Synergistic Resistive Switching Mechanism of Oxygen Vacancies and Metal Interstitials in Ta2O5

Ta2O5 is extensively studied as a data-storage material for resistance random access memory (RRAM). The resistive switching (RS) in Ta2O5-based RRAM is generally believed to be due to the diffusion of oxygen vacancy (Vo) inside the oxide, while the role of metal interstitials is paid less attention. Here, on the basis of first-principles calculations, we show that the role of interstitial Ta (Ta-i) is competitive under the oxygen-poor condition and should also contribute to RS in Ta2O5. This is obvious by our calculated comparable energy barriers for the diffusion of Vo and Ta-i, which are 3.5 and 3.7 eV, respectively. Furthermore, the presence of electric field in working devices will enhance the migration of Ta-i due to its higher charge states compared to Vo. Meanwhile, Ta-i will introduce more defect states closer to the conduction bands and, thus, is more effective on tuning the electronic structure of Ta2O5. The present work unravels the contribution of Ta cations in RS of tantalum oxide based RRAM, presenting a synergistic RS mechanism of oxygen vacancies and metal interstitials, which should be helpful for optimizing and designing novel RRAM devices.