Insights into the structural and optical features of plasma polymerized N, N, 3, 5 tetramethylaniline-2,6-diethylaniline thin films

Abstract

A capacitively coupled AC (50 Hz) glow plasma has been used to produce plasma polymerized N, N, 3, 5 tetramethylaniline: 2,6-Diethylaniline composite thin films onto precleaned glass substrates at various monomer ratios. The FSEM studies revealed smooth, compact, flawless, and pinhole-free surfaces of the thin films. The energy-dispersive X-ray spectrum confirmed the existence of carbon, nitrogen, and oxygen in the composite thin films. The broadband weak absorption peaks in the FTIR spectra indicated the structural modifications in the plasma polymer caused by the reorganization of two monomer molecules during the plasma polymerization process. The thickness of the composite film increased with rising N, N, 3, 5 tetramethylaniline percentage in the composition, which had an important effect on the optical properties while keeping the polymerization parameter the same for all the deposited films. Decreasing the proportion of N, N, 3, 5 tetramethylaniline monomer results in an increase in both direct and indirect optical band-gap values, from 2.84 to 2.94 eV and 1.74–1.87 eV, respectively. While the Urbach energy values decrease from 0.649 eV to 0.556 eV. From the optical absorbance curve, it was observed that with increasing N, N, 3, 5 tetramethylaniline monomer concentration, the absorbance increased and reached a maximum at this monomer concentration of 75%. We also measured the non-linear optical parameters-steepness parameter, refractive index, extinction coefficient, and dissipation factor to understand the suitability of the composite thin films for advanced optoelectronic devices.