Question

Which statement is true for Scanning Tunneling Microscopy:

• A. Tunneling current between the surface and the probe
• B. Alternating current between the surface and the probe
• C. The electromagnetic radiation between the surface and the probe
• D. Direct current between the surface and the probe

Hint:

For STM, the keyword is "tunneling." Both its underlying principle and the quantity it measures are directly related to this quantum effect. STM measures the tunneling current.

Answer 1

The Correct Option is A

Step 1: Concept Overview:
The question focuses on the physical quantity measured or used to create an image in a Scanning Tunneling Microscope (STM).
Step 2: In-Depth Explanation:
As discussed earlier, STM relies on quantum tunneling of electrons between a sharp tip and the sample surface. This electron flow constitutes an electrical current known as the tunneling current.
The tunneling current's magnitude is highly sensitive to the tip-surface distance. The STM maintains a constant tunneling current by adjusting the tip height or measures current variations at a fixed height. In both scenarios, the tunneling current provides data about the surface's topography and electronic characteristics.
Options (B), (C), and (D) are incorrect. While the tunneling current is a direct current, "Tunneling current" accurately describes the measured phenomenon.
Step 3: Conclusion:
STM operation hinges on measuring the tunneling current between the surface and the probe.