Controlling oxygen migration in YBa2Cu3O7-δ with short current pulses and device geometry

High current densities can induce the directional diffusion of atoms in metallic films. In
YBa2Cu3O7-δ (YBCO), this electromigration process selectively acts on oxygen, permitting to
vary the oxygen concentration in a targeted volume. This approach has proven successful in
mapping the phase diagram of the material as a function of carriers’ concentration [1] or as a
way to manufacture memristive devices owing to its reversibility under small bipolar
excitations [2]. Thus far, most of the investigations have been limited to pulsed excitation
with current/voltage pulses on a millisecond or longer scale, for which thermal effects
undeniably influence the process. In the present work, we explore the impact of pulse length
on the onset current of electromigration of YBCO bridges, covering the range from 100 ns to
1 ms. Then, using Y-shaped three-terminal devices, we demonstrate the possibility to
progressively displace oxygen vacancies on a hand-picked terminal without affecting the
neighboring ones. The oxygen-rich and oxygen-depleted propagating fronts are directly
visualized and are linked to the evolution of the electrical response. Finite element modelling captures these observations and predicts the spatiotemporal evolution of the vacancy fronts by accounting for transient Joule heating and oxygen diffusion due to electromigration. Together, these results establish insight into design rules for programmable, locally-selective oxygen control in YBCO, relevant for memristors and superconducting electronics.