Effect of the defects on the optical and electronic properties of plasma polymerized organic thin films

•Plasma polymerized thin films were grown by the PECVD using the cyclohexane as precursor.•The analysis reveals a highly disordered material.•A transition from a pure Csp3 precursor to a mainly Csp2 layer is observed.•Csp2 structures show a density of defects (with presence of odd rings).

The microstructure and electronic properties of plasma-polymerized thin films grown by the plasma enhanced chemical vapor deposition (PECVD) method using the cyclohexane as precursor gas are investigated as a function of the radiofrequency power. Infrared, Raman and optical transmission measurements, correlated with electron paramagnetic resonance ones, are applied to characterize the films in their as-deposited state. The results indicate that increasing the radiofrequency power induces a decrease of the total bonded hydrogen content, accompanied by an increase of the carbon C-sp2 hybridization proportion. A decrease of the optical gap, with increasing radiofrequency power also occurs, and might suggest an increasing overlapping of the Gaussian π–π* bands around the Fermi level. Simultaneously, an increase of the spin density is observed in the same range of the radiofrequency power, suggesting that most of the spins originate from C-sp2 complexes.