Transparent and Unipolar Nonvolatile Memory Using 2D Vertically Stacked Layered Double Hydroxide

Various 2D materials have received considerable attention as emerging nanoscale materials for low-power and high-performance electronic and optoelectronic device applications. Among these, layered double hydroxide (LDH)-based nanocomposites are promising materials because of their structural diversity and electronic functionality, which are suitable for photocatalysts, catalytic supports, and charge storage. Here, three Al-based LDHs using different divalent cations (Zn²⁺, Ni²⁺, and Co²⁺) are synthesized, and their electrical characteristics are investigated in the form of a two-terminal Pt/Al-based LDHs/fluorine-doped tin oxide junction structure. Only the ZnAl-LDH junction exhibits a distinct unipolar switching behavior with an ON–OFF ratio of ≈10³ and transmittance of ≈87%; the other junctions (NiAl- and CoAl-LDHs) do not exhibit switching and possess relatively low transparency. This difference is attributed to the relatively vertically stacked ZnAl-LDH layer, which enables the formation of a switching filament through the vertical 2D layer and enhances transparency. The ZnAl-LDH junction has a relatively low trap energy (E_t) of ≈0.1 eV that can decrease the SET voltage as the temperature increases, which can be understood by trap-assisted space-charge-limited conduction with thermal-assisted electron excitation. This study sheds light on the potential use of transparent and self-organized vertical stacked ZnAl-LDH materials as resistive switching devices.