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Proceedings of Conferences

Session 3 "Ferroelectrics at Microwaves"

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	Patterning of tunable device based on ferroelectric thin film multilayer (170.17 Kbytes) hot!	2004-06-29
Patterning of tunable device based on ferroelectric thin film multilayer H. I. Chien, K. Sarma, R. Walters, P. K. Petrov, N. McN. Alford Physical Electronic and Material Center, Faculty of Engineering, London South Bank University, 103 Borough Road, SE1 0AA, UK. E-mail: chienhi@lsbu.ac.uk Website: http://www.eeie.lsbu.ac.uk/research/pem/index.html Introduction Ba-Sr-Ti-O thin films are promising candidates for making microwave tunable device due to their ability to change their permittivity under applied electrical field [1, 2]. The performances of these tunable devices depend on the materials and electrodes [3]. And it is believed that if it were possible to produce thicker electrodes then any adverse effect on the performance would be negligible. Therefore the purpose of this study was to produce a structure with different electrode thickness by using the lift-off method [4]. Thereafter, the aim is to analyze the performance of the device.
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	The influence of synthesis temperature on structure properties of BaXSr1-XTiO3 ferroelectric films (149.8 Kbytes) hot!	2004-06-29
The influence of synthesis temperature on structure properties of Ba_XSr_1-XTiO₃ ferroelectric films A. K. Mikhailov, A. V. Tumarkin, and S. V. Razumov Dept. of Electronics, St.-Peterburg Electrotechnical University, 5 Prof. Popov st., 197376, St.-Peterburg, Russia Abstract – The results of structure investigations of (Ba,Sr)TiO₃ films depending on synthesis temperature are presented. Electrical characteristics of planar capacitors based on prepared films are investigated. Finally, the technological conditions of high structure quality (Ba,Sr)TiO₃ films preparation are determined. (Ba,Sr)TiO₃ films prepared under those conditions possess electrical characteristics sufficient for room temperature microwave applications in a wide frequency range.
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	Intrinsic and extrinsic dielectric loss mechanisms in ferroelectric thin films at microwave frequencies (175.51 Kbytes) hot!	2004-06-29
Intrinsic and extrinsic dielectric loss mechanisms in ferroelectric thin films at microwave frequencies K. F. Astafiev, V. O. Sherman, A. K. Tagantsev, and N. Setter Ceramics Laboratory, Swiss Federal Institute of Technology, EPFL, CH-1015 Lausanne, Switzerland. Abstract – The dc bias field dependence of the dielectric loss in SrTiO₃ thin films deposited onto MgO substrate is investigated. The experimental data obtained at different frequencies of the ac field (8 and 16 GHz) from differently processed films (as deposited and oxygen-annealed) strongly suggest the occurrence of a crossover in the dominating loss mechanism. The crossover is driven by the dc bias field: at weak fields the loss is governed by an extrinsic mechanism(s) whereas, at higher fields, the contribution of an intrinsic mechanism (dc field-induced quasi-Debye loss) becomes predominant.
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	The temperature dependence of the capacitance of a planar capacitor containing layered BSTO structur (141.98 Kbytes) hot!	2004-06-29
The temperature dependence of the capacitance of a planar capacitor containing layered BSTO structures N. U. Nekrasova Dept. of Electronics, St.-Petersburg Electrotechnical University, 5 Prof. Popov st., 197376, St. Petersburg, Russia Introduction The dielectric nonlinearity of ferroelectrics makes it possible to elaborate electrically tunable microwave devices and components. Ba_xSr_1-xTiO₃ (BSTO) is a typical ferroelectric material suitable for microwave application at room temperature [1]. According to the theory of ferroelectricity, the temperature dependence of the dielectric permittivity ε(T) of a homogeneous BSTO sample obeys the Curie-Weiss law [2]. The measurements of BSTO planar capacitors revealed that the observed experimental temperature dependence ε(T) did not follow this law. In order to explain this anomalous behavior of the capacitance, it is supposed that the investigated BSTO films consist of layers with different phase transition temperatures, which correspond to the different barium concentration across the BSTO film profile.
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	Dielectric losses of thin BaXSr1-XTiO3 films depending on sputtered atoms flux rate (142.46 Kbytes) hot!	2004-06-29
Dielectric losses of thin Ba_XSr_1-XTiO₃ films depending on sputtered atoms flux rate O. V. Skobyak, A. V. Tumarkin and S. V. Razumov Dept. of Electronics, St.-Peterburg Electrotechnical University, 5 Prof. Popov st., 197376, St.-Peterburg, Russia Abstract – The influence of sputtered atoms flux rate on loss factor of planar varactors based on ion-plasma deposited BaSrTiO₃ films is investigated. Planar capacitors with copper electrodes were used for investigation of the tunability and loss factor. Microwave characteristics of varactors based on BaSrTiO₃ films were measured at frequency 1 GHz and temperature 300 K. The films grown with step-by-step increasing of discharge power value that corresponds to increasing the sputtered atoms flux rate exhibit low loss and a suitable tunability.
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