Tuning the electrical and optical properties of topological insulator Bi2Se3 by Ar+ ion irradiation

We employed X-ray diffraction analysis, electron transport measurements, and optical ellipsometry to investigate the topological insulator Bi2Se3 before and after argon ion irradiation with an energy of 15 keV and a fluence of 5.1015 cm-2. The electrical resistivity in the temperature range of 2-300 K and optical properties in the spectral range of 1250-40000 cm-1 at room temperature were measured. After irradiation, the rocking curve exhibited five local maxima, suggesting the crystal had fragmented into five mosaic blocks. The temperature-dependent electrical resistivity was modeled using a phenomenological approach accounting for electron-phonon and electron-electron scattering mechanisms. Irradiation led to enhancements in both scattering processes and an increase in electrical resistivity. Notable alterations were observed in the optical properties after irradiation: a more than twofold decrease in maximum optical conductivity, emergence of additional features in the infrared region of the imaginary part of dielectric permittivity, and reduction in reflectivity magnitude across the entire spectral range. We assume that such changes are associated with a change in the electronic structure of the irradiated layer.