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Get to the point!
Get to the point!
AFM - atomic force microscopyAFM - atomic force microscopy
A 'new' view of structure (1986)A 'new' view of structure (1986)
AlGaN/GaN quantum well waveguideAlGaN/GaN quantum well waveguide
CD stamperCD stamper
polymer growthpolymer growth
surface atoms on Si single crystalsurface atoms on Si single crystal
See Vocabulary of Surface Crystallography, Journal of Applied Physics 35, 1306 (1964), by Elizabeth A. Wood
AFM - atomic force microscopyAFM - atomic force microscopy
How does the microscope work?How does the microscope work?
Si3N4
tip
Si3N4
tip
laserdiodelaserdiode
photodiodephotodiode
samplesample
mirrormirror
Tip scans sample
Up and down movement of tip recorded by position sensing photodiode
Tip scans sample
Up and down movement of tip recorded by position sensing photodiode
AFM - atomic force microscopyAFM - atomic force microscopy
How does the microscope work?How does the microscope work?
Si3N4
tip
Si3N4
tip
laserdiodelaserdiode
photodiodephotodiode
samplesample
mirrormirror
Tip scans sample
Up and down movement of tip recorded by position sensing photodiode
Tip scans sample
Up and down movement of tip recorded by position sensing photodiode
AFM - atomic force microscopyAFM - atomic force microscopy
How does the microscope work?How does the microscope work?
Si3N4
tip
Si3N4
tip
laserdiodelaserdiode
photodiodephotodiode
samplesample
mirrormirror
Two modes of operationTwo modes of operation
AFM - atomic force microscopyAFM - atomic force microscopy
How does the microscope work?How does the microscope work?
Contact mode - short-range interactions (Å) - interatomic forcesContact mode - short-range interactions (Å) - interatomic forces
Tip: 5-20 nm radius, 10-25 m high, on 50-400 m cantilever beam
Tip: 5-20 nm radius, 10-25 m high, on 50-400 m cantilever beam
AFM - atomic force microscopyAFM - atomic force microscopy
How does the microscope work?How does the microscope work?
Detector system can measure deflections in nm range
Detector system can measure deflections in nm range
Tip: 5-20 nm radius, 10-25 m high, on 50-400 m cantilever beam
Cantilever: low stiffness - can't deform surface
Tip contacts surface
Tip scans surface: either tip or specimen moved by piezoelectric positioning system over x and y
Tip: 5-20 nm radius, 10-25 m high, on 50-400 m cantilever beam
Cantilever: low stiffness - can't deform surface
Tip contacts surface
Tip scans surface: either tip or specimen moved by piezoelectric positioning system over x and y
Contact mode - short-range interactions (Å) - interatomic forcesContact mode - short-range interactions (Å) - interatomic forces
AFM - atomic force microscopyAFM - atomic force microscopy
How does the microscope work?How does the microscope work?
Contact mode - short-range interactions (Å) - interatomic forces
Two ways - 'constant force' ……. feedback system moves tip in z direction to keep force constant
'constant height'……. no feedback system -
usually used when surface roughness small
higher scan speeds possible
Contact mode - short-range interactions (Å) - interatomic forces
Two ways - 'constant force' ……. feedback system moves tip in z direction to keep force constant
'constant height'……. no feedback system -
usually used when surface roughness small
higher scan speeds possible
AFM - atomic force microscopyAFM - atomic force microscopy
How does the microscope work?How does the microscope work?
Tapping mode - long-range forces - van der Waals, electrostatic, magnetic
Tapping mode - long-range forces - van der Waals, electrostatic, magnetic
Tip vibrates (105 Hz) close to specimen surface (50-150 Å) with amplitude 10-100 nm
May at times lightly contact surface
Tip vibrates (105 Hz) close to specimen surface (50-150 Å) with amplitude 10-100 nm
May at times lightly contact surface
Suitable for soft materialsSuitable for soft materials
AFM - atomic force microscopyAFM - atomic force microscopy
How does the microscope work?How does the microscope work?
Tapping modeTapping mode
Tip vibrates (105 Hz) close to specimen surface (50-150 Å) with amplitude 10-100 nm
May at times lightly contact surface
When near or on surface, oscillation is damped - tip z position corrected so that vibration amplitude stays constant
Tip vibrates (105 Hz) close to specimen surface (50-150 Å) with amplitude 10-100 nm
May at times lightly contact surface
When near or on surface, oscillation is damped - tip z position corrected so that vibration amplitude stays constant
Tip height
Am
plit
ude
AFM - atomic force microscopyAFM - atomic force microscopy
From force-distance plot, can get:range & magnitude of attractive & repulsive forceselastic modulus & adhesion energy
From force-distance plot, can get:range & magnitude of attractive & repulsive forceselastic modulus & adhesion energy