The Dimension 3100 atomic force microscope (Bruker) can map the topography of a sample’s surface, as well as certain physical and mechanical properties, with fields of view ranging from 30 µm to a few tens of nanometers.
Several modes available: tapping, contact, EFM, MFM.
Accessories: cell for experiments in liquid media, anti-vibration housing, backlit sample holder for thin standard slides.
- Contact mode. The tip remains in contact with the sample at all times during the scan, the vertical deflection is kept constant and the z-displacement of the lever therefore provides a direct image of the topography of the sample surface (the horizontal deflection then provides information on the friction between the tip and the surface). This mode also offers the possibility of producing point approach-shrinkage curves, which can be used to determine certain properties locally (inelastic and elastic deformations, adhesion force between tip and surface, etc.). Its main drawback is the rapid degradation of fragile samples/tips, and the resulting artifacts.
- Tapping mode. The tip oscillates at the microlever’s resonant frequency, and is therefore only in intermittent contact with the surface. The topography of the sample can therefore be imaged with minimum degradation; the phase delay (error signal) also provides information on viscoelasticity contrasts.
- MFM mode. The magnetized tip oscillates at the microlever’s resonant frequency and scans the surface of a magnetic sample at constant altitude (non-contact mode). Frequency modulations caused by magnetic tip/surface interactions can then be used to map local magnetic field variations.
Principle of analysis :
An atomic force microscope essentially consists of a very fine tip fixed under a micrometric lever arm; when this lever scans the surface of a sample, measuring its deflection maps the surface topography and gives access to some of its physical and mechanical properties.
Lateral resolution: depends on the nature of the sample and the type/radius of curvature of the tip.