Pulsed Laser and Atomic Layer Deposition of CMOS-Compatible Vanadium Dioxide: Enabling Ultrathin Phase-Change Films.

Vanadium dioxide (VO), a well-known Mott insulator, is a highly studied electronic material with promising applications in information processing and storage, including neuromorphic and brain-inspired electronics, high-frequency reconfigurable electronics, optoelectronic modulators, sensors, and smart windows with thermal regulation. While epitaxial VO layers exhibit exceptional properties, such as a sharp and abrupt conductivity change at the metal-insulator transition, fabricating polycrystalline VO films on silicon substrates often involves trade-offs in transport characteristics and switching performance, especially for ultrathin layers required in advanced gate applications. In this study, we explore the growth dynamics of VO films on standard CMOS-compatible wet-oxidized silicon wafers by using two established deposition techniques: pulsed laser deposition (PLD) and atomic layer deposition (ALD). VO films, ranging in thickness from 200 nm to less than 10 nm, were systematically characterized through structural and electrical analyses to optimize key growth parameters. In this study, the temperature and pressure were identified as the key factors influencing the morphology and quality of switching in VO2 films. The growth dynamics and optimal growth conditions across the entire thickness range are discussed in detail. PLD and ALD offer distinct advantages: PLD enables the formation of high-density films, while ALD allows for conformal deposition on complex 3D structures. We demonstrate that both methods can successfully produce ultrathin VO layers down to 6-8 nm with functional properties suitable for practical applications, provided that growth parameters are carefully optimized. This work underscores the potential of VO for fully CMOS-compatible phase-change switching devices and provides valuable insights into optimizing growth processes for polycrystalline VO films grown with different techniques, including widely used magnetron sputtering.