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 (VSet) and reset voltage (VReset) 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.