Ellipsometrical characterization of complex refractive index depth profile of 50 keV silicon ion implanted PMMA

Multiangle reflection ellipsometry is applied to characterize the refractive index change of the material in the subsurface layer produced by ion implantation of polymethylmethacrylate (PMMA) with low-energy (50 keV) silicon ions at fluences ranging from 1014 to 1017 cm−2. By employing an effective medium approximation, the in-depth distribution of both real and imaginary parts of the complex refractive index of ion-modified material near the surface was modeled. The degree of in-depth modification of the target PMMA material upon ion implantation was established. A distinct fluence level was found that produced a maximum efficiency of the ion-induced change of the optical properties of the material. The ellipsometrical depth profiling of the refractive index of silicon ion implanted PMMA was proved with data obtained by reflectance spectroscopy and X-ray photoelectron spectroscopy. ► Refractive index depth profile is modeled in PMMA implanted with 50 keV silicon ions. ► The complex refractive index is characterized by multiangle reflection ellipsometry. ► The index depth profiles are modeled for different ion fluences. ► A fluence level is established for the most efficient refractive index change.