1. Scanning Tunneling Microscopy
Basics
Electron flow
A bias voltage needs to be applied:
Electron energy level densities
Transmission coefficient critically dependent on the
distance btw. tip & surf.
Conditions:
UHV but also air
Resolution:
typically,
0.1 nm lateral
0.01 nm depth

2. DVbias is necessary to raise the Fermi level and create free levels
for the electrons. Tunneling probability depends on the existence (and density) of free levels.
DVbias is positive or negative with reference to the tip’s Fermi level.

4. Basics of tunneling

7. Atomic Force Microsopy
Measurement of the surface roughness by the indirect attractive/repulsive effects on a nm-tip probe.
Ultimate resolution at atomic level (below 1 nm)
Lateral resolution depends on tip sharpness (see video&next)
Experiencing repulsive VdW (Pauli) forces
Experiencing attractive VdW forces (Sometimes combined with the oscillatory tapping mode, see next)
TYPICALLY:
(1) Contact AFM < 0.5 nm probe-surface separation (2) Intermittent contact (tapping mode AFM) nm probe-surface separation (3) Non-contact AFM nm probe-surface separation

8. AFM – Tapping mode Resolution depends on tip profile
The cantilever oscillation is slowed down (and amplitude increased) by attractive forces (larger distances)
and anhanced (and amplitude decreased) by attractive forces (shorter distances from surface)
Resolution depends on tip profile

9. Magnetic Force Microsopy
Typically used to get info on magnetic domains
Oscillation
Cantilever N S
Magnetic
interaction