Structural and optical properties of Cu2Se/Yb/Cu2Se thin films

Abstract

In this study, two stacked layers of Cu2Se are nanosandwiched with 50 nm thick Yb slab. The films which are prepared by the thermal evaporation technique under vacuum pressure of 10–5 mbar are examined by the X-ray diffraction, scanning electron microscopy, energy dispersion spectroscopy and optical spectrophotometry techniques. The cubic phase of Cu2Se exhibits lattice contraction which results in strained structure and reduction in grain size upon insertion of Yb between two layers of Cu2Se. The nanosandwiching of Yb layer does not influence the optical energy band gap but significantly altered the optical conductivity parameters. The optical conductivity parameters are determined by the help of Drude-Lorentz approach for the dielectric dispersion. Particularly, while the scattering time at femtosecond levels and the drift mobility values increases, the free hole density decreases via the nanosandwiching procedure. The drift mobility and plasmon frequency of Cu2Se reached values of 35.2 cm2/Vs and 9.85 GHz, respectively, by the Yb nanosandwiching. The enhancements in mobility and free carrier density values make the Cu2Se thin films more appropriate for optoelectronic applications.