Enhancement of Resistive Switching Characteristics of Sol–Gel TiO x RRAM Using Ag Conductive Bridges

Abstract

In this article, the effects of active Ag electrodes on the ROFF/RON ratio, SET/RESET voltages, and endurance characteristics of a sol-gel TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> resistive memory are investigated. Stable bipolar resistive switching (RS) behavior with a large R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</sub> /R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> ratio of 105 is observed in an Ag/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> /n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -Si resistive memory. The SET and RESET processes can only be triggered by positive and negative voltages, respectively. Nonpolar RS behavior is found when directly using a tungsten probe to measure the I-V curves of a TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> /n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -Si device. A high voltage of ~+40 V is needed to induce the SET process. In addition, the RS behavior is not stable and can only repeat few times. When the top and bottom electrodes are both Ag (Ag/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> /Ag), the SET process can be easily triggered by a low voltage regardless of the voltage polarity. However, the RESET process does not happen in the following voltage cycles. Dramatic differences in the RS characteristics of these devices verify the impact of the Ag electrode on the RS characteristics of the sol-gel TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> layer.