Revue des systemes de commutation representatifs et discussion detaillee d'une classe particuliere de ces systemes non identifiee correctement dans le passe. On presente les avantages de diodes planes MIM par rapport aux configurations fermees (sandwich) car la totalite de leur structure est ouverte et accessible directement a l'atmosphere gazeuse environnante ou au vide, qui affecte fortement le comportement

Bistable switching in electroformed metal–insulator–metal devices†

Polarized memory switching in mis thin films

Coexistence of negative differential resistance (NDR) and resistive switching (RS) memory is observed using a Ag vertical bar TiOx vertical bar F-doped-SnO2 memory cell at room temperature. Unlike other reports, the coexistence of NDR and RS strongly depends on the relative humidity levels at room temperature. The NDR disappears when the cells are placed in a dry air ambient (H2O < 5 ppm) or in vacuum, but the coexistence emerges and gradually becomes obvious after the cells are exposed to ambient air with relative humidity of 35%, and then becomes dramatically enhanced as the relative humidity becomes higher. Due to the excellent stability and reversibility of the coexistence of NDR and RS, a multilevel RS memory is developed at room temperature. Hydroxide ion (OH-) is induced by gas-phase water-molecule splitting on the surface and interface of the memory cell. The OH- interacts with oxygen vacancies and transports in the bulk of memory cell to facilitate the migration of Ag ions and oxygen vacancies along grain boundaries. These processes are responsible for the moisture-modulated and room-temperature coexistence. This work demonstrates moisture-modulated coexistence of NDR and RS for the first time and gives an insight into the influence of water molecules on transition-metal-oxide-based RS memory systems.

Coexistence of Negative Differential Resistance and Resistive Switching Memory at Room Temperature in TiOx Modulated by Moisture

Al and Ag2−xSe1+x layers are prepared by thermal evaporation. Al2O3 thin films are obtained after Al deposition by breaking the vacuum or by anodic oxydation of aluminium for the thicker one's. For an Al2O3 thickness of about 20 A, the I-U characteristics show a S-type differential negative resistance: after a formation process the commutation voltage stabilizes to a value VS. The memorized on-state vanishes quickly by application of a reverse voltage (Al being taken as the anode) or progressively by cancelling the applied voltage. The temperature dependence of the resistivity in the conducting state is metallic-like. In the off-state, conduction can be described by a tunneling mechanism through the Al2O3 layer. For thicker Al2O3 films (100 to 300 A) the (I-U) characteristics show a N-type differential negative resistance (DNR). After a forming process obtained by application of a voltage greater than a minimum VF, the samples develope a RDN effect similar to that found in MIM structures. All these properties are not sensitive to the atmosphere. These results are described in terms of metal ionic diffusion and filament formation. The shape of the (I-U) characterisitics is bound to the dimensions and the number of filaments.



Les couches d'aluminium et de Ag2−xSe1+x ont ete preparees par evaporation thermique, celles d'alumine ont ete obtenues en “cassant” le vide avant la deposition du semiconducteur et, pour les couches epaisses, par oxydation anodique de l'aluminium. Pour une epaisseur de 20 A d'alumine, les structures presentent une resistance differentielle negative (RDN) en forme de S. L'etat conducteur memorise disparait rapidement par application d'une tension inverse ou lentement en annulant la tension aux bornes de l'echantillon. L'evolution de la resistivite de l'etat conducteur avec la temperature est de type metallique. La conduction dans l'etat isolant peut etre decrite par un mecanisme tunnel a travers la couche d'alumine. Pour des epaisseurs de 100 a 300 A d'alumine, les structures presentent une resistance differentielle negative en forme de N semblable a celles rencontrees dans les structures MIM. Tous ces resultats sont interpretes a l'aide d'une diffusion d'ions argent et formation de filaments. La forme de la RDN est determinee par la taille et le nombre de filaments eux-memes lies a l'epaisseur d'isolant

Tadashi Shimizu

Papers

Humidity-sensitive electrical properties and switching characteristics of BN films