Publications by authors named "Nam-Goo Cha"

A novel nanofabrication technique is developed for functional oxides. Combining nano-imprint lithography, sidewall-etching and sidewall-deposition processes enables us to prepare Mo hollow nanopillar masks with 100 and 60 nm window sizes, which is smaller than the original nano-imprint mold size of 250 nm. Using this Mo nanomask, extremely small epitaxial ferromagnetic oxide (Fe(2.

View Article and Find Full Text PDF

Methacrylate octafunctionalized silsesquioxane (SSQMA) was shown to be an ideal material with high performance for ultraviolet (UV)-based nanoimprint lithography (NIL). The total viscosity of SSQMA-based formulations was adjusted to between 0.8 and 50 cP by incorporating low-viscosity acrylic additives, making the formulations suitable for UV-based NIL.

View Article and Find Full Text PDF

This paper provides a unique strategy for controlling integrated hollow nanostructure arrays such as boxes or pillars at the nanometer scale. The key merit of this technique is that it can overcome resolution limits by sidewall deposition and deposit various materials using a sputtering method. The sputtering method can be replaced by other dry deposition techniques such as pulsed laser deposition (PLD) for complex functional materials.

View Article and Find Full Text PDF

A convective directed-assembly process on a flat substrate that does not require motion and is followed by a dry-transfer process of nanoparticles is presented. The convective assembly process was achieved using Au nanoparticles on hydrophobic/hydrophilic-surface-patterned Si substrates as functions of temperature, gap height, and particle size. An investigation of the particle assembly mechanism showed that the effects of temperature, gap height, and particle size were responsible for controlling the evaporation time, the evaporation length, and the assembly speed, respectively.

View Article and Find Full Text PDF

Two-dimensional (2-D) and three-dimensional (3-D) diamond-like carbon (DLC) stamps for ultraviolet nanoimprint lithography were fabricated with two methods: namely, a DLC coating process, followed by focused ion beam lithography; and two-photon polymerization patterning, followed by nanoscale-thick DLC coating. We used focused ion beam lithography to fabricate 70 nm deep lines with a width of 100 nm, as well as 70 nm deep lines with a width of 150 nm, on 100 nm thick DLC layers coated on quartz substrates. We also used two-photon polymerization patterning and a DLC coating process to successfully fabricate 200 nm wide lines, as well as 3-D rings with a diameter of 1.

View Article and Find Full Text PDF