A Combined Ab Initio and Experimental Study on the Nature of Conductive Filaments in <tex-math notation="TeX">Pt/ Hf O₂/ Pt </tex-math> Resistive Random Access Memory

Through ab initio calculations, we propose that the conductive filaments in Pt/HfO2/Pt resistive random access memories are due to HfOxsuboxides, 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-nm2filaments embedded in an insulating HfO2matrix. 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.