J. H. Q. Palhares, Y. Beilliard, F. Alibart, E. Bonturim, D. Z. de Florio, F. C. Fonseca, D. Drouin and A. S. Ferlauto. Oxygen vacancy engineering of TaOx based resistive memories by Zr doping for improved variability and synaptic behavior, Nanotechnology 32, 405202 (2021).