With Flash memory rapidly approaching the physical limits of scalability, research on new memory concepts has significantly accelerated. Resistive Random Access Memory (RRAM) is a promising candidate for future memory applications due to its high density, excellent scalability, and simple structure. RRAM is also characterized by low operating voltage (less than 2V), fast switching speed (below 10 ns), and a long retention time. In the literature, a broad spectrum of electronic and/or ionic switching mechanisms for oxide-based memory has been suggested: a model based on trapping of charge carries, electrochemical migration of oxygen vacancies, electrochemical migration of oxygen ions, a unified physical model, a filament anodization model, a thermal dissolution model, and others. However, a proper fundamental understanding of the switching mechanism is still missing and is thus a high priority task.
We associate the resistive switching behavior in oxide-based memory with the formation and rupture of a Conductive Filament (CF). The CF is formed by localized oxygen vacancies or domains of oxygen vacancies. Formation and rupture of a CF is due to a redox reaction in the oxide layer under a voltage bias. The conduction is due to electron hopping between these oxygen vacancies. For modeling of the Set and Reset process in oxide-based memory by Monte Carlo techniques, we describe dynamics of oxygen ions and electrons in an oxide layer as follows: 1) an electron hops into an oxygen vacancy from an electrode; 2) an electron hops from an oxygen vacancy to an electrode; 3) an electron hops between two oxygen vacancies; 4) formation of an oxygen vacancy by an oxygen ion moving to an interstitial position; 5) annihilation of the oxygen vacancy by moving the oxygen ion to the oxygen vacancy; 6) movement of the oxygen ion between the interstitials.