Studying trivalent/bivalent metal ion doped TiO2 as p-TiO2 in bipolar heterojunction devices

Trivalent/bivalent metal ions doped TiO2 thin films (MxTi1−xO2, M = Cr3+, Fe3+, Ni2+, Co2+, Mn2+ and x = 0.01, 0.05, 0.1, 0.15, 0.2) were deposited on Indium–tin oxide (ITO) coated glass substrates by spin coating technique. X-ray photoelectron spectroscopy (XPS) showed Ti4+ oxidation state of the Ti2p band in the doped p-TiO2. The homogenous MxTi1−xO2 was used to support n-ZnO thin films with thickness ∼40–80 nm and vertically aligned n-ZnO nanorods (NR) with length ∼300 nm and 1.5 μm. Current (I)–voltage (V) characteristics for the Ag/n-ZnO/MxTi1−xO2/ITO/glass assembly showed rectifying behavior with small turn-on voltages (V0) < 1 V. The ideality factor (η) and the resistances in both forward and reverse bias were calculated. The temperature dependence performance of these bipolar devices was performed and variation of the parameters with temperature was studied.

► Trivalent/bivalent metal ion doped TiO2 through wet chemical synthesis method.
► Heterojunctional devices obtained with p-TiO2 thin film and aligned n-ZnO nanorods.
► The obtained devices show rectifying characteristics with small turn-on voltages.