Highly transparent plasma polymerized 2-Furaldehyde-n-Butyl methacrylate composite thin films with tunable linear and nonlinear optical properties and enhanced surface morphology for optoelectronic applications

Plasma polymerized (PP) homo and composite polymer thin films of 2-Furaldehyde (FD) and n-Butyl methacrylate (BM) are fabricated using a capacitively coupled glow discharge plasma. A homogeneous, smoother, and pinhole-free surface of the composite films is observed compared to that of the homopolymer. The composite films exhibit higher carbon content with a hydrocarbon skeleton (C−C, C−H), contributing to their improved stability. The films show enhanced optical transmittance (88 − 98%) in the visible region and exhibit tunable direct and indirect optical band gaps of (2.73 − 2.94 eV) and (2.26 − 2.38 eV), respectively. The oscillation energy is observed to be decreased, while the dispersion energy increased with the reduction of BM content, which may have occurred due to the improvement of electron transmission between the electronic bands. The refractive index ( η ) calculated using different empirical relationships shows almost similar values, while η decreases with increasing BM content, indicating enhanced photon-electron interactions in the thin films. This enhanced interaction results in a phase transition, causing a decreasing trend in both first-order linear susceptibility and third-order non-linear susceptibility. Furthermore, the composite films show more ordered structure than homopolymers, as evidenced by the values of Urbach energies. The non-linear refractive index improves with higher FD content, which enhances the polarizability because of the changes in the defect states within the films. By adjusting the monomer ratios, the optical properties of PP(FD-BM) films can be tuned, enabling their use in advanced optoelectronic and non-linear devices. PP(FD-BM) thin films exhibit smooth, pinhole free and flawless surface, along with tunable band gap and tailored linear and nonlinear optical properties.