Characterization of highly conducting PbO-doped Cd₂SnO₄ thick films

Abstract

The factors contributing to the high conductivity of doped thick films of Cd₂SnO₄ were identified and their influence on the character of the films is explained. The dopant induction is through the glass and is effected after the film deposition. The films with dopant concentrations of 0.066-3.3 wt.% were fired at 500-900 ° C. All the samples have orthorhombic crystal structure. The lattice parameters and unit cell volume varied with the preparation conditions. The Burstein effect was observed in these films for the first time. The optical absorption edge shifted towards the UV region, from 534 to 514 nm. The apparent band gap increased from 2.32 to 2.41 eV. The sheet resistance correspondingly decreased by five orders of magnitude (from 5×10⁶to 3×10 Ω/∝ ). The morphology of the film surface appeared to be a single network of clusters resulting in a decrease in the barrier resistance. The binding energy of the Pb 4f_7/2 core electrons decreased from 141.86 to 138.2 eV indicating Pb²⁺ → Pb⁴⁺+2e− . This dopant oxidation and structural defects such as oxygen vacancies and cadmium interstitials contributed to the conductivity as did the apparent increase in carrier mobility.