Sm-doping effect on optical and electrical properties of ZnO films

A series of ZnO: Sm films with Sm content of 0–1.0 at.% were deposited by a chemical solution deposition. The deposited films were characterized by X-ray diffraction, field emission scanning electron microscopy, UV–Vis and luminescent spectrophotometry, and electrical resistance measurement. The experiments revealed that the Sm doping first increased and then decreased the optical transmittance, band gap, and n-type conductivity with increasing Sm content. The film with the Sm content of 0.75 at.% showed optimal optical and electrical properties. The maximal band gap widening was about 0.19 eV. The resistance decrease of ~20 times was observed. The photoluminescence measurement indicated that the films showed a strong near band gap emission and a blue-green emission related to intrinsic defect. The refractive index, extinction coefficient, and dielectric constant of the films were calculated with the transmittance and reflectance spectra.