Enhanced microwave dielectric tunability of Ba0.5Sr0.5TiO3 thin films grown with reduced strain on DyScO3 substrates by three-step technique (original) (raw)
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Journal of Applied Physics, 2010
Dielectric properties of annealed and as-grown ferroelectric Ba 0.5 Sr 0.5 TiO 3 ͑BST͒ grown by pulsed laser deposition on sputtered BST seed layers on strontium titanate ͑STO͒ substrates were investigated at microwave frequencies in the realm of tunability of its dielectric constant as well as phase shifters based on this material. The as-grown layers were nearly fully relaxed with measured lattice parameters nearly identical to those of bulk BST. The tuning of the relative dielectric constant ͑ϳ1750 at zero bias at 10 GHz͒ of the annealed BST was found to be as high as 59% and 56% at 10 and 19 GHz, respectively. The analysis of the loss in the BST results in a measured tan ␦ of 0.
Journal of Applied Physics, 2010
Dielectric properties of annealed and as-grown ferroelectric Ba0.5Sr0.5TiO3 (BST) grown by pulsed laser deposition on sputtered BST seed layers on strontium titanate (STO) substrates were investigated at microwave frequencies in the realm of tunability of its dielectric constant as well as phase shifters based on this material. The as-grown layers were nearly fully relaxed with measured lattice parameters nearly identical to those of bulk BST. The tuning of the relative dielectric constant (∼1750 at zero bias at 10 GHz) of the annealed BST was found to be as high as 59% and 56% at 10 and 19 GHz, respectively. The analysis of the loss in the BST results in a measured tan δ of 0.02 for the annealed as well as the unannealed films at a frequency of 18 GHz. Phase shifters also exhibited high tuning with differential phase shift figures of merit of 35 and 55°/dB at a field of 60 kV/cm at 10 and 19 GHz, respectively. Serendipitously, most of the tuning occurs at low fields, and thus we pr...
Journal of Advanced Dielectrics, 2015
Ba(Mg[Formula: see text]Nb[Formula: see text]O3 (BMN) doped and undoped Ba[Formula: see text]Sr[Formula: see text]TiO3 (BST) thin films were deposited via radio frequency magnetron sputtering on Pt/TiO2/SiO2/Al2O3 substrates. The surface morphology and chemical state analyses of the films have shown that the BMN doped BST film has a smoother surface with reduced oxygen vacancy, resulting in an improved insulating properties of the BST film. Dielectric tunability, loss, and leakage current (LC) of the undoped and BMN doped BST thin films were studied. The BMN dopant has remarkably reduced the dielectric loss ([Formula: see text]38%) with no significant effect on the tunability of the BST film, leading to an increase in figure of merit (FOM). This is attributed to the opposing behavior of large Mg[Formula: see text] whose detrimental effect on tunability is partially compensated by small Nb[Formula: see text] as the two substitute Ti[Formula: see text] in the BST. The coupling between...
High tunability in lead-free Ba0.85Sr0.15TiO3thick films for microwave tunable applications
Ceramics International, 2019
Lead free ferroelectric Ba0.85Sr0.15TiO3(BST)thick films were successfully deposited by screen printing process on Ag-Pd/Al2O3 substrates. The microstructure of the samples was analyzed by scanning electron microscope (SEM)and X-ray diffraction (XRD). The thick films showed a good adhesion to the Ag-Pd/Al2O3 substrate, a porous microstructure and uniform thicknessesof about10 µm. The dielectric propertiesofBST thick films were studied over a wide frequency range (10-1 Hz to 10 6 Hz) and in a large temperature range from25 °C to 350 °C. The AC conductivity inBST thick films was systematically investigated.Ferroelectric characterizations and tunability were also studied at room temperature by polarization cycles P(E) andcapacitance C(E) measurements. The high values of dielectric permittivity and tunability (67%) combined with low dielectric loss (tgδ) make Ba0.85Sr0.15TiO3 thick films one of the encouraging candidates for microwave tunable applications.
Journal of Applied Physics, 2004
Al2O3 doped Ba0.5Sr0.5TiO3 (BST) thin films, with different Al2O3 contents, were deposited on (100) LaAlO3 substrate, by pulsed laser deposition (PLD) technique to develop agile thin films for tunable microwave device applications. The dielectric properties of Al2O3 doped BST films were determined with non-destructive dual resonator near 7.7 GHz. The effects of Al2O3 doping are the significant reduction of dielectric constant, dielectric loss and tunability, compared with pure BST thin film. The figure of merit for Al2O3 doped BST films have also been shown to increase with Al2O3 content. Consequently, Al2O3 doped BST films have the potential to be exploited in tunable microwave device applications.
Ferroelectric BaTiO3/SrTiO3 multilayered thin films for room-temperature tunable microwave elements
Nanoscale research letters, 2013
Ferroelectric BaTiO3/SrTiO3 with optimized c-axis-oriented multilayered thin films were epitaxially fabricated on (001) MgO substrates. The microstructural studies indicate that the in-plane interface relationships between the films as well as the substrate are determined to be (001)SrTiO3//(001)BaTiO3//(001)MgO and [100]SrTiO3//[100]BaTiO3//[100]MgO. The microwave (5 to 18 GHz) dielectric measurements reveal that the multilayered thin films have excellent dielectric properties with large dielectric constant, low dielectric loss, and high dielectric tunability, which suggests that the as-grown ferroelectric multilayered thin films can be developed for room-temperature tunable microwave elements and related device applications.
2010
Perovskite Ba 0.6 Sr 0.4 TiO 3 ͑BST͒ thin films have been grown on Al 2 O 3 ͑0001͒ substrates without/ with inserting an ultrathin TiO x seeding layer by rf magnetron sputtering. X-ray diffraction and pole figure studies reveal that the film with the TiO x layer ͑12-Å-thick͒ is highly oriented along the ͑111͒ direction and exhibits a good in-plane relationship of BST͑111͒ ʈ Al 2 O 3 ͑0001͒. The high frequency dielectric measurements demonstrate that the complex permittivity ͑ = Ј − jЉ͒ is well described by a Curie-von Scheidler dispersion with an exponent of 0.40. The resulting epitaxial BST films show high permittivity ͑ϳ428͒ and tunability ͑ϳ41%, at 300 kV/cm and 40 GHz͒ and their microwave properties ͑1-40 GHz͒ potentially could be made suitable for tunable devices.
Enhanced dielectric properties of SrTiO[sub 3] epitaxial thin film for tunable microwave devices
Applied Physics Letters, 2002
The performance of tunable microwave devices based on heteroepitaxial YBa2Cu3Ox/SrTiO3 films on (001) LaAlO3 substrates has been evaluated. It was ascertained that ``out-of-plane'' SrTiO3 lattice parameter is the relevant factor in determining both device agility and dielectric loss. After high temperature annealing (1100 °C, 1 atm O2), only SrTiO3 layers deposited under low oxygen pressure (~10-5 Torr) show an appreciable