Electrical Characterizations of Paraelectric BST Thin Films up to 1 THz: Realization of Microwave Phaseshifters

Abstract

BST thin films have been deposited with a sol-gel technique on 4cm 2 sapphire. Electrical characterizations have been performed in a very large frequency range. From 1 kHz to 500 GHz, the dielectric constant ϵ r is around 300 with quasi no frequency dispersion. In the 500 GHz to 1 THz range, the existence of a Debye relaxation mode is postulated. Varactors made with these BST films show a decrease of their capacitance by a factor of about 1.7 under 40 volts of bias. Phaseshifters have been realized with these varactors: a bias of 40 volts at 30 GHz permits to obtain a phaseshift of 360 degrees.