Atomic Layer Deposition of Transparent VOx Thin Films for Resistive Switching Applications†

Atomic layer deposition (ALD) offers nearly pinhole-free, conformal, and with good thickness control, metal oxide nanometric thin films required for next-generation memory devices. Here we report on the ALD of VO_x thin films grown at about 100°C from a vanadium tri-isopropoxide (VTIP) precursor, with water as the co-reactant, followed by their post-growth treatments, for potential applications in resistive switching (RS) devices. As-grown VO_x films are amorphous, and transform into polycrystalline layers upon annealing. Capacitor structures fabricated from amorphous VO_x films show current-voltage (I-V) characteristics, interesting for RS applications. Depending on the electroforming conditions, bipolar-type memory switching with a resistance ratio R_OFF/R_ON > 10³ is obtained, as well as a combination of memory and threshold switching. The latter is attractive for its highly non-linear I-V characteristics, which is attributed to the temperature-induced insulator-to-metal transition (IMT) in vanadium dioxide.