Depth-profiled characterization of complex refractive index of ion implanted optically transparent polymers using multilayer calculations and reflectance data

The material in the ion-modified surface layer formed in polymethylmethacrylate (PMMA) is optically characterized by calculations based on multilayer model and optical reflectance data. PMMA was subjected to a low energy (50 keV) silicon ion implantation at the fluences of 3.2 × 1015 cm−2 and 3.2 × 1016 cm−2. Both real and imaginary components of the complex refractive index of this optically transparent polymer are modeled in a geometry that includes a gradient of their in-depth spatial distribution.

► The complex refractive index of Si ion implanted PMMA is characterized in depth. ► Multilayer calculations and reflectance data are used to obtain index depth profile. ► The index change is close to the ion-modified surface, in a depth of about 100 nm. ► In depth, the refractive index of the ion-modified layer is gradually decreasing.