  In this work, we investigate the behavior of Al2O3/TiO2-x cross-point
memristors in cryogenic environment. We report successful resistive switching
of memristor devices from 300 K down to 1.5 K. The I-V curves exhibit negative
differential resistance effects between 130 and 1.5 K, attributed to a
metal-insulator transition (MIT) of the Ti4O7 conductive filament. The
resulting highly nonlinear behavior is associated to a maximum ION/IOFF ratio
of 84 at 1.5 K, paving the way to selector-free cryogenic passive crossbars.
Finally, temperature-dependant thermal activation energies related to the
conductance at low bias (20 mV) are extracted for memristors in low resistance
state, suggesting hopping-type conduction mechanisms.
