Atomic Force Microscopy (AFM)
AFM is an advanced form of stylus profilometry where an extremely sharp inert tip is scanned over a surface to produce topographical images. When the atoms at the end of the tip approach those on a surface there is an initial attractive force which becomes repulsive as they touch. The force of penetration into the sample is a measure of the local hardness.
In the normal contact mode, the tip is mounted at the end of a delicate flexible cantilever which is deflected as the tip is rastered over the surface. The deflection is measured using a laser reflected off the back of cantilever and its movement monitored by a quadrant of photocells. In this mode, the tip also suffers drag due to friction which causes the cantilever to twist as well as bend, thereby enabling both the frictional force and topography to be monitored.
By oscillating the cantilever at its resonant frequency and measuring how this changes when influenced by the attractive force as the tip repeatedly taps the surface, a non-contact mode becomes available for topographical imaging where tip wear is greatly reduced.
There are many variants of AFM which are all capable of imaging features that are too small to be seen in conventional optical microscopes and so normally require SEM analysis. AFM however can be carried out in air or under liquids with minimal sample preparation and where provision of topographical measurements such as roughness parameters is facilitated.
- Imaging sub-micron features at nm resolution
- Quantitative topographical measurements
- Relative hardness imaging
- Friction distribution imaging.
- Surface roughness measurements
- Atomic level surface modification
- Material defects.
Typical Industries using AFM
- Medical devices
Atomic Force Microscopy - At a Glance
- Information: Images of surface topography, friction distribution, hardness variation
- Sampling Depth: Outermost surface
- Area Analysed: 10µ x 10µ rasters
- Maximum Sample Size: 20mm diameter x 15mm thick
- Data Output: Contact or non-contact mode surface images, roughness/hardness/modulus parameters