Device performance and polymer layer morphology in polymer bistable device (PBD): the control of physicochemical...

The surface morphology control of poly(N-vinyl carbazole) (PVK) layer for the improvement of polymer bistable devices (PBDs) performance was investigated based on the simultaneous consideration of the compatibility of polymer with solvent and the polymer ordering behavior during the solvent evaporation by introducing the bisolvent system of chloroform and 1,1,2,2-tetrachloro-ethane (TCE). It was confirmed by ultra violet (UV)-vis spectroscopy that PVK has significantly higher compatibility with chloroform than TCE. On the other hand, atomic force microscope (AFM) revealed that the chloroform/TCE = 9/1 bisolvent led to the improved film morphology (the surface roughness of 0.190 nm) than chloroform, because the presence of TCE representing slower evaporation rate contributed to the enhancement of PVK ordering and arrangement during the solvent evaporation for the film formation. The great correlation was made between the film morphology properties and I-V characteristics of PBDs. The PBDs with PVK layer cast from the chloroform/TCE = 9/1 bisolvent showed dramatically improved bistability characteristics (Vth approximately equal to 2 V and Ion/Ioff ratio > 10(3)).