Interaction of electromagnetic waves with VO₂ nanoparticles and films in optical and millimetre wave ranges: Prospective for nano-photonics, nano-antennas, and sensors

Recently great interest in the field of nano-optic is attracted to nano-antennas in both basic and applied research. Nano-antennas are represented by metallic nanoparticles and holes in thin films with arrays of the holes. The usual nano-antennas have fixed functionality, but it will be very interesting to get tunability of nano-antennas controlled by external field. Materials with phase transitions are candidates for the development of tuneable nanoantennas. In this report metal-dielectric phase transition in VO2 micro- and submicron particles, films and holes are studied experimentally and theoretically. The complex dielectric permittivity of VO2 is varied drastically with temperature due to structural phase transition, accompanying metal-insulator transition (MIT) at critical temperature (Tc = 340 K). In this work, VO2 film on glass substrate were prepared and investigated in MM wave range (27–37 GHz). Then submicron holes arrays were formed on VO2 films by FIB milling and their optical Raman spectra were studied. The MM wave response of nanosized VO2 films reveals strong anomalies near MIT. The holes and arrays show strong change of the Raman spectra at the wavelength 530 nm under heating by laser radiation. The optical and MM wave electromagnetic properties of homogeneous VO2 nanospheres embedded in the air are studied theoretically. Size effects on the optical properties of the VO2 nanosphere are investigated. In VO2 nanosphere, converting into metallic phase by heating leads to formation of a localized surface plasmon resonance (LSPR) which red shifts by increasing dimension.