Scanning Force Microscopy / Atomic Force Microscopy
The scanning or atomic force microscope SFM/AFM is a special type of scanning probe microscopy (SPM). It uses the mechanic forces between a surface and a sharp tip to image the surface with nanometer resolution. The surface is scanned with the tip which is adjusted on a cantilever. The mechanical deflection of the cantilever detected by a reflected laser beam delivers the height of each point of the surface. From the height values of all points, a topography image of the surface is constructed. With a special conductive tip additionally charges on the surface can be imaged (electric force microscopy EFM). A similar contactless method to image surfaces on the micrometer scale ist the MicroGlider.
On the other hand, the SFM is used to measure directly the interaction forces between a surface and an AFM tip or a colloidal particle attached to a cantilever (colloid probe technique). In various modes, different kinds of forces (mechanical, electrostatical, magnetical, chemical interactions) are accessible. Both vertical and lateral (friction) forces can be determined with spatial resolution (force volume mode, lateral force microscopy LFM). With a special setup the Micro-thermal Analysis (µTA), a local thermal analysis at interfaces can be performed.
In our surface forces lab, three SFM devices are available in a climatized clean-room environment:
- Multimode / Nanoscope III, Multimode (Digital Instruments)
- Dimension 3100 / Nanoscope III (Digital Instruments)
- Dimension 3100 / Nanoscope IV (Digital Instruments)
The Multimode AFM allows to investigate samples with a size of up to 1x1cm². An area of maximum 50x50µm² size can be imaged. The Multimode SFM can be run in an environmental chamber under defined environmental conditions (temperature, humidity, composition of the atmosphere) as well as with a closed liquid cell and a heating stage to enable imaging or force measurements in liquids or at elevated temperatures.
In the Dimension AFMs, larger samples can be used. They are equipped with open fluid cells.