Resistive Random Access Memory Device …
325
Fig. 4 Side view schematics of unipolar SET switching in RRAM device with a neutral oxygen
vacancies and b positively charged oxygen vacancies. Reprinted by permission from Springer
Nature, Applied Physics A: Materials Science & Processing [73], Copyright (2012)
(Fig. 4b) and this is observed in TiO 2 OxRRAM by Kwon et al. [59] using in situ
TEM. The electroforming process creates a radial temperature gradient due to Joule
heating within the CF. The Soret force then attracts the vacancies towards the CF and
since the vacancies are positively charged, they are attracted towards the negative
electrode.
By considering both thermophoresis and the Fick diffusion of oxygen ions under
the influence of Joule heating, the ion dynamics in OxRRAM can be described by
the following Soret-Fick continuity Eq. (1) [73, 74]:
∂η v
∂t
= ∇ J Fick + ∇ J Soret
(1)
where η v is the vacancy density, J Fick and J Soret are the fluxes induced by Fick
diffusion and thermophoresis, respectively.
Unlike unipolar OxRRAM systems, it is the electric field effects that dominate
in bipolar OxRRAM systems. One of more widely researched bipolar OxRRAM
325
Fig. 4 Side view schematics of unipolar SET switching in RRAM device with a neutral oxygen
vacancies and b positively charged oxygen vacancies. Reprinted by permission from Springer
Nature, Applied Physics A: Materials Science & Processing [73], Copyright (2012)
(Fig. 4b) and this is observed in TiO 2 OxRRAM by Kwon et al. [59] using in situ
TEM. The electroforming process creates a radial temperature gradient due to Joule
heating within the CF. The Soret force then attracts the vacancies towards the CF and
since the vacancies are positively charged, they are attracted towards the negative
electrode.
By considering both thermophoresis and the Fick diffusion of oxygen ions under
the influence of Joule heating, the ion dynamics in OxRRAM can be described by
the following Soret-Fick continuity Eq. (1) [73, 74]:
∂η v
∂t
= ∇ J Fick + ∇ J Soret
(1)
where η v is the vacancy density, J Fick and J Soret are the fluxes induced by Fick
diffusion and thermophoresis, respectively.
Unlike unipolar OxRRAM systems, it is the electric field effects that dominate
in bipolar OxRRAM systems. One of more widely researched bipolar OxRRAM