Very large phase shift of microwave signals in a 6 nm Hf _x Zr_{1− x} O₂ ferroelectric at ±3 V

In this letter, we report for the first time very large phase shifts of microwaves in the 1–10 GHz range, in a 1 mm long gold coplanar interdigitated structure deposited over a 6 nm Hf _x Zr_{1− x} O₂ ferroelectric grown directly on a high resistivity silicon substrate. The phase shift is larger than 60° at 1 GHz and 13° at 10 GHz at maximum applied DC voltages of ±3 V, which can be supplied by a simple commercial battery. In this way, we demonstrate experimentally that the new ferroelectrics based on HfO₂ could play an important role in the future development of wireless communication systems for very low power applications. (letter)