Fabrication of Epitaxial W‑Doped VO2 Nanostructured Films for Terahertz Modulation Using the Solvothermal Process

• Published in: ACS applied nano materials 2021-10, Vol.4 (10), p.10592-10600
• Main Authors: Ivanov, Alexey V, Tatarenko, Artem Yu, Gorodetsky, Andrei A, Makarevich, Olga N, Navarro-Cía, Miguel, Makarevich, Artem M, Kaul, Andrey R, Eliseev, Andrei A, Boytsova, Olga V
• Format: Article
• Language: English
• ISSN: 2574-0970; 2574-0970
• DOI: 10.1021/acsanm.1c02081

We report a feasible and high-throughput method for high-quality W-doped VO2 nanostructured epitaxial films on r-sapphire substrate fabrication. Single-phase, smooth vanadium dioxide thin films with uniform distribution of tungsten (up to 2.3%) are formed using the solvothermal process from ethylene glycol/water V4+ and W6+ solutions. Compositional analysis by X-ray photoelectron and energy-dispersive X-ray spectroscopy (XPS and EDX, respectively); structural analysis (X-ray diffraction, Raman spectroscopy, selected area electron diffraction (SAED)); and detailed analysis of the surface morphology and substrate–film interface using scanning electron microscopy, atomic force microscopy, and high-resolution transmission electron microscopy (SEM, AFM, HRTEM, respectively) confirm the formation of nanoscale (50–60 nm) epitaxial W:VO2 (M1) on r-sapphire with epitaxial relationships (100)­VO2∥(101̅2)­Al2O3 and [010]­VO2∥[011̅0]­Al2O3. The nanostructured films demonstrate excellent terahertz (THz) transmission properties: a phase transition temperature of 31 °C, a huge THz modulation depth of over 60%, and broad bandwidth (≥2 THz) operation. Hence, they can be efficiently used as active material for tunable THz manipulation devices.