Abstract
Tunable ferroelectric capacitors, which exhibit a decrease in the dielectric permittivity under an electric field, are widely used in electronics for RF tunable applications. Current devices use barium strontium titanate (BST) as the tunable dielectric, but new applications call for tunable materials with specific performance improvements. It is then of crucial importance to dispose of a large panel of electrically characterized materials to identify the most suited compound for a given set of device specifications. Here, we report on the dielectric tuning properties of Ba1−xCaxTi1−yZryO3 (BCTZ) thin films libraries (0 ≤ x ≤ 30% and 0 ≤ y ≤ 28.5%) synthesized by combinatorial pulsed laser deposition (CPLD). An original CPLD approach allowing reliable and statistical ternary phase diagrams exploration is reported. The effects of Ca and Zr content on tunability, breakdown voltage and dielectric losses are explicated and shown to be beneficial up to a certain amount. Compounds close to (Ba0.84Ca0.16)(Ti0.8Zr0.2)O3 exhibit the highest figures of merit, while a zone with compositions around (Ba0.91Ca0.09)(Ti0.81Zr0.19)O3 show the best compromise between tuning ratio and figure of merit. These results highlight the potential of BCTZ thin films for electrically tunable applications.
Highlights
Accepted: 1 September 2021Ferroelectric (FE)-perovskite-films-based heterostructures are found in many microelectronic components dedicated to RF and microwave (MW) applications thanks to the large electric field dependence of the relative dielectric permittivity εr (E) near the Curie temperature TC [1]
For Near Field Communications (NFC) technology, the operating voltage is reduced to a 0–3 V range compared to 0–24 V for actual tunable capacitor products in mobile phone application [3], resulting in a lowered electric field and tunability
We explored a part of the BCTZ phase diagram using an original 3 targets combinatorial pulsed laser deposition (CPLD)
Summary
Accepted: 1 September 2021Ferroelectric (FE)-perovskite-films-based heterostructures are found in many microelectronic components dedicated to RF and microwave (MW) applications thanks to the large electric field dependence of the relative dielectric permittivity εr (E) near the Curie temperature TC [1]. The solid solution Ba1−x Srx TiO3 (BST) is the most used FE material in nowadays RF and MW tunable capacitors because of its excellent tunability/losses compromise and adjustable. Emerging technologies call for improved tunable capacitor properties. For Near Field Communications (NFC) technology, the operating voltage is reduced to a 0–3 V range compared to 0–24 V for actual tunable capacitor products in mobile phone application [3], resulting in a lowered electric field and tunability. For a given application with a defined operating window (maximum applicable voltage, temperature range, minimum filters quality factor and Figure of Merit from circuit design), one has to seek for the FE material with the best compromise between various properties (tunability, dielectric losses, temperature coefficient TC).
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