Theoretical Study of Ag Interactions in Amorphous Silica RRAM Devices

In this study, Density Functional Theory (DFT) calculations were used to model the incorporation and diffusion of Ag in Ag/a-Si02/Pt resistive random-access memory (RRAM) devices. The Ag clustering mechanism is vital for understanding device operation and at this stage is unknown. In this paper an O vacancy (Vo) mediated cluster model is presented, where the Vo is identified as the principle site for Ag
⁺
reduction. The Ag
⁺
interstitial is energetically favored at the Fermi energies of Ag and Pt, indicating that Ag
⁺
ions are not reduced at the Pt electrode via electron tunneling. Instead, Ag
⁺
ions bind to Vo forming the [Ag/Vo]
⁺
complex, reducing Ag
⁺
via charge transfer from the Si atoms in the vacancy. The [Ag/Vo]
⁺
complex is then able to trap an electron forming [Ag/Vo]
⁰
at the Fermi energy of Pt. This complex is then able to act as a nucleation site for of Ag clustering with the formation of [Ag2/Vo]
⁺
which is reduced by the above mechanism.