A Materials Approach to Resistive Switching Memory Oxides

Abstract

Several oxides have recently been reported to have resistance-switching characteristics for nonvolatile memory (NVM) applications. Both binary and ternary oxides demonstrated great potential as resistive-switching memory elements. However, the switching mechanisms have not yet been clearly understood, and the uniformity and reproducibility of devices have not been sufficient for gigabit-NVM applications. The primary requirements for oxides in memory applications are scalability, fast switching speed, good memory retention, a reasonable resistive window, and constant working voltage. In this paper, we discuss several materials that are resistive-switching elements and also focus on their switching mechanisms. We evaluated non-stoichiometric polycrystalline oxides (Nb₂OSUB5/SUB, and ZrOSUBx/SUB) and subsequently the resistive switching of CUSUBx/SUBO and heavily Cu-doped MoOSUBx/SUB film for their compatibility with modern transistor-process cycles. Single-crystalline Nb-doped SrTiO₃(NbSTO) was also investigated, and we found a Pt/single-crystal NbSTO Schottky junction had excellent memory characteristics. Epitaxial NbSTO film was grown on an Si substrate using conducting TiN as a buffer layer to introduce single-crystal NbSTO into the CMOS process and preserve its excellent electrical characteristics.