Thickness dependence of refractive index and optical gap of PMMA layers prepared under electrical field

Optical parameters (refractive index, dispersion energy, optical gap) of polymethylmethacrylate (PMMA) layers prepared by spin coating and modified by electric field have been studied. Refractive index was measured using a refractometer, internal structure was investigated as a structural parameter (E _d) within the One Oscillator Model. Optical gap width (E _g ^opt) was assessed using Tauc Approximation from UV-Vis spectra. Surface morphology and roughness was investigated using an AFM. The electric field imposed during preparation of layers increases their refractive index. The highest increase in n (Δn = 0.042) was found for the thinnest PMMA layer (70 nm). Oriented layers have produced higher E _g ^opt than non-oriented ones for all studied values of thickness. The electrical field applied at preparation of the oriented layer will not change its surface morphology and roughness.