Model: EFM-2017

Download EFM Datasheet

In EFM, a conductive cantilever tip is used an sample is prepared with surface potentials on it is needed. The tip and sample are separated a distance z usually by air or vacuum. A bias voltage between tip and sample is applied by an external voltage supply that forming a capacitor, C, between tip and sample. The capacitance of the system depends on the geometry of the tip and sample. The total energy stored in that capacitor is U = 1/2C*ΔV^2. The w ork done by the voltage supply to maintain a constant voltage, ΔV, between the capacitor plates (tip and sample) is -2C*U. The z component of the force (the force along the axis connecting the tip and sample) is thus:

When the tip scans the surface of a sample at close distances (< 5 nm), not only long range electrostatic forces are sensed, but also van der Waals force, atomic interaction forces. In order to reduce topography artifact in the EFM image, a second path of scan at lifted distance from the surface topography is implemented. The commercial implementation of this method is so-called “Lifting” method.