Doping effect of Sm on the energy gap and optical dispersion of a-Se

Abstract

The optical transmission T(λ) as well as the reflection R(λ) spectra has been recorded, in the spectral range of 500-2500 nm, for thermally deposited Sm doped a-Se films. The X- ray diffraction technique was used to critically identify the structural nature of the studied films. The current optical theories and models were applied to analyze the recorded spectra and to calculate various interesting optical parameters. These include: dispersion of the two components of both complex refractive index (ñ = n - ik) and complex dielectric constant (ε1 and ε2), energy gap (Eg), Urbach energy (Eu), single oscillator energy (Eo), lattice oscillating strength (E1), material dispersion M(λ) and the wavelength at zero material dispersion (λc). At this point, a similar non-monotonic trend is observed for the compositional dependence of various parameters. This has been ascribed to the disorder and/or structural defects introduced due to the incorporation of Sm, up to 0.008 % Sm, in the a-Se matrix. Besides, a trial has been made thus estimating the inter-band transitions for the Se-Sm samples investigated.