Enhancement of Pt/a‐Si/Cu/a‐Si/Pt Microwave/Sub‐Terahertz Resonators as Negative Capacitance Sources, Frequency Stabilizers, and DCS1800 Quad‐Band Filters via Cu Nanosheets

Herein, stacked layer of amorphous silicon (a‐Si) comprising copper nanosheets of different thicknesses (50–150 nm) are fabricated to perform as high‐frequency resonators. The impedance spectroscopy analyses which were carried out in the carrier frequency range of 0.01–1.8 GHz on amorphous Pt/a‐Si/Cu/a‐Si/Pt (PSCS) stack showed their controllable resonator characteristics by varying Cu nanosheets thickness. Thicker Cu layers resulted in the negative capacitance effect and domination of correlated barrier hopping over quantum mechanical tunneling. While thin Cu layers of thickness of 50 nm increased the cutoff frequency ( f co ) to 11 GHz, thicker samples exhibited positive and negative f co values that reaches 0.30 THz indicating the ability of the PSCS resonators to work in the subterahertz range as resonators and frequency stabilizers. In addition, practical tests on the PSCS devices as band filters have shown the perfect performance of the device as digital cellular systems DCS1800 and long term evolution LTE (5G) systems. The magnitude of the reflection coefficient, the return loss value, and the voltage standing wave ratios at the quad‐band frequency of 1.80 GHz reached values of 0.025, 31.8 dB, and 1.05, respectively, nominating them for applications as high‐frequency and global system of mobile communications.