Exploration of thin film CoFe2O4 memristors with asymmetric electrodes

Abstract

Memristors have recently attracted significant research interest for applications in memory, neuromorphic computing, and cryptography, with complementary metal-oxide-semiconductor compatible fabrication essential for their integration into modern technology. In this paper, a memristor based on a CoFe₂O₄ thin film is developed and studied by varying its metal top electrode (Ag, Au, or Cr) and its silicon bottom electrode (p- or n-type). In the memristor, oxygen vacancies come together to form conducting filaments spanning from one electrode to another, which are used to change the device’s resistance. Through tweaking the electrode materials, different charge particles such as Ag⁺ ions in the case of silver, positively charged holes in the case of p-type silicon, or negatively charged electrons in the case of n-type silicon, can be used to change the memristor’s behavior and durability. Here, the memristors were able to achieve a resistance ratio of ∼100, a switching voltage of ∼4 V, and excellent retention with only a 6.1 % change in resistance after +5 V set and 0.56 % for a -5 V set after 1 h. The influx of reduced metal ions in memristors utilizing Ag top electrodes makes them more electrically durable than the memristors using Au or Cr. An augmented linear ion model is developed to demonstrate the undesirable effects that scaling will have on the resistance ratio of miniaturized memristors. Without taking these material and scaling effects into account, the introduction of memristors in current technologies will be difficult and challenging.