Bipolar Resistive Switching Characteristics of Thermally Evaporated V₂O₅ Thin Films

Abstract

Forming-free bipolar resistive switching has been reported in ITO/V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> /ITO structures. The sandwiched V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> film was synthesized by the sol-gel process, and it suffers from the issues of non-uniformity, low thermal stability, and short lifetime due to the presence of intercalated water molecules. In this work, thermal evaporation was employed for the deposition of amorphous V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> in ITO/V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> /ITO structures. Bipolar resistive switching characteristics were preserved and insensitive to annealing temperature below 300 °C. Switching disappears when the annealing temperature exceeds 350 °C due to the re-crystallization of the amorphous film. Ab initio molecular dynamics method was utilized to simulate the melt-quench process and generate the amorphous V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> structure. Significantly, lowered formation energies were found at some oxygen vacancy sites in amorphous structure. The simulation was in agreement with the proposed switching mechanism that the generation of mobile oxygen ions in V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> film was essential for the occurrence of resistive switching. The lifetime and the compatibility with IC fabrication of the devices have also been greatly improved.