The prospects of using ferroelectrics thin films for the farbrication and development of frequency and phase agile microwave devices have increased in past few years due to improvenebts in ferroelectric thin film processing techniaues as well as innovative circuit design. In microwave devices, ferroelectric thin film is used as tuning layer through the electric field dependence of the relative dielectric constant.
Typical paraelectric materials ($SrTiO_3, KTaO_3, Ba Sr_1 TiO_3$) and electrically tunable microwave devices based on these materials shows that in spite of the recent year`s extensive efforts, no considerable improvement in the microwave losses in thin paraelectric films has been achieved. Thin films, regardless of fabrication method and substrate type, have much lower dielectric permittivity than bulk single crystals, and the loss tangent at microwave frequencies (10 GHz) is of the order of 0.01 (at zero dc-bias field) at room temperature. Nevertheless, quite promising component and subsystem level devices are successfully demonstrated. Use of ceramic (bulk and thick film) ferroelectrics in tunable microwave devices, currently considered for industrial applications, offer cost reduction. In this paper, explicitly for the first time, we consider possibilities and benefits of using ferroelectrics in polar phase in electrically controllable microwave devices. Examples of using ferroelectrics in polar state (e.g., Na0 5K0 5NbO3, SrTiO3 in antiferroelectric phase) in electrically tunable devices are reported. Index Terms-Ferroelectrics, paraelectrics, tunable microwave devices. This trends demand the researches about ferroelectric material with polar phase in microwave frequency.
In this study, typical ferroelectric material, $BaTiO_3$ thin films with polar phase were observed dielectric properties in microwave frequency.
In this study, typical ferroelectric material, $BaTiO_3$ this films with polar phase were observed dielectirc properties in microwave frequency. $BaTiO_3$ thin films were epitaxially grown on $LaAlO_3$ substrates by RF magnetron sputtering system of a stoichiometric, high- density, ceramic target. X-ray diffraction analysis showed c-axis oriented cube-on cube growth. Micrometer size interdigital capacitor (IDT) structures were defined on surface the BT film using photolithography. The electrical characterization at 10GHz showed dissipation factor tan δ of 0.18, tunability 1.5% applied bias voltage 15V. The capacitance and tan δ were showed to remain stably from 500 MHz to 10 GHz. The results showed abilities improved to apply for tunable microwave devices based on ferroelectric BT thin film
