Fabrication and Characterization of Electronic and Optical Properties of Polyaniline Nanopatterns

The authors conducted polyaniline (PA) polymerization on a micro-scale patterned Si wafer and nano-scale patterned Al surface. Polymerization was performed using a microliter solution droplet made of aniline, HCl and oxidation agent ammonium peroxodisulfate (APS). The droplet was dropped on a flat Si wafer, a micro-patterned Si wafer and a nanostructured Al surface. The SEM image showed that PA was densely polymerized on the circle edge of the dropped 1 mm sized droplet on the flat Si wafer because of large surface tension due to the flat surface. On the other hand, a droplet was broken on a circular trench pattern of 100 μm in diameter fabricated on a Si wafer. The width and depth of the trench were 1 μm and 1 μm, respectively. Tree-like polymer was intensively polymerized along the circular trench. Droplet was also dropped on a lattice trench pattern whose pitch was 10 μm. The width and the depth of the trench were 1 μm and 1 μm, respectively. The SEM image showed that dots of PA were fabricated along the trenches. Far smaller dots of PA were also observed on the flat area of the lattice. Thus, micro-scale structure affects the shape and size of PA in polymerization. Nanoscopic polymerization of PA was conducted locally in a nanoscale highly-oriented line pattern with nanoscale trenches formed on an Al surface. One of the characteristic fabricated patterns was a highly conductive PA line pattern whose pitch was 100 nm. In this case, point-contact IV characteristic measurement, step-like curve was observed. PL spectra of the PA line-pattern exhibited significantly enhanced emission peaks at 380, 450 and 550 nm due to PA which were overlapped by the rippled PL pattern due to the Al nanostructure.