Resistive switching characteristics of the Nb:SrTiO₃/YBa₂Cu₃O_7−x structure

Resistive switching (RS) devices based on Nb:SrTiO 3 (NSTO) hold significant potential for next-generation data storage due to their tunable resistance, stability, and low power consumption. The majority of existing research studies have predominantly focused on metal/NSTO structures that utilize single-crystal NSTO. Although this configuration exhibits superior performance, it is costly and cannot be easily integrated. Another important point is that epitaxial structures can enhance device stability because of their excellent interfaces. However, epitaxial growth of metals on NSTO poses significant challenges due to inherently high structural mismatches, which has led to inconsistent results reported by various researchers employing the same metal/NSTO structure. In this study, NSTO films with different Nb doping amounts were prepared on YBa 2 Cu 3 O[Formula: see text][Formula: see text] (YBCO) layers to form NSTO/YBCO heterostructures. YBCO serves as both the electrode and the epitaxial heterolayer material for NSTO. The photogenerated voltage and RS properties of epitaxially grown NSTO/YBCO structures were investigated in detail. At a low Nb doping amount, NSTO cannot produce sufficient photogenerated carriers, while excessive Nb doping results in a low interface barrier height, causing the photogenerated open-circuit voltage of the NSTO/YBCO structure to initially increase and then decrease with the increase in Nb doping amount (the peak value is observed at a Nb doping concentration of 1%). On the other hand, the electrical conductivity of NSTO increases with Nb doping, leading to an increase in the photogenerated short-circuit current. Further, the RS characteristics of the NSTO/YBCO structure were investigated, and clockwise and counterclockwise RS behaviors under low and high bias voltages were observed, respectively. At low voltages, the clockwise RS effect is primarily attributed to the increased interfacial barrier resulting from the migration of oxygen vacancies in YBCO. Conversely, at high voltages, the migration of oxygen ions within NSTO leads to a reduction in the interfacial barrier, thereby inducing a counterclockwise RS effect. In addition, at low bias voltages, the resistance ratio between the high-resistance state and the low-resistance state under [Formula: see text] 1/[Formula: see text] 2 V bias voltages first increases and then decreases as the Nb doping amount increases, with the highest resistance ratio (>100) observed at 1% Nb doping. These findings provide novel insights into the RS mechanism, and it is envisaged that they will promote the application of conductive oxides in RS devices and the development of multilevel memory devices.