Question

Scanning Tunneling Microscopy is based on:

• A. Classical -mechanical phenomenon
• B. Quantum -mechanical phenomenon
• C. Mechanical Phenomenon
• D. Classical phenomenon

Hint:

The word "Tunneling" in Scanning Tunneling Microscopy is the biggest clue. Tunneling is a hallmark phenomenon of quantum mechanics that has no classical analogue.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Scanning Tunneling Microscopy (STM) is a powerful technique for imaging surfaces at the atomic level. Its working principle relies on a unique physical effect.
Step 2: Detailed Explanation:
The operation of an STM involves bringing an atomically sharp conducting tip extremely close (a few angstroms) to a conducting or semiconducting surface. A small voltage bias is applied between the tip and the surface.
According to classical physics, electrons do not have enough energy to overcome the potential barrier of the vacuum gap between the tip and the surface, so no current should flow.
However, due to the principles of quantum mechanics, electrons have a wave-like nature. Their wave function does not drop to zero at the barrier but decays exponentially into it. If the barrier (the gap) is thin enough, there is a finite probability that an electron can pass through the barrier and appear on the other side. This effect is known as quantum tunneling.
The flow of these tunneling electrons constitutes a measurable current, which is extremely sensitive to the tip-surface distance. The STM uses this tunneling current to map the topography of the surface.
Step 3: Final Answer:
The fundamental principle behind Scanning Tunneling Microscopy is the quantum-mechanical phenomenon of electron tunneling.