High ON/OFF Ratio and Quantized Conductance in Resistive Switching of ${\rm TiO}_{2}$ on Silicon

TiO₂ has been investigated extensively as an active resistive switching (RS) material for resistive random access memory. In this letter, single-crystal anatase- TiO₂ thin films fabricated on silicon by atomic layer deposition are used to realize highly stable and clean bipolar RS behavior with a record high ON/OFF ratio (~10⁷) and low leakage current in the high-resistance state. The switching characteristics resemble those of electrochemical memories via formation and dissolution of conductive filaments (CFs) composed of oxygen vacancies, and small numbers of quantized channels are reproducibly observed in the low-resistance state, consistent with quantized conductance (QC) found in conventional electrolytic systems and indicating its potential for forming ultrathin CF amenable to device scaling. A detailed analysis of QC and contact resistance is presented. The emergence of QC is believed to be related to the single-crystal nature of the TiO₂ thin films.