Force Curves
42
Scanning Probe Microscope Training Notebook
Rev. F
17.0 Force Curves
Force curves are commonly used to set the imaging force in contact mode and to study attractive,
repulsive, and adhesive interactions between the tip and the sample.
The Realtime menu for obtaining force curves is found under
View
>
Force
Mode
>
Calibrate
.
When a force curve is acquired, the lateral (X and Y) movement of the scanner is stopped, and the
scanner extends and retracts the Z electrode of the scanner.
•
For the MultiMode AFM, the sample is moved with respect to a stationary tip, and with
the Dimension and BioScope AFMs, the tip is moved with respect to a stationary
sample.
A force curve plots the deflection of the cantilever as it contacts and separates from the sample
during the extension and retraction of the scanner.
Figure 17.0a
Typical Force Curve with Schematic Labeling Corresponding Tip-Sample Interaction Points
On the force curve graph, the distance of the scanner movement is represented by the
horizontal
axis, and the cantilever deflection is represented by the
vertical
axis.
Primary parameters for obtaining a force curve include:
•
Z-scan start
: Defines the starting point of the scanner movement within the overall Z
scan range.
•
Ramp size:
Vertical scanner movement distance.
•
Setpoint:
Used to set the imaging force. This is the same parameter as the
Setpoint
in
Image Mode
.
A
B
C
D
E
Approach
Jump to contact
Contact
Adhesion
Pull-off
