Crystal Growth Control of Functional Oxide Thin Films on Nanopatterned Substrate Surfaces

A straight nanogroove striped pattern can be formed on the surface of NiO thin film by room temperature epitaxial growth in pulsed laser deposition (PLD) on a 0.2 nm-high regularly stepped sapphire (alpha-Al2O3 single crystal) (0001) substrate and post annealing of the film. The interval and depth of each nanogroove were about 80 and 20nm, respectively. Wedge shaped nanogrooves were observed on the entire film (similar to 10 x 10 mm(2)) and characterized on an atomic scale by high resolution transmission electron microscope (TEM). Using the nanogrooved NiO thin film or atomically stepped sapphire substrate as thermal nanoimprint mold for glass, surface nanopatterning of the silicate glass plate was successfully carried out. The straight nanogroove pattern or sub-nanometer stepped pattern were inversely transferred onto the glass surface. Growth control of transparent conducting indium tin oxide (ITO) thin films was then examined on the nanoscale step-patterned glass plates by PLD. The surface morphology of the obtained ITO thin films reflected the stepped pattern of the glass plate well. Strongly oriented film growth was achieved on the nanopatterned glass. The resistivity of ITO thin film deposited on the nanoimprinted glass was lower than that of the film on the commercial glass.