Compositional-gradient [Formula: see text][Formula: see text]O3 thin films on Pt(100)/Ti/SiO2/Si substrates are fabricated with sol–gel using spin coating. All of the structures of the prepared thin films are of single-phase crystalline perovskite with a dense and crack-free surface morphology. BTS10/15/20 thin film exhibits enhanced temperature stability in its dielectric behavior. The temperature coefficient of capacitance [Formula: see text] in the temperature range from [Formula: see text]C to [Formula: see text]C is [Formula: see text]C and that of [Formula: see text] in the temperature range from [Formula: see text]C to [Formula: see text]C is [Formula: see text]C. Furthermore, the thin films show low leakage current density and dielectric loss. High and stable dielectric tunable performances are found in BTS10/15/20 thin films: the dielectric tunability of the thin films is around 20.1% under a bias voltage of 8 V at 1 MHz and the corresponding dielectric constant is in the range between 89 and 111, which is beneficial for impedance matching in circuits. Dielectric tunability can be obtained under a low tuning voltage, which helps ensure safety. The simulated resonant frequency of the compositional-gradient BTS thin films depends on the bias electric field, showing compositional-gradient BTS thin films could be used in electrically tunable components and devices. These properties make compositional-gradient BTS thin films a promising candidate for dielectric tuning.
We fabricate BaTi0.85Sn0.15O3 thin films with various Ca doping contents on Pt(100)/Ti/SiO2/Si substrates by a sol-gel and spin-coating method to investigate the effects on dielectric tunable properties. The results show that the greater tunability under a low bias electric field can be achieved compared with undoped BaTi0.85Sn0.15O3 thin films. In particular, the 0.1 mol. % Ca-doped BaTi0.85Sn0.15O3 thin films achieve the highest tunability of 50.9% and the highest FOM value of 23.1 at 16 kV/mm, surpassing most values reported previously for the dielectric tunability of BTS thin films. The use of a low bias electric field avoids the need for a high voltage, thus reducing safety hazards. These outstanding properties are attributed to the broadening of the Curie peak near room temperature, which indicates the existence of diffuse ferroelectric phase transition behavior, a larger grain size, and the suppression of electron hopping between Sn2+ and Sn4+. The results show the great potential of Ca-doped BaTi0.85Sn0.15O3 thin films for dielectric tunable applications.
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