Plasma-enhanced chemical vapor deposition of polyperinaphthalene thin films

Plasma-enhanced chemical vapor deposition (PECVD) has been used to grow corrosion-resistive, semiconducting thin films of the graphite-like polymer polyperinaphthalene (PPN) from 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA). Unlike thermal chemical vapor deposition of PPN from PTCDA, where thin film growth is catalyzed by a transition metal substrate, PPN films have been grown by PECVD for the first time on non-catalytic substrates: indium tin oxide (ITO)-coated glass, aluminum and silicon. Films with the same morphology and molecular characteristics have also been grown on steel substrates, where iron functions as a growth catalyst. Potentiodynamic corrosion measurements in pH 5 water show that PPN films on steel provide an effective corrosion protection layer. Plasma deposition parameters and electrical conductivities of the films on different substrates have been determined together with their nanoscale morphology and chemical structure using scanning electron microscopy, and Raman and Fourier transform infrared spectroscopy, respectively. These results suggest that under plasma conditions at a substrate temperature of 450 °C, a large fraction of the anhydride groups in PTCDA are eliminated without decomposition of the perylene backbone. The perylene and perylenedicarboxylic radicals adsorb on the substrate and undergo plasma-enhanced polymerization to form partially cross-linked PPN thin films.