Question

Identify the technique not typically associated with the top-down approach in creating nanoscale structures:

• A. Lithography
• B. Etching
• C. Self-assembly
• D. Milling

Hint:

Top-down: carve it. Bottom-up: grow it. Self-assembly builds from the bottom — not by cutting!

Answer 1

The Correct Option is C

Nanotechnology fabrication techniques are broadly categorized into two approaches: top-down and bottom-up.
The top-down approach involves starting with bulk materials and shaping them into nanoscale structures by removing material using physical or chemical processes. Common techniques include:

• Lithography: Patterning materials using light or electrons.
• Etching: Removing layers using chemical or plasma processes.
• Milling: Mechanical reduction of particle sizes or surface shaping.

Self-assembly, however, belongs to the bottom-up approach, where atoms or molecules organize themselves into structured arrangements due to physical or chemical interactions. It is driven by principles of thermodynamics and molecular affinity, not by external machining or fabrication steps. Therefore, self-assembly is not typically associated with the top-down approach.