Memory effect of vertically stacked hBN/QDs/hBN structures based on quantum-dot monolayers sandwiched between hexagonal boron nitride layer

摘要

The characteristics of a flexible write-once-read-many-times (WORM) memory fabricated with monolayered 0dimensional (0D) CdSe-ZnS quantum dots (QDs) layers sandwiched between two insulating 2-dimensional (2D) hexagonal boron nitride (hBN) multilayers were investigated by electrical measurement method. The hBN/QDs monolayer/hBN structure was fabricated in a vertical stacked structure using a technique which control the formation of the QDs monolayer. QDs monolayer was formed by electrostatic interaction between the negative charge group on the CdSe-ZnS QDs surface and the positive charge group on the hBN surface. The device has a WORM characteristic due to the presence of QDs in the current-voltage (I-V) measurement. When a bias is applied, carriers were initially trapped by tunneling due to the QDs and then a conductive filament was formed in the hBN, which were not detrapped and exhibit characteristics of write-once-read-many-times memory. The maximum ON/OFF ratio of the current for the devices was as large as 4 x 10, and the endurance was 5 x 104 cycles, and a retention time was larger than 1 x 105 s. In order to explain the carrier transport mechanism and conductive filament of the WORM memory device caused by QDs, it through various methods such as I-V fitting data, simulation, and conductive AFM. Unlike the conventional conductive filament mechanism, through random diffusion such as Ag filament, the Au/hBN/QD/hBN/ITO/PET structures implemented a consistent conductive filament using Au metal and QDs active layer.