Impacts of growth oxygen pressure and laser fluence on microwave tunings of Ba0.8Sr0.2TiO3 thin films

The impacts of growth oxygen pressure and laser energy in the pulsed laser deposition on the structural, chemical, and electrical properties of Ba0.8Sr0.2TiO3 ferroelectric thin films were investigated. The relative Ba: Sr: Ti ratio in the films was correlated with the capacitance C–voltage V tuning characteristics for the application of microwave tunable capacitors. An enhanced C–V tunability higher than 4:1 was obtained at 1.2 J/cm2 and 40 mTorr and the quality factor Q exhibited resonant pattern as functions of frequency (1–10 GHz) and applied electric field (0–233 kV/cm). Second-order microwave filters were derived from the interdigital capacitor covering the microwave L (1–2 GHz), S (2–4 GHz), and C (4–8 GHz) bands.