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Epitaxial layered Sb2Te3 thin films for memory and neuromorphic applications

Two-dimensional layered materials have attracted a lot of attention as building block in memristive devices owing to their high downscaling potential, easy stacking due to van der Waals forces and mechanical flexibility. In this study, memristive switching is explored in vertical device structures based on layered Sb2Te3. For this, epitaxial 2D-like Sb2Te3 thin films with thicknesses of ∼20 nm were directly grown on conductive p-type Si (111) substrates by pulsed laser deposition. Analog programmability mimicking neuromorphic operation, stable multilevel retention and endurance performance with a memory window larger than one order of magnitude are achieved by utilizing Ag as electrode metal. However, Cu top electrodes lead to a memristive switching with generally smaller memory window and volatility of programmed states. Devices with both electrode metals offer forming-free operation and self-compliance. Structural and chemical characterization reveal a diffusion of Ag and Cu into the Sb2Te3. It is suggested that charge trapping is involved in the memristive switching mechanism. Overall, this work shows the high potential of thin layered Sb2Te3 for neuromorphic computing and offers a scalable method for integration into the existing Si platform.