Effect of distance from discharge to substrate on plasma-polymerized polythiophenes

•We prepared conducting polymers with a mid-frequency plasma at various distances.•We found that the film's conductivity increased with distance up to 110 mm.•Conductivity increase appears due to better chain–chain packing induced by gas-phase nucleation and growth.

Plasma-polymerized polythiophenes were deposited as thin films utilizing plasma of mid-range frequency (40 kHz) and low power (4 W). The thin films were prepared by changing the distance from the top electrode to the substrates, and the resulting films were compared. Conductivity increased with distance up to 110 mm, and then decreased with further increase in distance. FT-IR and XPS analysis showed that the thin films had similar molecular structures regardless of the distance. However, as the distance increased, surface roughness increased from 0.54 to 5.53 nm, which suggested gas-phase nucleation and molecular packing.