AFM

Atomic Force Microscopy or AFM  is a technique allowing to visualise with a nanometric resolution the tridimensional morphology of a material surface, and map some of its properties (adhesives, mecanicals, magneticals, electricals, …).

The AFM principle is based on the interaction between the sample surface to analyse and a tip of nanometer scale sharpness, fixed under a cantilever. The tip  sweeps the surface and follows the sample topography, giving a tridimensional image of the analysed material.

The maximum area is 170×170 µm2 and the ultimum resolution is about one-tenth of a nanometre. This technique allows to observe surfaces in air or in liquid medium.
 

Applications

  • Analysis of all types of materials : polymers, biological samples, powders, metals, glass, …
  • Tridimensional morphological analysis
  • Roughness parameters measurements
  • Cartography of adhesives / viscoelastical properties
  • The maximum observable area is 170x170 µm2. To observe bigger areas or a larger clearance in z, we will prefer an optical profilometer.

How it works


Contact, Tapping, Peak Force Tapping, Peak Force QNM, Conductive AFM, Scanning Capacitance Microscopy
The AFM principle rely on the measurement of different interaction forces between atoms of the surface to observe and atoms of the tip. The working mode is chosen according to the information we want to obtain from the surface to analyse.

The topographical image can be coupled to mapping of certain phsical properties of materials:
  • Friction force , adhesive forces, elasticity modulus, dissipation
  • Magnetic power, electrostatics, conductivity, capacity
TESCAN ANALYTICS has also developed a stretching module to observe through AFM the evolution of polymer films morphology under a mechanical constraint.

AFM – Principal
AFM – Principal


The tip is fixed under a cantilever, of a determined stiffness. The sample is put on a piezoelectric ceramic material controling movings in the 3 directions X, Y, Z. When the sample is brought near the tip/sample, interaction forces tip/sample cause a deflection of the cantilever proportional to the force intensity. A laser beam, reflected on the back side of the cantilever and directed on a photodiode 4-quadrants, measures that deflection.

In the first historical mode, the  « contact mode », the deflection of the cantilever is maintained constant with a control loop while the sample is moved in X, Y and Z. A 3D topographical image is obtained.

 
AFM
AFM Image (topography) of Ti, 10µm x 10µm

Documents for download

ATOMIC FORCE MICROSCOPY
For more details about AFM download the more detailed PDF file!
pdf – 258 kB