VO2 Thin Film as a Temperature Activated Electromagnetic Shield

This communication presents the fabrication, characterization and performance of a vanadium dioxide (VO2) thin film deposited on a c-cut sapphire substrate, and used as an electromagnetic screen whose shielding effectiveness is controlled through heating/cooling. The film is first deposited at high temperature on the substrate using a radiofrequency magnetron sputtering technique, and is then annealed in-situ in pure dioxygen atmosphere, to obtain the required oxide stoichiometry. The screen shielding effectiveness is measured using the nested reverberation chamber method at room temperature and at 75 degrees C. At 65 degrees C, VO2 undergoes an insulator to metal transition and the material conductivity drastically increases, resulting in a significant shielding effect of the VO2 layer at microwaves (2 - 34 GHz). The experimental results are in accordance with theoretical values predicted by an analytical model. The VO2-based electromagnetic shield is therefore a promising solution to protect sensitive electronics from high intensity radiated field by using the temperature rise as the trigger to rapidly improve the shielding effectiveness of the screen. On the contrary, cooling down the screen is possible if shielding is no longer necessary.