Direct Visualization of Current-Stimulated Oxygen Migration in YBa₂Cu₃O_7−δ Thin Films

Abstract

The last years have witnessed major advancements in all-electrical doping control on cuprates. In the vast majority of cases, the tuning of charge carrier density has been achieved via electric eld eect by means of either a ferroelectric polarization or by using a dielectric or electrolyte gating. Unfortunately, these approaches are constrained to rather thin superconducting layers and require large electric elds in order 1 to ensure sizable carrier modulations. In this work, we focus on the investigation of oxygen doping in an extended region through current-stimulated oxygen migration in YBa 2 Cu 3 O 7−δ superconducting bridges. The underlying methodology is rather simple and avoiding sophisticated nanofabrication process steps and complex electronics. A patterned multiterminal transport bridge conguration allows us to electrically assess the directional counterow of oxygen atoms and vacancies. Importantly, the emerging propagating front of current-dependent doping δ is probed in situ by optical microscopy and scanning electron microscopy. The resulting imaging techniques, together with photo-induced conductivity and Raman scattering investigations reveal an inhomogeneous oxygen vacancy distribution with a controllable propagation speed permitting us to estimate the oxygen diusivity. These ndings provide direct evidence that the microscopic mechanism at play in electrical doping of cuprates involves diusion of oxygen atoms with the applied current. The resulting ne control of the oxygen content would permit a systematic study of complex phase diagrams and the design of electrically addressable devices.

Transverse barrier formation by electrical triggering of a metal-to-insulator transition

“…Our resistor network simulations show that the insulating barrier that forms during the M → I volatile switching concentrates not only the dissipated power but also the applied voltage. It is possible that the transverse barrier formation can occur in systems which feature a nonvolatile low-to-high-resistance switching caused by ion electromigration, such as rare-earth nickelates 77,78 , manganites [77][78][79][80][81][82] , and cuprates 77,79,83 . In fact, spatial patterns previously reported for the nonvolatile switching in YBa 2 Cu 3 O 7 83 , LSMO 84 and in NdNiO 3 85 can be rationalized by considering the tendency of low-to high-resistance switching to occur by the formation of a transverse insulating barrier.…”

Determination of the Oxygen Chain Ordering in REBa2Cu3O7–δ by Electrical Conductivity Relaxation Measurements

“…Understanding the mechanism behind these changes in the oxygen content and ordering is a key point in controlling the final superconducting properties of the CCs. Besides, it will also allow a better comprehension of other phenomena related with the oxygen content in REBCO films as, for example, the resistive switching. , …”

“…Besides, it will also allow a better comprehension of other phenomena related with the oxygen content in REBCO films as, for example, the resistive switching. 9,10 Within the family of REBCO, YBa 2 Cu 3 O 7−δ (YBCO) is probably the best-known and -studied compound since it was the first superconductor showing a T c above liquid-nitrogen temperature (LN 2 , 77 K). However, there are other REBCO compounds that could exhibit better electrical properties than YBCO aside from small improvements in T c and, therefore, be very attractive materials to be studied in depth.…”

Electrically‐Driven Oxygen Vacancy Aggregation and Displacement in YBa2Cu3O7−δ Films

“…In ref. [13] it has been shown that after electromigration part of the bridge becomes deoxygenated down to a certain minimum value x min whereas other zones are oxygenated up to an upper value x max . This can be understood as a consequence of a concentration‐dependent activation energy E a ( x ).…”

“…Recently, a radically different approach consisting in current‐induced migration of oxygen, has been proposed. [ 13 ] This technique has been implemented to scan the entire temperature‐hole concentration phase diagram in a single sample. [ 14 ] In this case, the agglomeration of oxygen vacancies manifests itself as a zone of higher reflectivity thus permitting to track the temporal evolution of the affected area by optical microscopy.…”