1. Scanning Probe Microscopy
Introduction and Atomic Force Microscopy

2. SPM (Scanning Probe Microscopy)
SPM: Consists of a family of microscopy forms where a sharp probe is scanned across a surface and probe/sample interaction is monitored.
Two primary forms of SPM:
Scanning Tunneling Microscopy
Atomic Force Microscopy (AFM):
contact mode
non-contact mode
tapping mode

3. Atomic Force Microscopy - Introduction
In simple terms, the atomic force microscope works by scanning a sharp probe over the surface of a sample in a raster pattern. By monitoring the movement of the probe, a 3-D image of the surface can be constructed.
The schematic is shown to the right
Figure 4. Three common types of AFM tip. (a) normal tip (3 µm tall); (b) supertip; (c) Ultralever (also 3 µm tall). Electron micrographs by Jean-Paul Revel, Caltech. Tips from Park Scientific Instruments; supertip made by Jean-Paul Revel.

4. Atomic Force Microscopy -Tip – Surface Interaction
The combination of these interactions results in a force-distance curve similar to that below
When the tip is brought close to the sample, a number of forces may operate.
Typically the forces contributing most to the movement of an AFM cantilever are the coulombic and van der Waals interactions.
Coulombic Interaction: This strong, short range repulsive force arises from electrostatic repulsion by the electron clouds of the tip and sample. This repulsion increases as the separation decreases.
Van der Waals interactions: These are longer range attractive forces, which may be felt at separations of up to 10 nm or more. They arise due to temporary fluctuating dipoles.

5. Atomic Force Microscopy - Topography
Contact Mode
High resolution
Damage to sample
Can measure frictional forces
Non-Contact Mode
Lower resolution
No damage to sample
Tapping Mode
Better resolution
Minimal damage to sample
2.5 x 2.5 nm simultaneous topographic and friction image of highly oriented pyrolytic graphic (HOPG). The bumps represent the topographic atomic corrugation, while the coloring reflects the lateral forces on the tip. The scan direction was right to left