HfO2/Ti Interface Mediated Conductive Filament Formation in RRAM: An Ab Initio Study

International audienceWe address the role of the Ti/HfO2 interface on the conductive filament (CF) formation within the context of oxide-based resistive random access memories (OxRRAMs). We investigate oxygen defects formation and diffusion at the interface through ab initio calculations. The calculated diffusion energy barriers compare well with the available experimental data. Through the interface region charge analysis and the associated energies with O defect formation and migration into Ti, our results support a probable CF growth from the interface region toward the electron injecting electrode, which acts as a cathode. Hence, for a Ti/HfO2-based OxRRAM supported by the calculation results, we present a pertinent CF growth model by considering its earliest stages, which is relevant for device modeling

A Combined Ab Initio and Experimental Study on the Nature of Conductive Filaments in Pt/HfO2/Pt Resistive Random Access Memory

International audienceThrough ab initio calculations, we propose that the conductive filaments in Pt/HfO 2 /Pt resistive random access memories are due to HfO x suboxides, possibly tetragonal, where x ≤ 1.5. The electroforming process is initiated by a continuous supply of oxygen Frenkel defect pairs through an electrochemical process. The accumulation of oxygen vacancies leads to metallic suboxide phases, which remain conductive even as ultranarrow 1-nm 2 filaments embedded in an insulating HfO 2 matrix. Our experiments further show that the filaments remain as major leakage paths even in the OFF-state. Moreover, thermal heating may increase the OFF-state resistance, implying that there are oxygen interstitials left in the oxide layer, which may recombine with the oxygen vacancies in the filaments at high temperature