystemuntilaprecisionof10−4isreached.Theconjugategradient

minimizationisusedfortheoptimizationofatomcoordinatesuntiltheforcesactingon

eachatomaresmallerthan0.02eV/Å.

N

Al

F

(a)(b)

Figure1.Geometryfor(a)F-terminated6-ZAlNNRand(b)F-terminated7-

AAlNNR.

470Pramana–J.Phys.,Vol.78,No.3,March2012

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纤锌矿纳米CuInS2高压下晶体结构及物性研究

纤锌矿纳米CuInS2高压下晶体结构及物性研究

I

中文摘要

纤锌矿纳米CuInS

2高压下晶体结构及物性研究

论文作者：叶梅艳

指导教师：朱品文 教授

专业名称：凝聚态物理

AⅠ

-BⅢ

-CⅥ

2系列化合物中，CuInS

2半导体材料因为具有可调谐吸收带隙

（1.1-1.5 eV）、较高的吸收系数、光致发光和强烈局域表面等离子振荡等优异

性质，在光伏电池、LED、生物大分子荧光标记和非线性光学器件等领域具有巨

大的应用潜质而备受关注。CuInS

2化合物在自然界中以黄铜矿结构存在，在高温

下可以获得闪锌矿和纤锌矿两种亚稳相结构，降温后又回到黄铜矿结构。除了化

学方法以外，高压可以改变原子间距和电子结构，调节物质的物理化学性质，获

得其他手段不能获得的新结构、新现象和新性质。在压力作用下，黄铜矿CuInS

2

展示丰富的结构相变，并发现压力可以有效调控其光学、电学等性质。近几年发

现纤锌矿纳米CuInS

2亚稳相可以稳定存在于常温常压下，但其高压下结构稳定

性以及压力调控的物理化学性质仍不清楚。

本论文首先通过热注入法成功制备亚稳相纳米尺寸纤锌矿CuInS

2（P

6

3mc

），

利用金刚石对顶压砧（DAC）装置，将高压技术与同步辐射X光衍射、吸收光谱、

直流电阻率和光电流测试相结合，系统研究其高压下结构稳定性以及压力调控下

样品光学性质、电学性质和光电性质的变化，得到以下研究结果：

1. 利用热注入法成功制备了亚稳相纳米纤锌矿CuInS

2，XRD图谱精修拟合

确定其为六方相结构，空间群为P

6

3mc

；通过谢乐公式得到其晶粒大小约

为20 nm。TEM测试结果显示样品形貌为六方形薄片，结晶性较好。EDS

测试结果显示元素比例为27.42%、24.64%和47.94%。XPS测试结果显示

元素比例为28.90%、23.96%和47.14%，与EDS测试结果几乎相一致。

2. 原位高压同步辐射X光衍射结果显示：10.3 GPa处发生无序相纤锌矿

CuInS

2（P

6

3mc

）向无序相岩盐矿CuInS

BiS3-ppy -main

BiS3-ppy -main

ContentslistsavailableatScienceDirectNanoEnergyjournalhomepage:/locate/nanoenFullpaperBio-inspiredengineeringofBi2S3-PPyyolk-shellcompositeforhighlydurablelithiumandsodiumstorageHaichenLiang,JiangfengNi⁎,LiangLi⁎CollegeofPhysics,OptoelectronicsandEnergy,CollaborativeInnovationCenterofSuzhouNanoScienceandTechnology,CenterforEnergyConversionMaterials&Physics(CECMP),SoochowUniversity,Suzhou215006,PRChinaARTICLEINFOKeywords:BismuthsulfideYolk-shellLithiumstorageSodiumstorageABSTRACTBismuthbasedcompoundsareuniquelyinterestingasanodematerialsinenergystoragedevicessuchasrechargeablebatteries,owingtotheirlargevolumetriccapacityandsuitableoperatingpotentialhigherthangraphite.Howtoachievethehighcapacitydurablyandrobustlyremainsanopenchallenge.Toaddressthisissue,hereweproposeabio-inspiredmaterialengineeringofyolk-shellcompositethatconsistsofbismuthsulfide(Bi2S3)nanowireassemblyintimatelyencapsulatedinpolypyrrole(PPy)shell.TheBi2S3yolkfeaturesalargevoidspaceandashortdiffusiondistance,whilethePPyshellishighlyconductive,flexibleandresilient,allowingforthefreevolumevariationuponionuptakeandrelease.Whenusedasanode,theBi2S3-PPyyolk-shellcompositeexhibitsasuperiorListoragecyclability(99%for500cycles)andahighratecapability(337mAhg–1at10C),outstrippinganypreviousbismuthbasedmaterials.Thiscompositealsoaffordsahighreversiblecapacityof591mAhg−1andafavorabledurabilityforNastorage.ThediscrepancybetweenLiandNastoragemaycorrelatetothelargervolumechangeofBialloyingwithNa(∼250%)againstwithLi(~110%).Thisworkoffersapotentialcreativeapproachtoengineeringefficientelectrodesforenergystorageapplications.1.IntroductionRechargeablebatterytechnologiesplayavitalroleinoureverydaylifeandvariousfieldsofsociety,forexample,electricvehiclepropul-sionandstationaryenergystorage[1,2].Theimplementationoflithium-ionbatteries(LIBs)onalargescalefacesincreasingconcernontheavailabilityandcostoflithium.Onemostappealingalternativeistousesodium,whichexhibitsarichintercalationchemistryandpossessesaresourceinprincipleunlimitedontheearth[3,4].Inaddition,roomtemperaturesodium-ionbatteries(SIBs)aremuchcheaperthanLIBsandtherefore,promisingforlarge-scaleenergystorage.Currently,onekeychallengeforbothtechnologiesistofindsuitableanodeswithlargecapacityandnotabledurabilityatrationalrechargerates[5].WhilegraphiteisthedominantLianode,itdoesnothostahighconcentrationofNa+ionsatroomtemperature.Somemetals(Sn,Sb,Bi,etc.)andtheircompoundscouldpromisegreatercapacityandbetterdurabilityforbothlithiumandsodiumstorage,owingtotheirhighvolumetriccapacityandsuitableworkingpotentialthateliminatespossiblemetalplating[6–8].Bismuthsulfide(Bi2S3),alowbandgap(~1.3eV)semiconductorwithalaminarstructureandhighabsorptioncoefficient,hasemergedasanattractivematerialforphotovoltaics,photodetector,andthermo-electric[9–11].Recently,Bi2S3nanomaterialssuchasnanorods,nanowires,andnanotubeshavebeenshowntobeelectrochemicallyactiveforLiandNastorage[12,13].Inparticular,theircomplexassembliespromiseenhancedactivityforrechargeablebatteriesduetohighsurfaceareaanduniquearchitecture[14,15].Theoretically,Bi2S3iscapableofaffordingaspecificcapacityof625mAhg−1,orvolumetriccapacityof4250mAhcm−3,whichismuchhigherthanthatofgraphite.However,suchahighcapacityisoftencompromiseduponcycling,duetoelectrodepulverizationandlossofelectronicconnectioncausedbyhugevolumetricexpansionuponLiorNainsertion.Tomitigatethisdifficulty,ourgroupandothersattemptedtointegrateBi2S3materialintonanocarbonssuchasreducedgrapheneoxideandcarbonnanotube[16–19].FunctionalgroupsofthenanocarbonscantightlyholdBi2S3nanoparticlesontheconductivenetwork,thuslargelyavoidingthefailureofelectronicconnection[20].Nonetheless,asnanocarboncannotfullywrapactiveparticles,thedissolutionofpolysulfideintermediatesSx2−(x≥2)intoelectrolyteisinevitable,whichisrecognizedasanothermajorcontributionofcapacitydecay.Consequently,long-termstabilityofBi2S3materialshasnotbeenachievedtodate.Furtherimprovementinthecyclabilityisextremelyimportantanddesirableforbatteryapplication.ConcurrentwiththeadvancesofBi2S3nanomaterials,yolk-shell/10.1016/j.nanoen.2017.01.033Received28October2016;Receivedinrevisedform12January2017;Accepted14January2017⁎Correspondingauthors.E-mailaddresses:jeffni@(J.Ni),lli@(L.Li).Nano Energy 33 (2017) 213–220

氟化钇钠电致变色

氟化钇钠电致变色

氟化钇钠电致变色

1.引言

1.1 概述

氟化钇钠是一种具有特殊性质的化合物，它可以在外加电场的刺激下发生电致变色现象。电致变色是指当氟化钇钠受到电场的作用时，其颜色会发生明显的变化。这种特殊的变色现象使得氟化钇钠在光电子器件、显示技术和光学应用等领域具有广泛的潜在应用前景。

氟化钇钠的电致变色机制是通过调控其内部电子结构来实现的。在无外加电场的情况下，氟化钇钠的晶体结构稳定，电子结构处于平衡状态。然而，当外加电场作用于氟化钇钠时，电子的能级会发生变化，导致氟化钇钠的能带结构发生改变。这种能带结构的改变引起了电子的重新排布和能级的移动，从而导致氟化钇钠的光学性质发生变化，进而引起颜色的变化。

氟化钇钠的电致变色现象不仅具有科学研究意义，还有着广泛的实际应用前景。例如，在光电子器件方面，氟化钇钠可以作为可调控光学薄膜材料，实现在不同电场下的光学特性变化，从而用于可调谐滤光器、光学开关等器件的制造。在显示技术方面，氟化钇钠可以用于制造电致变色显示器，实现高分辨率、低功耗的显示效果。此外，氟化钇钠还可以应用于光学传感器、信息存储等领域，具有广泛的应用潜力。

总之，氟化钇钠的电致变色现象是一项具有重要研究价值和广泛应用前景的科学现象。深入理解氟化钇钠的电致变色机制，将有助于推动光电子器件、显示技术等领域的发展，并为新型光学材料的设计和合成提供指导。

1.2文章结构

文章结构是指文章的整体框架和组织方式，合理的文章结构能够使读者更加清晰地理解文章的内容和逻辑关系。本文主要介绍氟化钇钠电致变色的相关知识，其文章结构主要包括以下几个部分：

1. 引言：通过概述和目的部分来引入文章的主题和背景，向读者介绍氟化钇钠电致变色的基本情况和研究意义。

2. 正文：在这一部分中，将详细介绍氟化钇钠的性质和电致变色机制。可以从以下几个方面展开论述：

- 2.1 氟化钇钠的性质：介绍氟化钇钠的结构、物理性质和化学性质，包括晶体结构、熔点、溶解性等基本信息。

Effect ofthedanglingbondontheelectronicandmagneticproperties

Effect ofthedanglingbondontheelectronicandmagneticproperties

Effectofthedanglingbondontheelectronicandmagneticproperties

ofBNnanoribbon

Fang-LingZhenga,YanZhangb,Jian-MinZhanga,n,Ke-WeiXuc

aCollegeofPhysicsandInformationTechnology,ShaanxiNormalUniversity,Shaanxi,Xian710062,PRChinabLaboratoireSPMS,E´coleCentraleParis,CNRS-UMR8580,92295Chˆatenay-MalabryCedex,FrancecStateKeyLaboratoryforMechanicalBehaviorofMaterials,XianJiaotongUniversity,Shaanxi,Xian710049,PRChina

articleinfo

Articlehistory:Received19August2010Receivedinrevisedform15October2010Accepted13January2011Availableonline21January2011

Keywords:A.NanostructuresA.SemiconductorsC.AbinitiocalculationsD.ElectricalpropertiesD.Magneticpropertiesabstract

TheeffectofthedanglingbondontheelectronicandmagneticpropertiesofBNnanoribbonwithzigzagedge(ZBNNR)andarmchairedge(ABNNR)havebeenstudiedusingthefirst-principlesprojector-augmentedwave(PAW)potentialwithinthedensityfunctiontheory(DFT)framework.ThoughZBNNRorABNNRwithHatomterminatedatbothedgesisnonmagneticsemiconductor,thedanglingbondinducesmagnetismfortheZBNNRwithbareNedge,bareBedge,bareNandBedges,theABNNRwithbareNedgeandbareBedge.However,theABNNRwithbareNandBedgesisstillnonmagneticsemiconductorduetothestrongcouplingofthedanglingbondsofdimericNandBatomsatthesameedge.ThemagneticmomentofZBNNRwithbareN(B)edgeisnearlyhalfthemagneticmomentofABNNRwithbareN(B)edge.SuchahalfrelationshipisalsoexistedinthenumberofthedanglingbondstatesappearedaroundtheFermilevelinthebandstructures.Furthermore,thedanglingbondstatesalsocausebothZBNNRandABNNRwithbareNedgeatransitionfromsemiconductingtohalf-metallicandthusacompletely(100%)spin-polarization,whilecausebothZBNNRandABNNRwithbareBedgeaswellasABNNRwithbareNandBedgesonlyadecreaseintheirbandgap.&2011ElsevierLtd.Allrightsreserved.