Understanding the Dual Nature of the Filament Dissolution in Conductive Bridging Devices.

The formation and rupture of conductive filaments (CFs) inside an insulating medium is used as hardware encoding of the state of a memory cell ("1" - "0") in filamentary-based conductive bridging memories. Currently accepted models explain the filament erase (reset) as the subtraction of conductive metal atoms from the CF; however, they do not fully account for the rich set of phenomena experimentally observed during the reset. The details of the filament erase are unraveled on the nanometer scale by means of an atomic force microscopy-based tomography technique enabling the 3D observation of erased CFs. "Non-broken" and "broken" CFs are observed, whereby the increase in resistance originates, respectively, from a constriction point in the current path and from an interrupted CF. We demonstrate that their existence and morphology can be related to the specific formation history of the CF, and we identify the physical volume of the CF as being mainly responsible for the type of filament erase.