An oxygen vacancy mediated Ag reduction and nucleation mechanism in SiO2 RRAM devices

• Autores: K. Patel, J. Cottom, Michel Bosman, A.J. Kenyon, Alexander L. Shluger
• Localización: Microelectronics reliability, ISSN 0026-2714, Nº. 98, 2019, págs. 144-152
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • Density Functional Theory (DFT) calculations were used to model the incorporation and diffusion of Ag in Ag/SiO2/Me (Me = W or Pt) resistive random-access memory (RRAM) devices. We consider an O vacancy (VO) mediated model of the initial stages of Ag clustering, where the VO is identified as the principle site for Ag+ reduction. The Ag+ interstitial is calculated to be energetically favoured inside a-SiO2 at the Fermi energies of Ag, W and Pt. The adiabatic diffusion barriers of Ag+ are found to be lower than those for Ag0 with a strong dependence on the local network structure, supporting Ag+ being the mobile species during device operation. Ag+ ions bind to VO forming the [Ag/VO]+ complex. The [Ag/VO]+ complex is then reduced by trapping an electron forming [Ag/VO]0. By sampling every VO in a 216-atom cell of a-SiO2 we demonstrate that this mechanism can occur only at 33%, 33% and 11% of O vacancies at the Ag, W and Pt electrodes, respectively. This complex can subsequently act as a nucleation site for Ag clustering with the formation of [Ag2/VO]+, which is reduced by trapping an extra electron.