Cu doping effect on the resistive switching behaviors of CoFe₂O₄ thin films

Spin-coated Cu_xCo_1−xFe₂O₄ (x = 0, 0.2, 0.4, 0.6, and 0.8) thin films were prepared on Pt/TiO₂/SiO₂/Si substrates. Pt/Cu_xCo_1−xFe₂O₄/Pt structures were fabricated to investigate the effect of Cu doping concentration on the resistive switching behaviors. Structural and morphology characterizations revealed that Cu doping improved the crystallization of the thin films as compared to undoped CoFe₂O₄. Current–voltage characterization showed that all Cu_xCo_1−xFe₂O₄ thin films showed unipolar resistance switching, but the distribution range of the set voltage, reset voltage, and resistances were much reduced by Cu doping. Clear improvement in the stability of these parameters started to appear with x = 0.4, and the optimized performance was observed in the Pt/Cu_0.6Co_0.4Fe₂O₄/Pt structure. The improved stability of the switching parameters was attributed to the enhancement of hopping process between the Fe ions and the Cu ions in the spinel lattice. Our results indicated that appropriate adjustment of the doping elements in oxides can be a feasible approach in achieving stable resistance switching memory devices.