Dielectric Characteristics of a Ferroelectric Phase Shifter with a Thin Amorphous Film

The article considers a study of the frequency responses and the nonlinearity coefficient of a ferroelectric (FE) phase shifter, which is the basis for the operation of phased array antennas. The composition of the barium-strontium titanate film (BaxSr1-xTiO3, BST) with a Ba/Sr ratio of 70/30 corresponded to the FE phase at ambient temperature. Thin amorphous BST films were obtained by RF ion-plasma deposition with a thickness of 57 to 323 nm. Structurally, the device studied was a planar capacitor, and the dielectric constant of the FE film in it was calculated based on the obtained capacitance values using the conformal mapping and partial capacitance methods. The study results have shown that the FE films of this composition have a high nonlinearity coefficient (up to 5.1) and low dielectric loss tangent values (no more than 0.019). Frequency studies of the samples have shown stable values of the dielectric constant, loss factor, and dielectric loss tangent up to a resonant frequency ranging from 122 to 165 MHz. The operating frequency range can be increased by modifying the geometry and electrode deposition technology. Therefore, the use of BST films in the ferroelectric phase is promising, and their amorphous structure can help reduce the cost of phased array antennas.