Ultra-flat and Ultra-small: Towards Atomic-Resolution Engineering of Metallic Nanostructures

This presentation will cover two unconventional nanofabrication techniques, namely, template stripping for making atomically smooth patterned metals [1-2] and atomic layer lithography for mass-producing sub-10 nm gaps [3-4]. These ‘enabling’ technologies have benefitted numerous applications in nanosciences, and we will show some examples.

Template stripping is widely used to create ultra-smooth metal films, plasmonic gratings, waveguides, high-Q resonators, and ultra-sharp pyramidal tips for near-field optical spectroscopy. In this unconventional process, instead of directly patterning metal films, which are difficult to plasma-etch, we engineer inverse patterns in a silicon template using mature IC processing techniques. After metal deposition and peeling, ultra-smooth patterns in the silicon template are replicated onto the deposited metal film. I will discuss applications of template-stripped metal films for near-field optical spectroscopy, plasmonics, and 2D materials.

Our group has demonstrated a new technique called atomic layer lithography [3-4], which leverages Angstrom-scale thickness resolution of atomic layer deposition to pattern equally small gaps and slits in metal films. Using this new method, we have demonstrated wafer-scale production of ultra-long (up to centimeters) and sub-10-nm wide gaps in various metals. The resulting devices have been used for a wide range of optical and electrical experiments, including extraordinary optical transmission through single-nanometer gaps, optical trapping of protein molecules, and surface-enhanced spectroscopies, to name a few. I will present broader potential applications of this technology.