Theoretical Study of Ag Interactions in Amorphous Silica RRAM Devices

K Patel and J Cottom and M Bosman and AJ Kenyon and AL Shluger, 2018 25TH IEEE INTERNATIONAL SYMPOSIUM ON THE PHYSICAL AND FAILURE ANALYSIS OF INTEGRATED CIRCUITS (IPFA) (2018).

In this study, Density Functional Theory (DFT) calculations were used to model the incorporation and diffusion of Ag in Ag/a-SiO2/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 Ag-2/Vo(+) which is reduced by the above mechanism.

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