Resistance random access memory based on a thin film of CdS nanocrystals prepared via colloidal synthesis

We demonstrate that resistance random access memory (RRAM) can be fabricated based on CdS-nanocrystal thin films. A simple drop-drying of the CdS-nanocrystal solution leads to the formation of uniform thin films with controlled thickness. RRAMs with a Ag/Al₂O₃/CdS/Pt structure show bipolar switching behavior, with average values of the set voltage (V_Set) and reset voltage (V_Reset) of 0.15 V and -0.19 V, respectively. The RRAM characteristics are critically influenced by the thickness of the Al₂O₃ barrier layer, which prevents significant migration of Ag into the CdS layer as revealed by Auger electron spectroscopy (AES). Interestingly, RRAM without an Al₂O₃ layer (i.e., Ag/CdS/Pt structure) also shows bipolar switching behavior, but the polarity is opposite to that of RRAM with the Al₂O₃ layer (i.e., Ag/Al₂O₃/CdS/Pt structure). The operation of both kinds of devices can be explained by the conventional conductive bridging mechanism. Additionally, we fabricated RRAM devices on Kapton film for potential applications in flexible electronics, and the performance of this RRAM device was comparable to that of RRAMs fabricated on hard silicon substrates. Our results show a new possibility of using chalcogenide nanocrystals for RRAM applications. Uniform thin films of CdS nanocrystals are formed via simple drop-drying of colloidally synthesized nanocrystals. The resistance random access memory (RRAM) fabricated using these CdS nanocrystal thin films shows bipolar switching behavior with set and reset voltages of 0.15 V and -0.19 V, respectively. Our results show a new possibility of using chalcogenide nanocrystals for RRAM applications.