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AtomicForceMicroscopyIntroduction,Foundations,
InstrumentationandMulti-disciplinaryApplications
Aseriesoflecturesby
Dr.KhaledKaja
DNAdoublehelixstructureresolved
AlkanechainsC36H74StudyofGraphene’sstructural,electricalandchemicalproperties
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AbstractAtomicForceMicroscopy(AFM)hasrapidlygrownsinceitsinventionin1986tobecomeanessentialtechniqueforsurfacecharacterizationinlargevarietyofresearchfieldsinnano-electronics,materialssciences,polymers,softmatter,chemistryandbio-technologicalapplications.AFMenablestheinvestigationofsurfaceandsub-surfacepropertiesofsamplesatanunprecedentedscaleoffewnano-metersandultimatelyattheatomiclevel.
Theimportanceofthistechniqueinvirtuallyallfieldsofresearchraisestheneedofaclearunderstandingofitsfundamentalfoundationsandprinciples.Thedevelopmentofnumerousmodestailoredtovariousapplicationsmakesitessentialtounderstandthedifferentoperationprinciplestoprovidegraduatestudentswithsufficienttheoreticalandexperimentalbackgroundtopropeltheirresearchforwardandexplorenovelapplicationsandpublishableresults.
TowhomtheselecturesareaddressedTheselecturesareintendedforundergraduateandgraduatestudentswhoarelookingtotaketheendeavorinthefieldofnano-sciences.ThiswillcoverstudentsworkinginthefieldofPhysics,Electronics,ElectricalEngineering,Polymers,Organicchemistry,SoftmatterandBiology.
ThetopicsaddressedintheselecturesaretailoredtointroducethestudentstothefieldofScanningProbeMicroscopy(SPM)fortheiruseandapplicationinavarietyofsystems’characterizationandstudies.Mainbeneficialofthisare:
• Masterstudentspreparingtoenrollinfutureresearchstudiesinvolvingcharacterizationandinvestigationatthenano-scale.
• PhDstudentsinthecourseoftheirresearchstudies.• Scientistsandresearcherslookingtoexpandtheirfieldandseekingadeep
understandingoffundamentalaspectsofAFMaswellasinstrumentationaspectsanddevelopment.
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Outline
Thisseriesoflecturesaredistributedtotwomainmodules:
AFMI:Introduction&Foundations–AtheoreticalbackgroundinAtomicForceMicroscopy.
AFMII:Multi-modal&Multi-disciplinaryApplications–Anin-depthstudyofAFMbeyondtopographyanditsapplicationsinnano-electronics,nano-magnetism,chemistryandbio-technology.
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CoursesContent
AFMI
Introduction&FoundationsAtheoreticalbackgroundinAtomicForceMicroscopy
1. IntroductiontoScanningProbeMicroscopy:
1.1. HistoricalBackground1.2. TheInventionoftheScanningTunnelingMicroscope:principle1.3. TheNeedforaForceMicroscopy:inventionoftheAFM1.4. WhatisanAFMandwhatdoesitmeasure?Overviewdescription1.5. AFMandNanosciences:applicationsoverviewandinterests1.6. OverviewofAFMmodesandexperimentaladaptations
2. ForcesinAtomicForceMicroscopy:2.1. OverviewofForcesfeltbyanAFMprobe2.2. ElectrostaticForces:
2.2.1. Coulomb’slawforpointcharges2.2.2. Electrostaticpotentialenergy
2.3. Moleculardipolemoments2.4. Dipolemomentsinexternalelectricfields2.5. SimplemodelsforMolecule-Moleculeinteractions:
2.5.1. InteractionofanIonwithamolecule2.5.1.1. Ioninteractingwithafixedpolarmolecule2.5.1.2. Ioninteractionwithapolarmoleculefreetorotate2.5.1.3. Induction:thepolarizationofanon-polarmolecule2.5.1.4. Interactionofapointchargewithanon-polarmolecule
2.5.2. Molecule-Moleculeinteractions2.5.2.1. Interactionoftwopolarmolecules2.5.2.2. Angle-averagedinteractionbetweentwopolarmolecules2.5.2.3. Interactionbetweenadi-polarmoleculeandanon-polarmolecule2.5.2.4. Interactionbetweentwonon-polarmolecules
2.6. VanderWaalsforcesbetweenmacroscopicobjects2.7. SurfaceEnergy,AdhesionandHamakerconstant2.8. TheDerjaguinApproximation2.9. Capillaryforces
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2.10. Frequencydependentdielectricfunction3. ContactMechanics
3.1. Elasticityofmaterials:3.1.1. Young’smodulus3.1.2. Poisson’sratio
3.2. Repulsiveinteractions:3.2.1. Hertzcontactmechanics3.2.2. DMTcontactmechanics3.2.3. JKRcontactmechanics3.2.4. Maugis–Dugdalemodel
3.3. Tip-surfacecontactinteractioninAFM:introducingforcespectroscopy3.3.1. Forcecurves3.3.2. Derivingsurfacepropertiesfromforcecurvesmeasurements
4. TheAFMinstrument4.1. GenericdescriptionofanAtomicForceMicroscopycomponents4.2. TheAFMprobe:
4.2.1. Deflectionofrectangularbeams4.2.2. Springconstant4.2.3. TheAFMcantileverasavibrationalbeam:eigenmodes4.2.4. Thermalvibrationsofthecantilever4.2.5. Spectralpowerdensity4.2.6. DesignandfabricationofAFMprobes:recenttrendsandneeds
4.3. TheAFMscanner:4.3.1. Measurementofdisplacements4.3.2. Steppermotors4.3.3. Theprocessofthetipapproach4.3.4. X-Yscanners:piezocreep
4.4. Thetransductionofthetip-sampleforces:4.4.1. Theopticalleverbeam4.4.2. Thephotodiodedetector4.4.3. Othermodesofmeasuringthedeflectionofthecantilever
4.5. Thefeedbackloop4.6. Thescanningofthesurface:methods4.7. TheformationofanAFMimage4.8. Imageprocessingtools4.9. Minimizingthethermaldrift4.10. Reducingfloorvibrations
5. Forcespectroscopy:Forcecurvesmeasurementsandcalibrations
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5.1. MeasuringforceversusZ-displacement5.1.1. Z-scannermovement:ramping
5.2. DerivingForce-distancecurves:sampledeformation5.3. Calibrationoftheforce:
5.3.1. Calibratingthespringconstantofthecantilever:methods5.3.2. Calibratingthedeflectionsensitivity5.3.3. Sourceoferrorsanduncertaintiesinthecalibrationprocess
5.4. Forcecurvesinair:5.4.1. Thejumpintocontact5.4.2. Thequestionofzeroforceposition
5.5. Forcecurvesinliquids5.6. Importanceofforcecurvesmeasurements:
5.6.1. Young’smodulusandadhesion5.6.2. Functionalizationoftheprobe5.6.3. Bindingandunfolding5.6.4. Longrangeinteractionsinvolved
5.7. Commondifficultiesinforcecurvesmeasurements5.8. Processingofforcecurvesdata
6. AFMincontactmode6.1. Imagingprocess:
6.1.1. Constantdeflection6.1.2. Feedbackgains6.1.3. Lateralforces–lateralforceimaging6.1.4. AdvantagesanddrawbacksofAFMincontactmodes6.1.5. Spatialresolutionincontactmode6.1.6. Nano-lithographyandlocalanodicoxidation
7. NoiseinAFM7.1. Externalsources7.2. Groundloopproblems7.3. Thermalfluctuations7.4. Measuringthesignaltonoiseratio7.5. Electronicnoises
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CoursesContent
AFMII
Multi-modal&Multi-disciplinaryApplicationsIn-depthstudyofAFMbeyondtopography
Applicationsinelectronics,magnetism,chemistryandbio-technology1. DynamicAFMmodes
1.1. VibrationsoftheCantilever1.1.1. Excitationmodes1.1.2. Probeholdersandinstrumentalconsiderations1.1.3. Eigenmodesandharmonics1.1.4. Energyofthecantilever’svibrationmodes1.1.5. Perspectives
1.2. Detectionofthecantilever’soscillations1.2.1. Drivingsignal,oscillationsandtheconceptofphase1.2.2. Lock-inamplifiers:reference,amplitudeandphaseoutputs
1.3. Oscillationsofanexcitedcantilever–vibrations1.3.1. Theconceptofresonance1.3.2. Theresponsecharacteristicsofanoscillatingcantilever
1.4. ThePhysicsoftheoscillatingcantilever1.4.1. Thespring-massmodel1.4.2. Thesimpleharmonicoscillator1.4.3. Dampedandforcedoscillatingcantilever1.4.4. Presenceofsurfaceinteractions:forcegradient1.4.5. Solutionoftheequationofmotion:amplitudeandphaseresponses1.4.6. Approximationofsmallamplitudes:linearapproximation
1.5. Tappingmode–Amplitudemodulation1.5.1. Principleofoperation1.5.2. Analysisoftheamplitude–Qfactor1.5.3. Sensitivity1.5.4. Analysisofthephase1.5.5. Calibration:amplitudevsdistanceandphasevsdistancecurves1.5.6. Attractiveandrepulsiveregimes:
1.5.6.1. TheLennardJonespotential
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1.5.6.2. Intermittentcontactregion1.5.6.3. Amplitudeandphasecurves1.5.6.4. Operationregimesandbi-stability
1.5.7. Spatialresolutionintappingmode:considerationsandregimes1.5.8. ImagingchannelsinTappingmode1.5.9. Phaseimagingandoriginofcontrast–compositionalmapping1.5.10. Non-linearityintheintermittentcontactmode
1.5.10.1. Viriel1.5.10.2. Harmonicmethod1.5.10.3. TheDuffingoscillator
1.5.11. Dampinginamplitudemodulation1.5.11.1. Timeconstant,Qfactorandequilibriumstates
1.5.12. Tappingmodeinliquid1.6. TheNon-contactmode–Frequencymodulation
1.6.1. Regionofoperation1.6.2. Frequencyshiftandnatureofforces1.6.3. PhaseLockLoop(PLL)–bandwidth1.6.4. Principleofoperation1.6.5. Damping,dissipationandfrequencyshifts1.6.6. Q-factorandProbes:Q-plus,Kolibriandlengthextensionresonators1.6.7. Operationinvacuum:advantages1.6.8. SpatialresolutioninNCAFM1.6.9. Derivingtheforcesfromthefrequencyshiftcurves
1.7. PeakForceTapping1.7.1. Semi-static,semi-dynamicmode:principleofoperation1.7.2. TheneedtointroduceanewwayofAFMoperation1.7.3. SinusoidalmodulationinZversusRampingmotion1.7.4. Forcecontrol1.7.5. Cantileverresponseandcalibrations1.7.6. Equationofmotion?
2. MechanicalProperties:modesandapplications2.1. Forcespectroscopy
2.1.1. MeasuringlocalElasticpropertiesandAdhesion2.1.2. Measuringthebendingmodulusofsuspendedstructures2.1.3. Examples
2.2. ForceVolumemode2.2.1. Principleofoperation2.2.2. Calibrations
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2.2.3. Imagingchannels:modulus,stiffness,adhesion2.2.4. Imageprocessing2.2.5. Challenges,limitationsanddifficulties2.2.6. Examples
2.3. Contactresonancemode2.3.1. Storageandlossmoduli2.3.2. Principleofoperation2.3.3. Modelsanddataanalysis2.3.4. Frequencyshiftsandtracking2.3.5. Examples
2.4. PeakForceQuantitativeNano-mechanicalMapping2.4.1. Principleofoperation2.4.2. Forceversusseparationcurves2.4.3. Calibrationoftheforceanddeflection2.4.4. Extractionandmappingofmechanicalproperties2.4.5. TheDMTmodelandcalibrations2.4.6. Challengesandperspectiveimprovements2.4.7. Examples
2.5. ApplicationsofmechanicalmeasurementsinAFM2.5.1. Materialssciences:polymers,novel2Dmaterials,nano-wiresandnano-tubes2.5.2. Biologyandbio-technology:cells,cancer,diseases,collagenandfibrils
3. Electricalandelectronicproperties:modesandapplications3.1. IntroducingtheLiftmodeoperation
3.1.1. Doublescanmode3.1.2. Linearscanmode
3.2. ElectricForceMicroscopy3.2.1. Capacitiveforceandmodulation3.2.2. Measuringindividualcharges3.2.3. Artifacts
3.3. Kelvin(Probe)ForceMicroscopy3.3.1. Theoryoftheworkfunction3.3.2. Importanceoftheworkfunctioninvariousapplications3.3.3. Generalprincipleofoperation:amplitudemodulationKPFM3.3.4. Resolutionandcontrast3.3.5. FrequencymodulationKPFM3.3.6. Probes3.3.7. Examples
3.4. PiezoresponseForceMicroscopy
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3.4.1. Principleofoperation3.4.2. Resonanceofdoublefixedrectangularlever3.4.3. Examples
3.5. ConductiveAFM(TUNA,PFTUNA)3.5.1. Modelsofcurrentflow3.5.2. MeasuringcurrentwithanAFMprobe:rangeofcurrents3.5.3. ContactmodesandPeakForcecurrentmeasurements3.5.4. Examples
3.6. ScanningCapacitanceMicroscopy3.6.1. Dopantprofiling3.6.2. Principleofoperation3.6.3. Calibrationandquantification3.6.4. Examples
3.7. ScanningSpreadingResistanceMicroscopy3.7.1. Principleofoperation3.7.2. Modelofthespreadingresistance3.7.3. Amplificationandelectronics3.7.4. Examples
3.8. ScanningMicrowaveImpedanceMicroscopy3.8.1. TheoryofMicrowaveandimpedance3.8.2. Principleofoperation3.8.3. Instrumentalimplementation3.8.4. Examples
3.9. ApplicationsofelectricalpropertiesmeasurementsinAFM4. Magneticproperties
4.1. MagneticForceMicroscopy4.2. Applicationsindatastorageandmemorytechnologies
5. Chemicalproperties5.1. FourierTransformInfra-Red(FTIR)5.2. NovelcombinationofAFMandFTIR
6. Multi-modalCombinations:measuringdifferentpropertiessimultaneously7. FastScanningAFM
7.1. Applicationsneeds7.2. Challengesandtechnologicaldifficulties7.3. PhysicsoffastscanninginAFM7.4. Technologicalsolutions:
7.4.1. Probe7.4.2. Scanner
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7.4.3. Modeofoperation7.5. Examples
8. Biologicalpropertiesandapplications8.1. Dynamicsofbiologicalphenomena8.2. Forcecontrol:imagingDNA8.3. Unfoldingofproteins–tipfunctionalization8.4. Elasticityofcellsandapplicationstocancerstudies8.5. Collagenandcollagenfibrils8.6. Electricalpropertiesofbiologicalsystems
9. Atomicandsub-atomicresolutioninAFM9.1. Physicalconsiderations9.2. Technicalconsiderations9.3. Samplepreparation9.4. Operatingmodesandenvironment9.5. Imagingmoleculesandelectronclouds9.6. Challengesanddifficulties
10. PracticalaspectsinAFM:tipsandtricks10.1. Probechoiceandcharacteristics10.2. Samplepreparationandapplications10.3. Complexsetupsanddevelopment10.4. Imageanalysis
10.4.1. Artifacts10.4.2. Dataprocessingandfiltering
10.5. HowtorecognizeagoodAFMandacorrectAFMimage
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Supportingreferencesandtextbooks
• “IntermolecularandSurfaceForces”,JacobN.Israeilachvili,ElsevierInc.• “FundamentalsofAtomicForceMicroscopy,Part1:Foundations”,Ronald
Reinferberger,WorldScientific.• “SurfacesandInterfacesofSolidMaterials”,HansLuth,SpringerStudyEdition.• “SolidStatePhysics”,N.Aschcroft,N.D.Mermin,CengageLearning.• “CoursdeMicroscopieaForceAtomique”,FrancoisBertin,CEA-Leti.• “TheFeynmanlecturesonPhysicsVol.II:Electromagnetism“
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TheLecturerDr.KhaledKajahasaPhDinNanophysicsfromthe French Authority of Atomic Energy (CEA)and the University of Grenoble I (JosephFourier) in France. He has been a researchassociate at the Swiss Federal Institute ofTechnology (ETH) in Zürich at the Chair ofNanotechnology.Heworkedasanapplicationsscientist at Bruker Nano-Surfaces (LeadingmanufacturerofAtomicForceMicroscopesandsurface characterisation techniques) based intheUK.Hewasresponsibleforallresearchandindustrial applications in the United Kingdom,Ireland, northern Europe region and themiddle-east. In the course of his research and
applications work, Dr. Kaja developed new operation AFM modes and demonstrated latestadvances and technologies in the field. He presented technical lectures in prestigiousuniversities in the UK such as Cambridge, Manchester, Leeds, Imperial College London andothers. He also organised numerous workshops and lectures in northern Europe andScandinavian regions such as Twente University in the Netherlands, University of Lunds inSwedenandHelsinkiinFinland.Dr.Kajahasover9yearsofexperienceinAtomicForceMicroscopytechniques.Hismainfieldsof interest are in Nanoelectrical and Nanomechnical techniques for surface characterisationwithafocusontwo-andlow-dimensionalmaterials.