Effect of SiO2 interfacial layer on InGaZnO-based memristors for neuromorphic computing applications

초록

To achieve progressive resistance modulation with memristors, we utilized InGaZnO (IGZO) films with a Pd top electrode to form a Schottky barrier at the interface. As oxygen vacancies (VO) were ionized and recombined in the IGZO layer depending on the applied voltage polarity, the magnitude of the barrier was smoothly adjusted, enabling analogous modulation of current. Because a native SiO2 layer was invariably formed on the Si bottom electrode (BE) during fabrication, we analyzed the impact of the SiO2 layer on the memristive characteristics of the IGZO layer through a comparison between memristors with differently formed SiO2 layers. Even when the native oxide was removed via wet etching, the subsequent IGZO sputtering induced oxidation at the Si BE interface by scavenging oxygen ions, resulting in a non-stoichiometric IGZO layer. Contrarily, when the interfacial SiO2 was intentionally deposited using an e-beam evaporator after wet etching, physical analysis showed that the scavenging of oxygen ions from the IGZO layer was inhibited. Among the fabricated samples, the memristor with the VO-rich non-stoichiometric IGZO layer exhibited improved state stability over time. These optimized IGZO memristors also displayed analogously tunable weight-update behavior when incorporated into neuromorphic synaptic devices, enabling artificial neural networks to achieve high pattern-recognition accuracy.

키워드