Microwave Characterization of BST Thin Films on LAO Interdigital Capacitor

Cheng, Y. L.; Chong, Nui; Wang, Yu; Liu, J. Z.; Chan, H.L.W.; Choy, C. L.

doi:10.1080/10584580390259407

Cited by 7 publications

(2 citation statements)

References 3 publications

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“…The dielectric constant based on measurement frequency ranges was almost unchanged. These results corresponded to the report of Cheng et al 19) The Curie temperature profile of the (Ba 0:6 Sr 0:4 )TiO 3 ceramic sintered above 1400 C showed a narrow curve. 20) However, the transition of the dielectric constant broadens with the increase in Ge concentration.…”

Section: Resultssupporting

confidence: 92%

Improved Dielectric Properties of Low-Temperature-Sintered (Ba,Sr)TiO₃-Based Ceramics by Ge Substitution

Yoon

Jeong

et al. 2010

Jpn. J. Appl. Phys.

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Multilayer microwave dielectric materials with low sintering temperature are required for microwave phase shifters, filters, and true-time delay devices. We investigated the sintering and dielectric properties of (Ba0.6Sr0.4)(Ti1-x Ge x )O3 (BSTG; 0.05≤x≤0.3) ceramics. As the Ge concentration was increased, the lattice constant of BSTG ceramics decreased, and Ba2Ge2TiO8, which is the liquid phase at low temperature, was formed. Ba2Ge2TiO8 liquid phase may increase the sintering density. The effect of Ge substitution is the decrease in the sintering temperature from over 1400 to 1150 °C in BST system ferroelectric ceramics. With increasing Ge concentration, the dielectric constant decreased from 2190 to 530, and the dielectric loss decreased up to 0.001 (at 1 MHz) with sintering at 1150 °C for 2 h. When Ge was substituted at 0.05 and 0.1 mol of Ti in the BST at 1150 °C, the dielectric constant, dielectric loss, tunability, Curie temperature, and figure of merit were 2184 and 1529, 0.002 and 0.001, 27 and 23%, -11 and -18 °C, and 135 and 230, respectively. These compositions show microwave dielectric properties comparable to those of (Ba0.5Sr0.5)TiO3 ferroelectrics, which are the important materials for tunable devices such as varactors, phase shifters, and frequency agile filters.

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Section: Resultssupporting

confidence: 92%

Improved Dielectric Properties of Low-Temperature-Sintered (Ba,Sr)TiO₃-Based Ceramics by Ge Substitution

Yoon

Jeong

et al. 2010

Jpn. J. Appl. Phys.

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“…1, or as planar interdigital capacitors (IDC) [20], [21]. For the parallel plate capacitor the ferroelectric film of height is located between the two metal electrodes.…”

Section: Ferroelectric Thin-film Varactorsmentioning

confidence: 99%

Reduced Size Frequency Agile Microwave Circuits Using Ferroelectric Thin-Film Varactors

Lourandakis

Schmidt²,

Seitz³

et al. 2008

IEEE Trans. Microwave Theory Techn.

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A new concept for tunable and reduced size microwave circuits is presented based on barium-strontium-titanate (BST) varactors. The proposed design methodology relies on substitution of quarter-wavelength transmission line segments with their equivalent low-pass structures. The ferroelectric BST-varactors are used as tuning elements and allow for a frequency agile behavior and size reduction of the circuit. Candidates for this methodology are quarter-wavelength based circuits such as Wilkinson power dividers and branch-line couplers. Prototype boards for both topologies were implemented and characterized through scattering parameter measurements. For the implemented Wilkinson divider a tuning range from 1.7 to 2.1 GHz is achieved. The insertion loss in both output paths varies from 0.6 to 1.2 dB while maintaining a worst case amplitude-and phase difference of 0.5 dB and 9 , respectively, for all operating cases. The isolation between the two output ports exceeded 25 dB over the whole tuning range. The implemented branch-line coupler exhibits a tuning range from 1.8 to 2.3 GHz with a maximum insertion loss of 2.7 dB while maintaining worst case amplitudeand phase difference of 0.4 dB and 90 5 , respectively. Port matching and isolation levels of more than 15 dB are exhibited at all bias conditions. Index Terms-Couplers, ferroelectric capacitors, power dividers, tunable circuits and devices.

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Microwave characterization of (Pb,La)TiO3 thin films integrated on ZrO2∕SiO2∕Si wafers by sol-gel techniques

Song

Wang

Chan

et al. 2004

Applied Physics Letters

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Polycrystalline perovskite lead lanthanum titanate (PLT) thin films were prepared by a sol-gel method on ZrO 2 / SiO 2 / Si substrates. The structure of the films was studied by x-ray diffraction and scanning electron microscopy, and the microwave dielectric properties characterized on a network analyzer. A strong dependence of the dielectric constant of PLT films and, correspondingly, the resonance frequency of PLT-based interdigital capacitor on the sample preparation conditions were observed. They resulted from the structural transformation of PLT from a layered structure to a uniform film as the annealing temperature was raised from 550 to 700°C, suggesting a possible way to modify the device performance by controlling the layered structure of the ferroelectric While many of the ferroelectric/piezoelectric thin filmbased devices may work at relatively low frequencies (usually at megahertz or lower), in recent years ferroelectric and piezoelectric devices working at higher frequencies [up to gigahertz (GHz)] have also attracted strong interest. Typical examples of such devices include microwave phase shifters and piezoelectric film-based biosensors for DNA and protein tests. [1][2][3][4][5][6] Around the GHz range, the ferroelectric domains usually cannot switch fast enough to keep up with the external ac field; consequently, the dielectric behaviors of the ferroelectrics are dramatically different from their low frequency dielectric properties. The microwave characterization of ferroelectric thin films is of significance both for fundamental understandings and practical applications. Technically, the high frequency dielectric measurement of ferroelectric films remains a challenge despite continued research efforts in the last few decades on the development of various testing techniques and theoretical models for solving the technical problems. This may be the reason for the lack of microwave characterization of many typical ferroelectric thin films, even though barium strontium titanate films, as a candidate for tunable microwave devices, have been extensively studied in the last decade. [7][8][9] In this letter, the dielectric properties of lanthanumdoped lead titanate [nominal composition as ͑Pb 0.85 La 0.10 ͒TiO 3 (PLT)] thin films integrated on buffered silicon were investigated at high frequencies up to the GHz range. PLT is a very useful ferroelectric material that can be used for infrared micro-sensors, ferroelectric memories, electro-optical devices, and piezoelectric micro-sensors (for biological applications). [10][11][12][13][14][15] The structural development and control, ferroelectric behavior, pyroelectric performance, and piezoelectric properties of PLT have been extensively studied in the literature. The samples for tests have a layered structure: PLT film/ ZrO 2 / SiO 2 / Si. Both ZrO 2 and SiO 2 are the buffer layers. The sample preparation was basically a multistep microfabrication process. On a (100)-oriented silicon wafer with a 5.46 m thermally grown SiO 2 layer, ZrO 2 film (200 nm thic...

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Microwave Characterization of BST Thin Films on LAO Interdigital Capacitor

Cited by 7 publications

References 3 publications

Improved Dielectric Properties of Low-Temperature-Sintered (Ba,Sr)TiO₃-Based Ceramics by Ge Substitution

Improved Dielectric Properties of Low-Temperature-Sintered (Ba,Sr)TiO₃-Based Ceramics by Ge Substitution

Reduced Size Frequency Agile Microwave Circuits Using Ferroelectric Thin-Film Varactors

Microwave characterization of (Pb,La)TiO3 thin films integrated on ZrO2∕SiO2∕Si wafers by sol-gel techniques

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Microwave Characterization of BST Thin Films on LAO Interdigital Capacitor

Cited by 7 publications

References 3 publications

Improved Dielectric Properties of Low-Temperature-Sintered (Ba,Sr)TiO3-Based Ceramics by Ge Substitution

Improved Dielectric Properties of Low-Temperature-Sintered (Ba,Sr)TiO3-Based Ceramics by Ge Substitution

Reduced Size Frequency Agile Microwave Circuits Using Ferroelectric Thin-Film Varactors

Microwave characterization of (Pb,La)TiO3 thin films integrated on ZrO2∕SiO2∕Si wafers by sol-gel techniques

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Product

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Improved Dielectric Properties of Low-Temperature-Sintered (Ba,Sr)TiO₃-Based Ceramics by Ge Substitution

Improved Dielectric Properties of Low-Temperature-Sintered (Ba,Sr)TiO₃-Based Ceramics by Ge Substitution