Atomic Force Microscope (AFM)

Atomic force microscopy (AFM) is a method of measuring surface topography on a scale from angstroms to 100 microns. The technique involves imaging a sample through the use of a probe, or tip, with a radius of 20 nm. The tip is held several nanometers above the surface using a feedback mechanism that measures surface–tip interactions on the scale of nanoNewtons. Variations in tip height are recorded while the tip is scanned repeatedly across the sample, producing a topographic image of the surface.

In addition to basic AFM, the instrument in the Microscopy Suite is capable of producing images in a number of other modes, including tapping, magnetic force, electrical force, and pulsed force. In tapping mode, the tip is oscillated above the sample surface, and data may be collected from interactions with surface topography, stiffness, and adhesion. This results in an expanded number of image contrast methods compared to basic AFM. Magnetic force mode imaging utilizes a magnetic tip to enable the visualization of magnetic domains on the sample. In electrical force mode imaging a charged tip is used to locate and record variations in surface charge. In pulsed force mode (Witec), the sample is oscillated beneath the tip, and a series of pseudo force-distance curves are generated. This permits the separation of sample topography, stiffness, and adhesion values, producing three independent images, or three individual sets of data, simultaneously.

This instrument may also be used with a scanning tunnelling microscope (STM) head. STM utilizes quantum mechanical tunnelling of electrons to image conducting surfaces. 

ITG users may reserve time on the AFM using the AFM calendar.