Figure 2. Electronic energy band line-up for a metallic tip-semiconductor system when the tip and the back surface of the semiconductor are electrically connected.
The contact potential difference VCPD depends on the tip work function ϕtip, on the electron affinity of the semiconductor χ, as well as on the difference between the bottom energy level of the conduction band Ec and the Fermi level EF in the semiconductor. In this case, the effect of the surface band bending ϕB is included in the bulk.