Investigation of phase formation of Bi₂Sr₂CaCu₂O₈₊ₓ under oxygen-free conditions and its application in resistance switching

Abstract

This paper investigates the growth process of Bi₂Sr₂CaCu₂O₈₊ₓ (Bi-2212) films using the pulsed laser deposition method in both oxygen and oxygen-free (nitrogen) conditions. Furthermore, the resistance switching (RS) effect of Bi-2212/Nb: SrTiO₃ (NSTO) structure is explored. Bi-2212 films are deposited in oxygen and nitrogen atmospheres respectively, and the effects of laser energy, deposition temperature, atmospheric pressure, and oxygen diffusion process on phase formation and superconductivity are thoroughly studied. The high-quality Bi-2212 phase can be obtained at a deposition temperature of 800 °C, laser energy of 250 mJ, and an oxygen or nitrogen pressure of 65 Pa. The low-temperature diffusion process further enhances the superconducting properties, with oxygen-diffused samples exhibiting critical transition temperatures of approximately 83 K (deposition in oxygen) and 74 K (deposition in nitrogen). Additionally, the RS effect of Bi-2212/NSTO structures is investigated, where Bi-2212 is used as both the electrode and the hetero-layer for NSTO. Oxygen vacancies inherently present in Bi-2212 migrate to the Bi-2212/NSTO interface under low voltage, increasing the interfacial barrier. However, as the bias voltage progressively increases, oxygen ions in NSTO migrate into Bi-2212, resulting in the formation of Vo on the NSTO side, thereby reducing the interfacial barrier height. As a result, the Bi-2212/NSTO structure exhibits two different RS characteristics under different voltages. These results provide experimental references for the application of Bi-2212 in oxidizable substrates, circuits, and RS effect devices.