Integrating Nanopatterned Ferromagnetic and Ferroelectric Thin Films for Electrically Tunable RF Applications

Tunable radio-frequency (RF) components are pivotal elements in frequency-agile and multifunctional systems. However, there is a technical barrier to achieve miniaturized fully electrically tunable RF components. This paper provides and demonstrates the efficacy of a first unique design methodology in developing fully electrically tunable RF components by integrating ferromagnetic [e.g., permalloy (Py)] and ferroelectric (e.g., lead zirconate titanate) thin-film patterns. Py thin film has been patterned in nanometer scale to improve its ferromagnetic resonance frequency for RF applications. Tunable inductors are developed with the utilization of different thicknesses of Py thin film, which show over 50% increment in inductance and over 4% in tunability with dc current. More tunability can be achieved with multiple layers of Py thin film and optimized thickness. A fully electrically tunable slow-wave RF transmission line with simultaneously variable inductance and capacitance density has been implemented and thoroughly investigated for the first time. The measured results show that a fixed phase shift of 90° can be achieved from 1.5 to 1.85 GHz continuously by applying external dc current from 0 to 200 mA and external dc voltage from 0 to 15 V, respectively.