Exploration of optical behavior of Cd1−xNixTe thin films by spectroscopic ellipsometry

Abstract

We report on the tunability over the optical behavior of e-beam evaporated nanocrystalline thin films of Cd1−xNixTe (0 ≤ x ≤ 0.15). X-ray diffraction analysis reveals the polycrystalline nature of the film having zinc blend structure with a preferred growth direction along (111) plane parallel to the substrate. X-ray diffraction results also indicate that the grain size of the films decreases from 27.13 nm to 16.23 nm with an increase in Ni concentration from 0 to 15 at%. The compositional analysis of the film was carried out by energy dispersive x-ray analysis (EDX) which confirms the successful inclusion of Ni in CdTe matrix. Spectroscopic ellipsometery (SE) results demonstrate that the band gap of the grown films increases from 1.48 eV to 1.86 eV while refractive index (n) and extinction coefficient (k) decrease with the increasing Ni concentration. The increase in band gap energy of Cd1−xNixTe films as a function of Ni concentration was confirmed by spectrophotometric analysis.