Tunneling Effect:

Principle: Tunneling
The tunneling current is expressed by

Energy Diagram:

Figure 20.06: Schematic of tip and sample surface for tunneling process.

Comments:

1. A slight change of distance between the tip and sample surface as shown in Figure 20.06 causes the current to decrease exponentially. For example: in the case I = 2 nA, V = 100 mV, d = 0.7nm; when d decreases by 0.1 nm (15% lower), V is set constant, then one achieves I = 10 nA (4 times greater).

2. If one measures the tunnel current accurately, a detection of tiny variation of the distance in the atomic scale would be easily possible.