Search

We show that resistive switching in the SiO2/Cu stack can be modified by a brief exposure of the oxide to an Ar plasma. The set voltage of the SiO2/Cu stack is reduced by 33%, while the breakdown voltage of the SiO2/Si stack (control) is almost unchanged. Besides, the Ar plasma treatment suppresses the negative photoconductivity or optical resistance reset effect, where the electrically formed filamentary conductive path consisting of Cu-ion and oxygen-vacancy clusters is disrupted by the recombination of the oxygen vacancies with nearby light-excited oxygen ions. From the enhanced O-H peak in the Fourier-transform infrared spectrum of the plasma-treated oxide, it is proposed that the Ar plasma has created more oxygen vacancies in the surface region of the oxide. These vacancies in turn adsorb water molecules, which act as counter anions (OH-) promoting the migration of Cu cations into the oxide and forming a more complete Cu filament that is less responsive to light. The finding points to the prospect of a control over the optical resistance reset effect by a simple surface treatment step. [ABSTRACT FROM AUTHOR]

We show that the negative photoconductivity property of the nanoscale filamentary breakdown path in the SiO2 electrolyte of the SiO2/Cu conductive bridge resistive random access memory (CBRAM) stack is affected by the number of positive-voltage sweeps applied to the Cu electrode (with respect to a non-metal counter electrode). The path's photo-response to white light, of a given intensity, is suppressed with an increasing number of applied positive-voltage sweeps. When this occurs, the path may only be disrupted by the light of a higher intensity. It is further shown that the loss of the path's photosensitivity to the light of a given intensity can be recovered using a negative-voltage sweep (which eliminates the path), followed by the reformation of the path by a positive-voltage sweep. The above behavior is, however, not seen in the SiO2/Si stack (which involves a non-metal Si electrode), suggesting that the photo-response modulation effect is related to the Cu electrode. The demonstrated reversible electrical modulation of the path's photo-response may afford greater flexibility in the electro-optical control of the CBRAM device. [ABSTRACT FROM AUTHOR]

This study shows that a majority (70%) of TiN/HfOx/TiN devices exhibit failed complementary resistance switching (CRS) after forming. In conjunction with the consistent observation of a large non-polar reset loop in the first post-forming voltage-sweep measurement, it is proposed that breakdown of the TiN/HfOx interfacial oxide layers (crucial in enabling CRS) and the accompanied formation of Ti filaments (due to Ti migration from the TiN cathode into the breakdown path) resulted in CRS failure and the observed non-polar reset behavior. This hypothesis is supported by the significant reduction or complete elimination of the large non-polar reset and CRS failure in devices with a thin Al2O3 layer incorporated at the TiN-cathode/HfOx or both TiN/HfOx interfaces. The higher breakdown field of the thin Al2O3 enables it to sustain the forming voltage until the forming process is interrupted, thus enabling CRS via oxygen exchange with the adjacent vacancytype filament formed in the HfOx. [ABSTRACT FROM AUTHOR]

The role of the bottom interfacial layer (IL) in enabling stable complementary resistive switching (CRS) in the TiN/HfOx/IL/TiN resistive memory device is revealed. Stable CRS is obtained for the TiN/HfOx/IL/TiN device, where a bottom IL comprising Hf and Ti sub-oxides resulted from the oxidation of TiN during the initial stages of atomic-layer deposition of HfOx layer. In the TiN/HfOx/Pt device, where formation of the bottom IL is suppressed by the inert Pt metal, no CRS is observed. Oxygen-ion exchange between IL and the conductive path in HfOx layer is proposed to have caused the complementary bipolar switching behavior observed in the TiN/HfOx/IL/TiN device. [ABSTRACT FROM AUTHOR]