Scanning Probe Microscopy: Principles

All of the techniques are based upon scanning a probe just above a surface whilst monitoring some interaction between the probe and the surface (see Figure 20.03).

Figure 20.03: Schematic of SPM principle.

The interaction that is monitored in:

• STM works on the tunneling current between a metallic tip and a conducting substrate which are in very close proximity but not actually in physical contact.

• AFM works on the principle of Van der Waals forces between the tip and the surface as discussed in last lecture; this may be either the short range repulsive force (in contact-mode) or the longer range attractive force (in non-contact mode).