原子力显微镜AFM原理及操作手册

Page 1 Asylum Research 2014 Atomic Force Microscopy Part 2: Standard modes and applications Asylum Research Page 2 Asylum Research 2014 Common modes of operation A few applications A few NEW applications ! and some cool images Principles of AFM Page 3 Asylum Research 2014 Force measurements Contact mode AC (tapping) mode and sources of error in measurements Modes of Operation Page 4 Asylum Research 2014 Sample Light Source Focusing Optics Cantilever Position Sensitive Detector y x z Shake Piezo Vary the tip-sample separation, usually without feedback -5 0 Deflection (nm) -1.6-1.2-0.8-0.4 Z Position ( m) F = -kx Modes of Operation force curves Page 5 Asylum Research 2014 Defl Volts V or Deflection nm or Force N Force = (Defl Volts) * (Defl InvOLS) * (k) nNVnm/V nN/nm Deflection Tip sample distance nm Modes of Operation force curves Page 6 Asylum Research 2014 k = 21.4 0.4 pN/nm 15x10 -12 10 5 Power Spectrum (nm/Hz) 14kHz121086420 Frequency (kHz) 1 2 k A 2 1 2 kBT Equipartition theorem quantifies thermal (Brownian) motion Advantages -“standard” -non-destructive -easy to use Disadvantages: -must first calibrate sensitivity -values good to only 10% Spring constant calibration Modes of Operation force curves Page 7 Asylum Research 2014 Modes of Operation force curves Page 8 Asylum Research 2014 Arrays of Force curves can be used to calculate the local stiffness of a sample Modes of Operation force curves Page 9 Asylum Research 2014 6 4 2 0 -2 nm -4.8-4.6-4.4-4.2-4.0-3.8 m ARTIFACTS optical interference Page 10 Asylum Research 2014 20 15 10 5 0 -5 nm -50050 nm ARTIFACTS tip/substrate interaction Page 11 Asylum Research 2014 30 25 20 15 10 5 0 nm 0.20.0 m 0.5Hz 5 Hz 10Hz Velocity: Increasing velocity adds hysteresis between approach AC mode image in air parachuting good tracking ARTIFACTS: Too much force applied Page 24 Asylum Research 2014 Integral gain = 40 Integral gain = 2 Integral gain = 9 5um x 5um scan, 10um pitch VLSI calibration grid; AC mode image in air ARTIFACTS: Feedback loop effects (high gain) Page 25 Asylum Research 2014 48mV 66mV 500mV 30 25 20 15 10 5 0 302520151050 m 5um x 5um 100 um pitch VLSI calibration grid; AC mode image in air ARTIFACTS: Feedback loop effects (drive amplitude) Page 26 Asylum Research 2014 30 25 20 15 10 5 0 m 302520151050 m -20 -10 0 10 20 nm -200nm -150 -100 -50 0 Height 2520151050 m 30 25 20 15 10 5 0 m 302520151050 m -20 -10 0 10 20 nm -200nm -150 -100 -50 0 Height 302520151050 m ARTIFACTS: Scan rate effects Page 27 Asylum Research 2014 Images Applications measurements Page 28 Asylum Research 2014 250 nm scan DNA in liquid Images Page 29 Asylum Research 2014 Consecutive up and down scans of a single DNA molecule in buffer taken with a 30m lever at an amplitude of about 8. The nominal helix pitch is 3.4 nm, with a major groove width of 2.2 nm and a minor groove width of 1.2 nm. You can see 6 grooves along the 10 nm scale bar, so both the major and minor groove are clearly resolved. DNA in liquid Images Page 30 Asylum Research 2014 Courtesy of S. MacLaren and H. Wang University of Illinois at Urbana-Champaign. E. coli on glass 6 m scan Images Page 31 Asylum Research 2014 Live endothelial cells Dynamic Events: Before Treatment with Mannitol Image courtesy of Z. Blint and Dr. G. Vr, Institute of Biophysics, Szeged, Hungary Images Page 32 Asylum Research 2014 Dynamic Events: After Treatment with Mannitol Image courtesy of Z. Blint and Dr. G. Vr, Institute of Biophysics, Szeged, Hungary Images Live endothelial cells Page 33 Asylum Research 2014 Bacteriorhodopsin Found in cell membranes of Halobacteria Absorbs photons and pumps protons across the cell membrane Forms 2D crystalline patches that cover much of the cell B Because it has been extensively studied by AFM, it makes a great protein reference sample. Images Page 34 Asylum Research 2014 Extracellular face, 100 nm scan Bacteriorhodopsin Images Page 35 Asylum Research 2014 HeightLFM Varying coefficient of friction causes torsional or “lateral” bending Nanotribology Functionalized tips for chemical force microscopy Applications friction Page 36 Asylum Research 2014 M F M MoS2 Topographical 3D image of region of an MoS2crystal showing a single step Scan size - 500 x 500 nm2 Applications roughness Page 37 Asylum Research 2014 M F M Roughness measurement of the lower step Topographical 3D image of region of an MoS2crystal showing a single step Scan size - 500 x 500 nm2 Applications roughness Page 38 Asylum Research 2014 Range: RT to 300C 0.2C precision, 0.5C accuracy Closed loop temperature control Fully sealable Polypropylene Diblock copolymer Applications heating Page 39 Asylum Research 2014 Sub-picoAmp to Amp range Sample bias from -10 to +10 V Simultaneously map current and topography Rf Rsample Vbias Carbon nanotube - + Vout Applications conductive AFM Page 40 Asylum Research 2014 Sub-picoAmp to Amp range Locally probe IV response from a specific point Bias ramp options: triangle, sine, square, or custom wave ZnO doped with Eu Current nA Bias mV Applications conductive AFM Page 41 Asylum Research 2014 VideotapeHard driveGarnet Two pass technique Provides a qualitative map of the magnetic field above a sample Variety of magnetic tips of varying coercivity and moment 500 nm 20 m 18 m Applications Magnetic force microscopy Page 42 Asylum Research 2014 Two pass technique Sensitive to conductors and insulators Lateral resolution affected by fly- height Applications Electric force microscopy Page 43 Asylum Research 2014 AC bias sent to tip (matched to o) Difference in potential causes cantilever oscillations Feedback sends DC bias to cantilever, nulling oscillations Quantitative measurement of the surfaces potential Trapped charge, surface polarization, workfunction, or applied voltage can be measured 10 m PCB board traces Applications Kelvin probe force microscopy Page 44 Asylum Research 2014 Electrical bias to tip in contact with the surface induces a mechanical response Applicable to piezo and ferroelectrics as well as many biological systems High voltage option allows the application of up to 220V to the sample PZT Applications piezoresponse force microscopy Page 45 Asylum Research 2014 Related to mechanical energy dissipation Can distinguish between hard and soft regions PDES Applications phase imaging Page 46 Asylum Research 2014 Array of force curves Automated extraction of materials properties (e.g. Elastic modulus) Applications force maps Page 47 Asylum Research 2014 Loss Tangent - Drop Testing tan Wloss Wstorage R. Lakes, Viscoelastic Materials, Cambridge (2009) Page 48 Asylum Research 2014 Applications Loss Tangent / AMFM Page 49 Asylum Research 2014 1.Adjust the pre-factor to make a known component be correct 2.Reference sample(s) 3.(Hertz, DMT, JKR) theory, dynamics of an oscillating cantilever Sample courtesy of Ken Strawhecker, Army Research Lab Applications AMFM fibers in epoxy Page 50 Asylum Research 2014 AMFM on Reinforced Composites: Kevlar in epoxy - radial Page 51 Asylum Research 2014 Cantilever driven at multiple resonant modes Contrast (dissipation?) not visible with any other techniques Able to image long and short range forces simultaneously Hard disk Collagen Applications multifrequency Page 52 Asylum Research 2014 Load picture files, make freehand or geometrical sketches Closed loop position control Vector based or bit-mapped modes Force can be either held constant or varied as desired GraphiteCarbon nanotube Applications nanomanipulation Page 53 Asylum Research 2014 Load picture files, make freehand or geometrical sketches Closed loop position control Vector based or bit-mapped modes Force can be either held constant or varied as desired c PolycarbonateSAM on Au Applications nanolithography Page 54 Asylum Research 2014 Ferroelectric polarization modified through application of bias Domain reversals can be written Bit mapped color can be use to control the applied voltage during lithography Applications nanolithography (PFM) Page 55 Asylum Research 2014 40 nm sol-gel BFO thin film PFM phase image. +6 V in the yellow phase regions and -6 V in the purple phase regions thus switched the domains with downwards and upwards polarization respectively. Who is this a picture of? Applications nanolithography (PFM) Page 56 Asylum Research 2014 6 5 4 3 2 1 0 mm -1.0 -0.5 0.0 0.5 1.0 nm The Creation of Adam Oxidation nanolithography on Silicon (15 m scan). Original artwork by Michelangelo (Sistine Chapel) Applications nanolithography (oxidation) Page 57 Asylum Research 2014 5 4 3 2