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1、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 mod
2、e 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
3、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 nN V nm 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 14k
4、Hz121086420 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 Researc
5、h 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
6、 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 1 41 21 00 80 60 40 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 app
7、lied 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
8、 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
9、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 30 m lever at an amplitude of about 8 T
10、he 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 Universi
11、ty 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 B lint and Dr G V r Institute of Biophysics Szeged Hungary Images Page 32 Asylum Research 2014 Dynamic Events After
12、 Treatment with Mannitol Image courtesy of Z B lint and Dr G V r 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
13、 patches that cover much of the cell Bioweb wku edu 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 frict
14、ion 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
15、 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 300 C 0 2 C precision 0 5 C accuracy Closed loop temperature control Fully sea
16、lable 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 V
