First principles investigation of oxygen vacancies filaments in polymorphic Titania and their role in memristor's applications

Abstract

• Basic memristor characteristics are investigated for oxygen vacancies filaments in polymorphic Titania. • The electronic modification subsequently with the creation of the oxygen vacancies in TiO 2 phases have been investigated using density functional theory in depth which could support underlying mechanism of resistive switching . • Integrated charge density plots depicted charge transfer mechanism of three crystalline phases of TiO 2 . • The conductivity of the phases increased with increasing the number of oxygen vacancies; and eventually resulted that the considered phase opted the low resistance state. • From iso-surface charge density, integrated charge density and formation energy calculations, it is predicted that brookite phase of TiO 2 having 3V o is more stable and more conductive for various applications. Inconsistency of resistive switching parameters in memristors is a major challenge in the development of memory devices. These variability issues can be resolved by using materials having capability of easily growing conducting filaments and less value of oxygen vacancy formation energy (OVFE). In this first principle study, device to device variability by the electronic modification subsequently with the creation of the oxygen vacancies in TiO 2 phases have been investigated using density functional theory. The lattice constants, OVFE, density of states (DOS), partial density of states (PDOS), iso-surface charge density and integrated charge density are calculated to understand the structural and electronic properties of polytype TiO 2 with single-, di- and tri-oxygen vacancy (V o ) at atomistic level. It is found that by introducing the V o s, defect states are formed within the band gap, which caused to increase the conductivity of crystalline phases of TiO 2 . The conductivity of the phases increased with increasing number of V o s resulting in low resistance state of the opted phase. Existence of various stages of CFs and formation energy at various concentration of V o s predicts the implementation of constructive role of noise to enhance the efficiency and stability of the Titania based memristors. On the basis of easily growing conducing filaments having higher concentration of V o s with lesser OVFE, it is predicted that brookite phase of TiO 2 having 3V o s is more suitable in overcoming inconsistency issues related to resistive switching in low power consuming memristors devices.