Engineering4(2018)787–795Contents lists available at ScienceDirectEngineeringResearch
PrecisionEngineering—Article
FabricationofPeriodicNanostructuresUsingAFMTip-Based
Nanomachining:CombiningGrooveandMaterialPile-UpTopographies
YanquanGenga,b,YongdaYana,b,?,JiqiangWangb,EmmanuelBrousseauc,?,YanwenSunb,YazhouSunbaKeyLaboratoryofMicro-systemsandMicro-structuresManufacturingoftheMinistryofEducation,HarbinInstituteofTechnology,Harbin150001,ChinaCenterforPrecisionEngineering,HarbinInstituteofTechnology,Harbin150001,ChinacCardiffSchoolofEngineering,CardiffUniversity,CardiffCF243AA,UKbarticleinfoabstract
This paper presents an atomic force microscopy (AFM) tip-based nanomachining method to fabricate periodic nanostructures. This method relies on combining the topography generated by machined grooves with the topography resulting from accumulated pile-up material on the side of these grooves. It is shown that controlling the distance between adjacent and parallel grooves is the key factor in ensur-ing the quality of the resulting nanostructures. The presented experimental data show that periodic pat-terns with good quality can be achieved when the feed value between adjacent scratching paths is equal to the width between the two peaks of material pile-up on the sides of a single groove. The quality of the periodicity of the obtained nanostructures is evaluated by applying one- and two-dimensional fast Fourier transform (FFT) algorithms. The ratio of the area of the peak part to the total area in the normal-ized amplitude–frequency characteristic diagram of the cross-section of the measured AFM image is employed to quantitatively analyze the periodic nanostructures. Finally, the optical effect induced by the use of machined periodic nanostructures for surface colorization is investigated for potential applica-tions in the ?elds of anti-counterfeiting and metal sensing.
ó 2018 THE AUTHORS. Published by Elsevier LTD on behalf of Chinese Academy of Engineering and Higher Education Press Limited Company. This is an open access article under the CC BY-NC-ND license
Articlehistory:Received28April2018Revised15June2018Accepted18September2018Availableonline26September2018Keywords:AtomicforcemicroscopyNanomachiningPeriodicnanostructureSingle-crystalcopper1.IntroductionTherapiddevelopmentofnanotechnology-baseddeviceshasledtoperiodicnanostructuresbeingwidelyreliedonforarangeofapplicationsincludingthedesignofsolarcells[1,2],nanoscaleplasmonicstructures[3–5],andthestructuralcolorationofmetal-licsurfaces[6,7].However,thecontrolledfabricationofperiodicnanostructureswithspeci?cdimensionsstillpresentsimportantchallenges.Researchershaveusedseveralmethodstoproduceperiodicnanostructures,includingnanoimprintlithography[8],focusedion-beammilling[9],directmechanicalmachining[10],andelectrochemicalmachining[11].However,thesemethodsareusuallyassociatedwithcomplicatedoperations,lowthroughput,lowmachiningaccuracy,and/orsigni?cantimplementationcost.Therefore,thedevelopmentofamanufacturingapproachtofabri-cateperiodicnanostructureswithaccuratedimensionsisstillanareaofimportantresearchinterest.?Correspondingauthors.E-mailaddresses:yanyongda@hit.edu.cn(Y.Yan),BrousseauE@cardiff.ac.uk(E.Brousseau).Theatomicforcemicroscopy(AFM)tip-basednanofabricationtechniquehasbeenshowntobeanattractivealternativetoachieveone-dimensional(1D),two-dimensional(2D),andeventhree-dimensional(3D)nanostructuressuccessfully[12–15].Inparticular,forthefabricationof3Dnanostructures,severalAFMtip-basednanomachiningapproacheshavebeenproposed,suchasthermochemicallithography[16],localanodicoxidation[17],tribochemistry-inducedetching[18],andnanomechanicalmachining[19].Amongthese,thenanomechanicalmachiningmethodhastheadvantagesofbeingreadilyimplementedandbeingthemost?exiblemeansoffabricating3Dnanostructures.Itisreasonabletoassumethatifamethodhasbeenproventobesuitableforgenerating3Dnanostructures,itcouldbefurtheremployedtoproduceperiodicnanostructures.Inthiscontext,researchershavealreadyattemptedtoimplementtip-basednanomechanicalmachiningtofabricatesinusoidalperiodicnanostructures[19–22].We?rstproposedtheintegrationofaclosed-loopnanoscaleprecisionstagewithanAFMinordertomechanicallyfabricatesuchsurfacetopographies[19].However,inourstudy,thedimensionsofthenanostructurescouldnotbedeterminedbeforemachining.Tohelpovercomethisissue,we788Y.Gengetal./Engineering4(2018)787–795developedatheoreticalmodeltorevealtherelationshipbetweenthenormalloadandthemachineddepth[20].Basedonthismodel,thenormalloadcouldbepredictedinordertoachievetheexpectednanostructuredimensions.Moreover,itwasconcludedinnumer-ouspreviousstudies[20,23,24]thatthemachineddepthisnotonlydependentontheappliednormalload,butalsoin?uencedbythefeedvalueduringthescratchingprocess.Thus,keepingthenormalloadconstantduringthemachiningprocessandenablingthefeedtobevariedinordertocontrolthemachineddepthweresubse-quentlyconsidered[21,22].Thismethodcouldbeimplementedtomachinelarge-scaleperiodicnanostructuresontheradialfaceofaxisymmetriccomponents,andtoimprovetheprocessingef?ciencyoftheAFMtip-basedmachiningtechnique.However,itwasnoticedthattheslopeofthefabricatedstructureshadtoberestrictedtoarangefromà12°to12°,inordertoguaranteeamachiningerrorwithin10%.Thismeansthatforagivenamplitudeofthestructure,theperiodcannotbelessthanalimitingvalue[21].Forexample,ifthedesiredamplitudeis125nm,thentheminimumvalueoftheperiodforthesinusoidalwaveformsis3.74lm.Thisisanimportantlimitationofthe‘‘milling-like”machiningmode,despitethepossibilityofgeneratingperiodicnanostructureswithit.Recently,amethodwasproposedbyHeetal.[25]tofabricatearraysofgrooveswithaperiodof30nm.Inthatcase,dynamicplowinglithographywasemployedtoscratchapolymerthin?lm.However,itwasdif?culttoobtainanamplitudegreaterthan20nmduetothelimitationintheenergyinputbythetip;inaddition,therewereissueswithunderstandingthespeci?cmaterial-removalmechanisminthatstudy.Itisimportanttonotethatmaterialaccumulationintheformofpile-upsonthesidesofthemachinedgrooveswasakeyfactorinthestudyreportedbyHeetal.[25].Wehavefoundthatthestaticmachiningmethodcanalsobeusedtoscratchsingle-crystalcopper,andthatitisaccompaniedbytheformationofmaterialpile-upalongcertainscratchingdirections.Interestingly,theamplitudebetweenthetopofapile-upandthebottomofagroovecanreacharelativelylargerange[26].Thus,wearguethatconventional(i.e.,static)AFMtip-basednanomachiningcanbesuitableforthefabricationofperiodicnanostructuresbyimplementinga‘‘combinedwriting”approach.Morespeci?cally,weproposethatthetopographygeneratedbythemachinedgroovesandthetopographyresultingfromthepile-upformationcanbecombined,leadingtothemanufactureofcontrolledperiodicnanostructures.Inthisstudy,theAFMtip-basedstaticmachiningmethodisusedtofabricatenanostructuresbymeansoftheproposed‘‘com-binedwriting”approachonasingle-crystalcoppersurface.Theperiodicityoftheobtainednanostructuresisevaluatedby1Dand2DfastFouriertransform(FFT)algorithms.Finally,thecolorizationofthemachinedperiodicnanostructureisexamined.2.Experiments2.1.ExperimentalsetupAcommercialAFM(DimensionIcon,Bruker,Germany)wasemployedinthisstudy.TheNanoManmoduleofthisAFMsystemwasselectedtoconductallthescratchingoperations.Inthismod-ule,thescratchingtrajectoryoftheAFMtipiscontrolledbyapiezoelectrictube(PZT),andthemaximummotionrangesofthePZTinthexandydirectionsare90and90lm,respectively.Toavoidtipwearduringthescratchingprocess,adiamondAFMtip(PDNISP,Bruker,Germany)wasselected.Thecantileverofthisdia-mondtipismadeofstainlesssteel,anditscalibratedspringcon-stantisgivenas275Námà1bythemanufacturer.Theradiusofthisdiamondtipwasevaluatedas110nmusingthetipblind-reconstructionmethod[27].Thesampleusedinthisstudywassingle-crystalcopperwitha(110)crystallographicplane(HefeiKeJingMaterialsTechnologyCo.,China).Priortoitsdelivery,thesamplewaspolishedbythemanufacturertoaresultingroughness(Ra)lessthan5nm,asmeasuredwithtapping-modeAFM.Theradiusofthediamondtipwasassumedtobeconstantduringthescratchingprocessduetothemuchhigherhardnessofthedia-mondcomparedwiththesoftercoppersample.Aftermachining,theobtainednanostructuresweremeasuredbyasiliconnitridetipwithanormalspringconstantof0.35Námà1incontact-modeAFM.Beforeboththemachiningandtheimagingsteps,thesamplewasultrasonicallycleanedinalcoholsolutionfor10min.2.2.MethodologyAccordingtoourpreviousstudy[26],materialaccumulatesonthesidesofthegroovesintheformofpile-upwhensingle-crystalcopperwitha(110)crystallographicplaneisscratchedusinganAFMdiamondtip.Inthatstudy,the‘‘edge-forward”direc-tionwasemployedasthescratchingdirection.Materialpile-upsformonbothsidesofthegroovewiththisselectedscratchingdirection[28].AsdiscussedintheIntroduction,theapproachesuti-lizedinpreviousstudiestoachieveperiodicnanostructuresbycontrollingtheappliednormalloadandthefeedvaluewererela-tivelytime-consumingandwerelimitedbyaminimumachievableperiodofaround2lm.Forthesereasons,weproposeanovelandsimpleAFMtip-basednanomechanicalmachiningmethodtofabri-catesuchnanostructures.Ourmethodreliesonthecombinationofmaterialaccumulationandthemachinedgroove,asshowninFig.1.Thedetailedrealizationofthemachiningprocessofoneperiodicnanostructureisdescribedasfollows:Step1:ThediamondAFMtipapproachesthesamplesurfaceuntilapresetnormalloadisattained.ThisnormalloadisFig.1.(a)Schematicofthemachiningprincipleemployedtogenerateperiodicnanostructures;(b)cross-sectionofplaneI.V:velocity.Y.Gengetal./Engineering4(2018)787–795789subsequentlykeptconstantbythefeedbackloopoftheAFMsys-temduringthemachiningprocess.ThediamondtipiscontrolledbythePZToftheAFMsysteminordertoscratchthesamplesur-facetoachieveonegroove.Thelengthofthemachinedgrooveisusedtocontrolthewidthoftheperiodicnanostructure.Step2:Afteragrooveismachined,thediamondAFMtipismovedtothestartpointofthesubsequentgroovebytappingmodeinordertoavoiddestroyingthesamplesurfaceduringtherepositioningofthetip.Thisnewgrooveiscutparalleltothepre-viousoneandtheoffsetdistanceispreciselycontrolledinordertomaketheadjacentmaterialpile-upsofthesetwomachinedgroovescombineintoonepeak.Theoffsetdistancebetweentheadjacentmachinedgroovesisde?nedasthefeedvalueinthisstudy.Thefeedvalueshouldbeevaluatedbasedontherelation-shipbetweenthenormalloadandthetotalwidthofthemachinedgroove.Step3:Step2isrepeateduntilthemachiningprocessoftheperiodicnanostructureiscompleted,asshowninFig.1(b).Thesumofthefeedvaluesisutilizedtodeterminethelengthoftheperiodnanostructure.thegrooves,asshowninFig.2(b).Thesumoftheheightofthematerialpile-upandthemachineddepthisde?nedastheamplitudeofthestructure.Tostudytherelationshipbetweenthepro?leofthemachinedgrooveandtheappliednormalload,eightnanogroovesweremachinedona(110)single-crystalcoppersur-facewithnormalloadsfrom80to150lNanda?xedscratchingvelocityof3lmásà1.Fig.3showstheexperimentalrelationshipbetweenthemachineddepth,amplitude,period,andappliednor-malload.Itcanbeobservedthatthemachineddepthofthegroovesrangesfrom180to300nm,whiletheamplitudeisalmosttwicethevalueofthemachineddepth.Theachievedperiodrangesfromabout1.1to1.6lm.Basedontheseresults,apolynomial?ttingwasusedtodescribetheserelationships,asexpressedinEqs.(1)–(3).y1?22:4857t2:20685xà0:00245x2y2?21:61512t5:03543xà0:00874x2y3?0:33705t0:01059xà0:0000135119x2e1Te2Te3T3.Resultsanddiscussion3.1.RelationshipbetweenthefeedandthetotalwidthofthegrooveAsmentionedabove,thefeedvalueischosenaccordingtothetotalwidthofthegroove,whichisrelatedtotheappliednormalload.Thus,therelationshipbetweentheappliednormal,themachineddepth,andthetotalwidthofthegrooveshouldbeinves-tigated?rst.Fig.2showsanAFMimageandthecorrespondingcross-sectionofatypicalnanogroovemachinedwithanormalloadof120lNandascratchingspeedof3lmásà1.Thetotalwidthofthegrooveisde?nedastheperiodofthegroove,whichisthedis-tancebetweenthetwopeaksofmaterialpile-uponbothsidesofFig.2.(a)AFMimageand(b)correspondingcross-sectionofatypicalgroovemachinedwithanormalloadof120lNandascratchingspeedof3lmásà1.wherey1,y2,andy3representthemachineddepth,amplitude,andperiodofthegrooves,respectively,andxistheappliednormalload.The?ttedcurvesareshowninFig.3.Next,anormalloadof150lNwasselectedinordertostudytherelationshipbetweenthefeedandthetotalwidthofthegroove—thatis,theperiodofthegroove—inthecaseofmachiningtwoadja-centparallelgrooves.FromEq.(3),theperiodofthegroovecanbecalculatedas1.635lm.Fourfeedvalueswerechosentoconducttheexperimentaltests:0.25,0.75,1.635,and2lm.TheAFMimagesofthemachinedstructuresandthecorrespondingcross-sectionsareshowninFig.4.Itcanbeobservedthatonlyonegroovecanbeobtainedwhenscratchingwithafeedvalueof0.25lm.ApossiblereasonisthatthefeedvalueinthiscaseistooclosetotheradiusoftheAFMtip(about0.11lminthisstudy),sothesecondscratchingpathsimplyendsupoverlappingthepreviousmachiningtrajectory.Forafeedof0.75lm,althoughthisvalueissmallerthanthetotalwidthofthegroove,itismuchlargerthantheradiusofthetip.Thus,asshowninFig.4(b),theresultingadjacentscratchpathsareseparatedfromeachother.Duetotheoverlappingoftheadjacentscratchedgroove,theheightoftheleftsideofmaterialpile-upforthesecondgrooveissmallerthanthatofthepreviousmachinedgroove.Whenthefeedvalueislargerthanthetotalwidthofthegroove,whichwasselectedas2lminthisstudy,theadjacentscratchpathsarenotoverlapped,asshowninFig.4(c).Itcanbefurtherobservedthatthereisasmallgapbetweenthetwomaterialpile-upsfortheadjacentmachinedgrooves.DuetothelimitationofthegeometricalsizeoftheAFMtip,thisgapcannotbeaccuratelymeasuredbythetraditionalAFMscanningprocess.Finally,afeedvalueequaltothetotalwidthofthegroove(i.e.,1.635lm)wasselectedtoconducttheFig.3.(a)Machineddepth,(b)amplitude,and(c)periodofthescratchedgroovesasafunctionofthenormalload.Theredsolidlineisthe?ttedsecond-orderpolynomialcurves.790Y.Gengetal./Engineering4(2018)787–795Fig.4.(Leftcolumn)AFMimagesofmachinedstructureswhenscratchingtwoadjacentandparallelgrooves,and(rightcolumn)correspondingcross-sectionsforfeedvaluesof(a)0.25lm,(b)0.75lm,(c)2lm,and(d)1.635lm.scratchingtest.ThecorrespondingAFMimageofthemachinedgrooveisshowninFig.4(d).Inthiscase,theadjacentmaterialpile-upscanexactlyconnectwitheachotherandaregularperiod-icityisobserved.Moreover,theheightofthecombinedmaterialpile-upisslightlylargerthanthatachievedwithsingle-groovescratching.Thisisprobablybecausethematerialvolumeofthecombinedpile-upislargerthanthematerialaccumulationgeneratedforasinglegroove.Wealsofabricatedadditionalperiodicnanostructures,thistimewithagreaternumberofparallelgrooves.Inthiscase,anormalloadof100lNandascratchingvelocityof3lmásà1wereselected.UsingEq.(3),thetotalwidthofthegroovewaspredictedtobe1.271lm.Therefore,0.5,0.75,1.271,and1.5lmwerechosenasthefeedvaluesforthesenanoscratchingtests.TheAFMimagesandcorrespondingcross-sectionsareshowninFig.5,withtheresultsforthefeedsof0.5and0.75lmbeingshowninFig.5(a)and5(b),respectively.SimilartothesituationshowninFig.4(b),Fig.5.(Leftcolumn)AFMimagesofthemachinedperiodicstructuresand(rightcolumn)correspondingcross-sectionsforfeedvaluesof(a)0.5lm,(b)0.75lm,(c)1.271lm,and(d)1.5lm.thesetwofeedvaluesaresmallerthanthetotalwidthofasinglescratchedgroovebutmuchlargerthantheradiusoftheAFMtip.Thesetwo?guresshowthatprocessedmaterialscan?llthepreviousscratchingpathandtherebyreducetheamplitudeoftheperiodicstructures.Inaddition,duetomaterial?llingthepre-viousgroove,thestructureismainlyabovethesamplesurface.Forthefeedvalueof0.5lm,theamplitudeandperiodofthemachinedstructuresarearound100and500nm,respectively,whileforthefeedvalueof0.75lm,theamplitudeandperiodarearound150and730nm,respectively.Therelativelylargeamplitudeofthestructurethatwasmachinedwiththefeedvalueof0.75lmcouldbeduetoalargervolumeofmaterialbeing?lledinthepreviousgrooveasaconsequenceoftheincreasedfeed.Fromthecross-sections,itcanbeobservedthatagroovewithasigni?cantdepthofaround190nmcanbegeneratedontherightsideoftheperiodicstructureforbothcases.Thisisbecauseitisthelastgroovetobemachinedinasingleperiodicstructure.Moreover,nanostructuresY.Gengetal./Engineering4(2018)787–795791thataremuchsmallerthantheinitialgroovecanbeobtainedusingarelativelysmallfeed.Fig.5(c)showstheperiodicstructurethatisfabricatedusingafeedequaltothetotalwidthoftheinitialgroove—thatis,1.271lm.Itcanbeseenthatamoreconsistentamplitudeandperiodforthestructurecanbeachievedinthiscase.Theamplitudeisaround390nmandtheridgesonbothextremi-tiesofthestructureareslightlylowerthantheridgesintheothercases.Thesameresultwasobservedinthepreviousexperimentswithonlytwogrooves.3.2.EvaluationoftheperiodicityofthemachinednanostructuresInordertoevaluatetheperiodicityofthemachinednanostruc-tures,the2DFFTapproachwasappliedtotheAFMimagesusingtheSpectrum2DmoduleofthecommercialsoftwareNanoscopeAnalysisfromBruker.Fig.6showsthe2DFFTresultsforthemachinedstructuresdescribedinFig.5.Itcanbeobservedfromthe2DFFTresultsthatthebrightlinesareperpendiculartothehorizontalandverticaldirections,whichresultsfromthestriatedstructure.AsshowninFig.6(a–c),therearetwomainbrightlinesonbothsidesofthecentralpointoftheimage,whicharevertical.Thisindicatesthatthepowerspotsaremainlyconcentratedononlyonespectrumandthatthemachinedstructuresmainlycom-priseawaveformwithasinglespectralsignature.Thepowerspotsaremoreconcentratedforthe2DFFTofthestructuremachinedwithafeedvalueof1.271lm,comparedwiththoseobtainedforthestructuresscratchedwithfeedvaluesof0.5and0.75lm.Thismeansthatthestructuremachinedwithafeedvalueof1.271lmshowsbetterperiodicity.Moreover,thedistancebetweenthebrightlineandthecentralpointofthe2DFFTimagedecreasesasthefeedvalueincreasesintherangefrom0.5to1.271lm.Thismeansthattheperiodofthestructureincreaseswithanincreaseinfeedvalue—a?ndingthatagreeswellwiththeearlierdiscussionofthecross-sectionsshowninFig.5.Forthe2DFFTimageofthestructuremachinedwithafeedvalueof1.5lm,threeobviousbrightlinescanbeseenonbothsidesofthecentralpointoftheFig.6.2DFFTresultsoftheperiodicnanostructuresmachinedusingfeedvaluesof(a)0.5lm,(b)0.75lm,(c)1.271lm,and(d)1.5lm.image.Thisindicatesthatthemachinedstructurecompriseswave-formswithseveralspectralsignatures.Inordertoquantitativelyanalyzetheperiodicityofthemachinednanostructures,1DFFTwasalsoselectedtoconductthecalculationprocess.Thecross-sectionofthemachinedstructurewasutilizedtocarryoutthe1DFFTprocess.Inthemeasurementprocessofthemachinedstructure,thereare256samplingpointsforonecross-section.Thexcoordinatevaluesforthesesamplingpointsweremappedtothefrequencyaxisoftheamplitude–frequencycharacteristicdiagramobtainedbytheFouriertransform.ThecorrespondingamplitudeswerecalculatedbyFouriertransformingtheycoordinatevaluesforthesesamplingpoints.Theobtainedpointsintheamplitude–frequencycharacter-isticdiagramwereconnectedtoformacontinuousspectrum,whichcanbeusedtoquantitativelyanalyzetheperiodicityofthemachinednanostructures.Duetothevariationoftheheightsofthematerialpile-upsandthemachineddepthsforthemachinedstructures,theamplitudesshownintheamplitude–frequencycharacteristicdiagramscalculatedbytheFFTprocesswerediffer-ent.Inordertoconductaquantitativeanalysis,theobtainedamplitudeshadtobenormalizedintherangefrom0to1.Inthisstudy,weproposeanareacalculationapproachtoeval-uatetheperiodicityofthemachinednanostructure.Thedetailedcalculationprocessisasfollows:First,thetotalareabetweentheamplitude–frequencycurveobtainedbytheFFTprocessandthefrequencyaxisiscalculated,andisde?nedasS.Next,thepeakwiththelargestamplitudeintheamplitude–frequencycharacteristicdiagramisselected;theareabetweenthepeakpartandthefre-quencyaxisisalsocalculated,andisde?nedasS1.Thein?ectionpointsclosetothefrequencyaxisarechosenasthestartandendpointsforthepeak.Theratio,x,ofS1toSisemployedasafactortoevaluatetheperiodicityofthemachinednanostructure.Totesttheproposedmethod,asinusoidalcurveandarandomcurvewere?rstselectedtoimplementtheperiodicityanalysis.Thesinusoidalcurvewasobtainedbyasinusoidalfunctionofy?2sine2pxT,asshowninFig.7(a);thecorrespondingnormalizedamplitude–frequencycharacteristicdiagramisshowninFig.7(b).Usingthe‘‘trapz”functionintheMatlabsoftware,SandS1werecalculatedas0.251and0.251,respectively.Thus,xwasequalto1inthiscase.Therandomcurvewasobtainedbyafunctionofy=randperm(256)intheMatlabsoftware,asshowninFig.7(c).Thenormalizedamplitude–frequencycharacteristicdiagramforthiscaseisrepresentedinFig.7(d),andSandS1werecalculatedas3.955and0.514,respectively.Thus,xwascalculatedas0.039,whichisobviouslycloseto0.Thus,itcanbeshownthatthelargerxis,thebettertheperiodicityofthemachinedstructureis;there-fore,theproposedmethodcanbeusedfortheperiodicityanalysis.Theproposed1DFFTevaluationmethodwasusedtoquantita-tivelyanalyzetheperiodicityofthenanostructuresshowninFig.5.Forthecasesinwhichthefeedvaluewaslessthanthetotalwidthofthemachinedgroove,thelargedepthofthegrooveontherightsideofthestructuremayaffecttheevaluationprocess.Thus,inthesetwocases,thepro?leofthegroovewitharelativelylargedepthwasremovedfromthecross-sectionofthestructurebeingevaluatedbythe1DFFTprocess,asshownintheleftcolumnofFig.8(a)and8(b).Thecorrespondingnormalizedamplitude–frequencycharacteristicdiagramsareshownintherightcolumnofFig.8(a)and8(b).Anobviouspeakwasfoundinthenormalizedamplitude–frequencycharacteristicdiagram,whichindicatesthatthestructuresmachinedwiththefeedvaluesof0.5lmand0.75lmhaveameanfrequencyspectrum.Forthefeedvalueof0.5lm,SandS1werecalculatedas0.534and0.198,respectively,andxwascalculatedas0.371.Forthefeedvaluethatwasenlargedto0.75lm,SandS1werefoundtobe0.443and0.219,andxwascalculatedas0.494.Thisindicatesthatthenanostructuremachined
基于AFM 探针的纳米加工技术制备周期性纳米结构 - 沟槽和材料堆积形貌相结合 - 图文
