Preparation and properties of Sol–Gel derived CuFeO<sub>2</sub> thin films by dip-coating technique

CuFeO2 crystal thin films were successfully prepared by dip-coating technique through sol–gel route on silica glass substrates. Heat treatment under nitrogen atmosphere was necessary to obtain monovalent Cu and 800–900°C firing was indispensable to prepare CuFeO2 stable phase, and 2–9 h heat-treatment was appropriate to lower the electrical resistivity. For the dip-coated films, CuO impurity phase was observed in Cu:Fe = 1:1 solution from X-ray diffraction pattern (XRD), and thus the Cu containing solution of Cu:Fe = 0.99:1, 0.97:1, 0.95:1, 0.9:1and 0.8:1 were prepared to eliminate excess CuO phase. Too lower content of Cu such as 0.9:1 and 0.8:1 provided Fe oxides as impurity phase, but slight decrease of Cu iecreased the electric resistivity although CuO was still slightly observed by XRD. The visible transparency of the films was nearly 10%, and some films of conduction type was confirmed as p-type by measuring Hall effect.