Interface engineering for integration of VO2 on silicon for thermotronics
Résumé
Present day information processing is the result of the development of the microelectronics industry where information is processed via electrical currents and voltages. Unlike its electronic counterparts, thermal information processing (thermotronics) via radiative heat flow through thermal analogs of transistors remains a nascent technology. In order to achieve this, we use a phase change material, vanadium dioxide (VO2), and exploit its non-linear change of optical properties as a function of its temperature. VO2 undergoes a metal-insulator transition (MIT) at approximately 70°C, which induces large variations in its electrical and wavelength-dependent optical properties. These features make VO2 a highly sought-after compound for optical, thermal, and neuromorphic applications1. To foster the development of VO2-based devices for the microelectronic industry, it is also imperative to integrate VO2 on silicon. However, high lattice mismatch and the formation of silicates at the interface between VO2 and Si degrade the quality and functionality of VO2 films. Moreover, VO2's polymorphic nature and stable V-O phases pose integration issues. To address these challenges, we investigate the MIT of VO2 thin films integrated on Si with a HfZrO2 (HZO) buffer layer. We demonstrate that VO2 on HZO buffer layer exhibits an unusually low thermal hysteresis of ~4 °C2. These results unravel the influence of strain on M2 phase nucleation, which controls the hysteresis. Notably, the rate of phase transition is symmetric and does not change for the heating and cooling cycles, implying no incorporation of defects during cycling, and highlighting the potential HZO for VO2 based devices reliable operation. References: [1] P. J. van Zwol, K. Joulain, P. Ben-Abdallah, J. Chevrier, Phys. Rev. B 84, 161413 (2011). [2] Swayam Prakash Sahoo, Matthieu Bugnet, Ingrid Cañero Infante, Victor Pierron, Laurence Méchin, et al. Small Science, 2400398 (2024).