Vanadium Dioxide\nby Atomic Layer Deposition: A Promising\nMaterial for Next-Generation Memory Devices

The synthesis of a vanadium dioxide (VO<sub>2</sub>)\nfilm using\natomic layer deposition (ALD) with vanadium tetrachloride (VCl<sub>4</sub>) as a precursor for the realization of programmable memory\ndevices is reported. X-ray diffraction analysis revealed the epitaxial\ngrowth of VO<sub>2</sub> on c-Al<sub>2</sub>O<sub>3</sub>. The phase\ntransition was monitored using resistivity measurements across varying\ntemperatures, demonstrating a decrease of >4 orders of magnitude\nat\nthe transition temperature, thereby confirming the high quality of\nthe material. From this material, memristive devices are fabricated\nas resistive random-access memory (RRAM). On the basis of spiking\nvoltage inputs, these RRAM exhibited cycle stability over 512 cycles\nand state retention stability for >450 s, showing <2% drift.\nWith\nrespect to synaptic-like applications, the RRAM devices were piloted\nthrough step patterns to enable multilevel memory states. These ALD-grown\nVO<sub>2</sub>-based devices demonstrate potential for use as synaptic\nconnections with multiweight synapses, advancing scalability in neuromorphic\napplications.