Thickness-dependent optical band gap in one-dimensional Ca3Co2O6 nanometric films

► The optical properties of Ca3Co2O6 thin films were found dependent on the film thickness. ► The band gap varies from 1.3 to 1.5 eV when the thickness increases from 35 to 100 nm. ► The gap evolution is described in terms of grain size and amorphous effect. ► This is similar to the variation of the magnetic properties with the film thickness. ► Magnetic and optical properties have similar origins related to the particular structure.