Transparent resistive random access memory for transparent electronics

Abstract

In this thesis, the novel memory device, fully transparent memory, was first studied for the transparent electronics. This device is based on the conventional resistive random access memory (RRAM) device, which exhibits nonvolatile resistive switching characteristics. When a transition metal oxide (TMO), which is one of the resistive switching materials used in RRAM, and transparent materials such as substrate and electrode in transparent electronics are combined, completely transparent and nonvolatile resistive switching memory device could be successfully achieved. This thesis is focused on the fabrication and evaluation of this device. To embody the real transparent device, we fabricated a transparent resistive random access memory (TRRAM) device based on an ITO/ZnO/ITO capacitor structure. As a result, the TRRAM device exhibited excellent transparency (~ 81 %) in visible region, low switching voltage (< 3 V), and good reliability (> $10^5$ retention time, > $10^2$ cycles). Additionally, we found that the conduction is dominated by Ohmic behavior in the LRS and Pool-Frenkel emission in the HRS, respectively. To expand this area of study into flexible electronics, the plastic film, polyethersulfone (PES), was adopted as a flexible substrate of the transparent memory. We prepared a transparent and flexible resistive random access memory (TFRRAM) device on a PES at room temperature. To avoid the delaminating phenomena of ITO/PES film occurred at successive bending tests of the TFRRAM device, a special ITO/Ag/ITO multi-layered structure was employed as a bottom electrode. This multi-layered electrode played important roles as highly transparent electrode as well as mechanically ductile layer. Therefore, the TFRRAM device showed not only high transparency (~ 80 %) in visible region, but also superior flexibility performance due to the ITO/Ag/ITO multi-layered electrode. Excellent nonvolatile resistive switching characteristics and reliable data retention propert...