ZnIn2Se4 has a polycrystalline structure in as synthesized
condition. It transforms to nanostructure grains of ZnIn2Se4 upon
thermal deposition as thin films. The optical properties of as deposited
ZnIn2Se4 films are studied using spectrophotometer measurements of
transmittance and reflectance at normal incidence of light in wavelength
range (450–2500) nm. The refractive index and absorption index are
calculated and it is found that they are independent of film thickness in
the thickness range (500–790) nm. Absorption analysis showed two types of
electronic transitions; indirect allowed transition with energy gap 1.76 eV
accompanied by phonon of energy 25 meV and direct allowed transition with
energy gap 2.3 eV. The dispersion analysis showed that the oscillator
energy, dispersion energy, dielectric constant at infinite frequency and
lattice dielectric constant are 2.49 eV, 14.36 eV, 6.84 and 8.17,
respectively.