Surface morphology and optical properties of thin films of plasma polymerized methyl acrylate

Abstract

Thermally stable plasma polymerized methyl acrylate (PPMA) thin films are fabricated onto spotless glass substrates by AC power plasma polymerization technique. Field emission scanning electron micrographs of these films exhibit clusters/agglomerations on the surface. Energy dispersive x-ray analysis confirms the existence of 52.38, 52.63 and 51.55% of carbon and 47.62, 47.31 and 46.45% of oxygen, respectively in 170, 230 and 290 nm thick PPMA films. The molecular vibrations of various natures observed by attenuated total reflectance Fourier transform infrared spectroscopy of methyl acrylate and PPMA represent that the percentage of hydrophilic groups is smaller than the hydrophobic groups. Thermogravimetric analyses demonstrate that the major weight loss occurs in the temperature range from 500 to 850 K. Ultraviolet–visible spectroscopy demonstrates that the allowed direct energy band gap varies from 3.77 to 3.83 eV, whereas the indirect energy band gap alters from 3.40 to 3.48 eV with film thicknesses from 120 to 290 nm. Other optical parameters such as Urbach energy, refractive index, optical extinction coefficient, dielectric constants, quality factor, and skin depth have also been investigated for the PPMA thin films to elucidate their suitability in optoelectronic devices.