Question

The top-down approach in nanofabrication refers to:

• A. Building structures atom-by-atom
• B. Assembling molecules using biological processes
• C. Carving or shaping materials into nanoscale structures
• D. Using chemical vapor deposition for coating

Hint:

The top-down approach in nanofabrication involves reducing the size of bulk materials into nanoscale dimensions. Techniques such as photolithography and etching are commonly used.
The bottom-up approach, on the other hand, builds structures by assembling atoms or molecules.
Understanding the distinction between these approaches helps in selecting the right method for fabricating nanoscale devices.

Answer 1

The Correct Option is C

To understand the top-down approach in nanofabrication, let's break down the concept and analyze each option.
Step 1: Understand nanofabrication
Nanofabrication is the process of designing and manufacturing devices and structures at the nanoscale. There are two primary approaches in nanofabrication: top-down and bottom-up. The top-down approach involves starting with larger, bulk materials and then carving or etching them into nanoscale structures. The bottom-up approach, in contrast, builds structures from atoms or molecules.
Step 2: Analyze Option A - Building structures atom-by-atom
Building structures atom-by-atom is characteristic of the bottom-up approach, where atoms and molecules are assembled to form nanostructures. This is not the top-down approach.
Thus, option A is incorrect.
Step 3: Analyze Option B - Assembling molecules using biological processes
Assembling molecules using biological processes is more closely related to biomanufacturing or biotechnology, which typically falls under bottom-up fabrication techniques. This is not a description of the top-down approach.
Thus, option B is incorrect.
Step 4: Analyze Option C - Carving or shaping materials into nanoscale structures
The top-down approach in nanofabrication involves carving, etching, or shaping larger materials into nanoscale structures. This approach uses techniques like photolithography, laser ablation, and etching to reduce the size of bulk materials to nanoscale dimensions.
Thus, option C is correct.
Step 5: Analyze Option D - Using chemical vapor deposition for coating
Chemical vapor deposition (CVD) is a technique used in both top-down and bottom-up approaches, but it specifically refers to the deposition of materials onto surfaces, not the shaping or carving of bulk materials into nanoscale structures. CVD is often associated with thin-film deposition and material coating.
Thus, option D is incorrect.
Step 6: Conclusion
The top-down approach in nanofabrication involves carving or shaping larger materials into nanoscale structures. This is best described by option C.