Top-Down fabrication involves starting with a bulk material and then etching or milling it down to the desired nanoscale structure. This technique is akin to sculpting a statue from a large block of marble. Common methods include Photolithography and Electron-Beam Lithography.
Photolithography Photolithography is widely used in the semiconductor industry. It involves transferring a pattern from a mask to the surface of a substrate by exposing it to light. This technique is highly effective for patterning at the micro and nanoscales but has limitations in achieving the smallest dimensions due to the diffraction limit of light.
Electron-Beam Lithography Electron-Beam Lithography (EBL) uses a focused beam of electrons to create very fine patterns on a substrate. EBL can achieve higher resolution than photolithography, making it suitable for fabricating features at the nanoscale. However, it is a slower and more expensive process, often used for research and prototyping rather than mass production.
