Hydrofluoric acid-free fabrication of structural reconfigurable metamaterials enabled by VO2

A novel fabrication process for structural reconfigurable metamaterials utilizing phase-transition materials has been reported without using hydrofluoric acid by leveraging the significant volume shrinkage during the phase-transition of VO2. The VO2 film was grown using a pulsed laser deposition technique, demonstrating resistance changes of over four orders of magnitude during the transition, with consistent performance maintained over a year under ambient conditions. Germanium (Ge) was used as the sacrificial layer in this fabrication process, and a dry etching recipe was developed and optimized to achieve isotropic etching of Ge. Experimental results demonstrated that optical, localized, and global thermal control can effectively actuate the fabricated MEMS. This advancement paves the way for a promising, environmentally friendly future with broader THz applications in areas such as radar, communications, and imaging systems.