Atomic Force Microscopy

Atomic Force Microscopy (AFM) is a high-resolution scanning probe imaging method. The basic AFM working principle is the measurement of the interaction force between a tip and the sample surface using special probes made by an elastic cantilever (silicon or silicon nitride) with a sharp tip (radius of curvature about 10 nm) on the end. The deflection of the cantilever is measured by laser spot reflected from the cantilever surface into the array of photodiodes. AFM operates in three different modes:

• Contact mode – for hard samples with flat surface
• Semi contact (tapping) mode – wide spectra of samples including polymers
• Non contact mode – soft samples

Figure 1: AFM working principle.

 

Generally, the tapping mode is mostly used, because it does not damage the sample surface during the scanning as the contact mode does and with good adjustment the results are without any artifacts in the contrary to the non contact mode. Our AFM is a model Ntegra from NT MDT. The main advantage of AFM in comparison with other techniques:

• high resolution (almost “atomic”),
• scanning the samples in their native states (air or liquid environment),
• 3D sample surface profile,
• no special sample treatment (i.e., no coating required),
• good contrast between the individual phases in the multi phase morphology.