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We are using an OMICRON AFM to investigate surfaces at nanoscale in UHV. The AFM is a very high resolution type of scanning probe microscope for imaging, measuring and manipulating matter. The AFM consists of a cantilever with a low spring constant, providing a sharp tip at its end which is used to scan the sample surface, an IR-laser aligned with the cantilever and a deflection sensor which is a four-quadrant-photodiode.

The tip of the cantilever is scanning the surface, reacting in response to the forces between the tip and the sample surface. A laser focused on the back of the cantilever and reflected onto a split photo-diode makes the smallest responses of the tip visible. By keeping track of changes in signal, the bending of the cantilever due to the interaction with the surface can be measured and the forces bending the cantilever can easily be derived, given a known spring constant of the cantilever. Obtaining data by this simple method, the image displays the surface in all three dimensions without the limit of optical diffraction in contrast to optical microscopes - thus resolutions several nm (in ambient conditions) or even atomic resolution (in UHV conditions) are possible.

Atomic Force Microscopy concept: a laser is reflected off the back of a cantilever on a split photo diode

Investigations can either be performed on any flat surface in air or in Vakuum. Several operational modes are possible, the most common ones are CONTACT MODE and TAPPING MODE, enabling a wide approach for measuring various effects on surfaces - like roughness, local magnetic properties, defects induced by radiation or toughness. Since the cantilever is barely in contact with the surfaces, or even not even touching it at all (non-contact mode), the AFM provides a versatile, non destructive tool for investigation.
Internal view of UHV chamber with sample carousel in front and the AFM stage at the back - access to the chamber is only possible via manipulator

 AFM tip as seen through magnifying optics on a screen - the glow of an infrared laser is visible as bright, white spot beneath the barely visible tips

The OMICRON AFM is a high resolution tool that may provide investigations of atomic resolution. The vacuum chamber also features a heating stage for sample preparation and a transfer chamber for extracting/adding samples to the main chamber without having to ventilate it.

For further information please contact:
* Prof. Dr. Aumayr Friedrich ([email address: lastname @ this server · enable javascript to see it])
* Ritter Robert ([email address: lastname @ this server · enable javascript to see it])
* Vasko Christopher ([email address: lastname @ this server · enable javascript to see it])

atomic/instrumentation/uhv-afm.txt · Last modified: 2009-06-09 17:50 by vasko