Correlation between thickness, grain size and optical band gap of CdI2 film

Abstract EN

Structural and optical property was studied as a function of film thickness for thermally evaporated CdI2 films.

Stoichiometric films (up to 250 nm thickness) showing hexagonal structure, and good c-axis alignment normal to glass substrate plane.

The optical absorption data indicate an allowed direct inter – band transition near the absorption edge with optical energy gap varies continuously from 2.9 eV to 3.6 eV.Part of the optical data was fitted to an indirect type transition to determine the indirect optical energy gap which also varies continuously from 2.2 eV to 3.1 eV .

Both energy gaps show thickness dependences, which can be explained qualitatively by a thickness dependence of the grain size through the decreasing of the grain boundary barrier height with grain size.