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10/27/14
Atomic Force Microscope Vecco Dimension 3100
(supported by Bruker)
Location White Bldg.
Room 613
10/27/14 Atomic Force Microscope
AFM Control unit and software Atomic Force Microscope
10/27/14 Atomic Force Microscope Components
(S)canning (P)robe (M)icroscope head Stage holder and (2) types of tips 1. Tapping 2. Contact 3. Magnetic (not shown)
10/27/14
Atomic Force Microscope Tips
Tapping tip on holder.
Zoom in on tip.
www.brukerafmprobes.com
Typical Silicon Tips 5-20 nm tip radii 20-100 N/m stiffness
10/27/14 Atomic Force Microscope Tips
Contact tip on holder.
Zoom in on tip.
www.brukerafmprobes.com
Important to match the stiffness of the tip to the sample being measured.
10/27/14 Atomic Force Microscope Simplistic Operation Click to play
10/27/14 Example of AFM measurements – Tapping Mode
Nanoindentation – Optical image
Nitinol material
10/27/14 AFM scan - 30 um x 30 um
Nitinol material – Limitations of scan 100 um x 4.8 um deep
10/27/14 AFM scan - 30 um x 30 um – isometric
Nitinol material
10/27/14 AFM Geometry Analysis
Nitinol material
10/27/14 AFM Geometry Analysis – Vertical Distance
Nitinol material
10/27/14 AFM Geometry Analysis – Rmax
Nitinol material
10/27/14 AFM Geometry Analysis – Depth of indent
Nitinol material
9/9/14 AFM Geometry Analysis – Angle of indent
Nitinol material
10/27/14 Picking the right AFM Tip – Size matters
Click to play
10/27/14
Understanding contamination and its effects Click to play
• In ambient air, surface are covered with contamination • A probe encounters contamination when approaching a surface • Capillary forces pull the contamination up onto the probe
Contact AFM – Force Microscopy
10/27/14 Using contact mode with Force modulation
Consider a simple case of Tip / Sample interaction
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0
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Def
lect
ion
(nm
)
Extension (nm)
Extend
Retract
The X & Y of the scanner is fixed. It moves in Z as shown by Extension.
Rubber sample material
A
Van der Waals forces can be seen as the tip approaches the surface (A).
10/27/14 Tip / Sample interaction
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0
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Def
lect
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(nm
)
Extension (nm)
Extend
Retract
These attractive forces pull the tip down.
Rubber sample material
B Point of contact (B).
A
10/27/14 Tip / Sample interaction
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0
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Def
lect
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(nm
)
Extension (nm)
Extend
Retract
Extension continues and the cantilever bends upward.
Rubber sample material
B
C
Until (C), where the extension stops and so does the deflection.
Point of contact (B).
10/27/14 Tip / Sample interaction
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0
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Def
lect
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(nm
)
Extension (nm)
Extend
Retract
C – As the scanner retracts, the deflection decreases (C to D) – red curve. The cantilever relaxes.
Rubber sample material
D
C
There may be surface attraction between the tip and sample which keeps the tip in contact with the surface. A monolayer of water can also provide this attraction.
10/27/14 Tip / Sample interaction
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Def
lect
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(nm
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Extension (nm)
Extend
Retract
E – As this force is overcome, the tip snaps quickly back as shown from by the vertical trajectory from D to E.
Rubber sample material
D
E
10/27/14 Tip / Sample interaction
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0
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0 500 1000 1500 2000 2500
Def
lect
ion
(nm
)
Extension (nm)
Extend
Retract
Force Curve Summary
Rubber sample material
D
E
A
B
C
Magnetic Force Microscopy Magnetic force microscopy (MFM) scans are performed using a resonating Co-coated tip on the Bruker Dimension 3100 atomic force microscope. Two scans are made over the same area.
The first scan determines the topology of the surface.
The second scan is done at a fixed height (200 nm) above the surface. Any changes in the phase of resonance of the tip are due to the magnetic field of the specimen.
10/27/14
MFM Cross-Sectional Image of a Carburized Duplex 2205 Stainless Steel
surface
g 20 mm
Magnetic Ferrite
Nonmagnetic Austenite: the carbon at the surface prevents polishing-induced martensite
Austenite with some polishing-induced Surface Martensite (which is magnetic)
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10/27/14
Thank you
