Structural and optical properties of plasma polymerized o-methoxyaniline thin films

Plasma polymerized o-methoxyaniline (PPOMA) thin films of different thicknesses were prepared in glow discharge plasma using a parallel plate capacitively coupled polymerization reactor. The PPOMA thin films are smooth, flawless and pinhole free. Fourier transform infrared spectra reveal a decrease of absorption intensity and disappearance of some absorption peaks for PPOMA as compared to those of OMA, indicating the formation of the thin film with modified/changed chemical structure. Analyses of the ultraviolet–visible spectroscopic results reveal that the allowed indirect (Egi) and direct (Egd) band gap energies have values in the range 1.68 to 2.08 eV and 2.90 to 3.08 eV, respectively for PPOMA thin films of thicknesses from 100 to 300 nm. The Egi of the experimental PPOMA thin films does not show any definite trend with film thickness, whereas the Egd shows weak dependence on film thickness.

► Plasma polymerization method used to prepare poly o-methoxyaniline thin films.
► Films are smooth and flawless and have elemental similarities with the monomer.
► Fourier transform infrared spectra confirmed the films' modified chemical structure.
► Allowed indirect transition band gap is in the range 1.68 to 2.08 eV.
► Allowed direct transition band gap is in the range 2.90 to 3.08 eV.