Browsing by Author "Fragkiadakis, Charalampos"

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    Growth and high frequency characterization of Mn doped sol-gel Pb xSr1-xTiO3 for frequency agile applications
    (American Institute of Physics, 2009-06) Fragkiadakis, Charalampos; Luker, Arne; Wright, Robert V.; Floyd, L.; Kirby, Paul B.
    In pursuit of thin film ferroelectric materials for frequency agile applications that are both easily adapted to large area deposition and also high performance, an investigation has been carried out into sol-gel deposition of 3% Mn doped (Pb0.4Sr0.6)TiO3. Large area capability has been demonstrated by growth of films with good crystallinity and grain structure on 4 in. Si wafers. Metal-insulator-metal capacitors have also been fabricated and development of an improved de-embedding technique that takes parasitic impedances fully into account has enabled accurate extraction of the high frequency dielectric properties of the PbxSr1−xTiO3 films. Practically useful values of ε ∼ 1000, tan δ ∼ 0.03, and tunability ∼ 50% have been obtained in the low gigahertz range (1–5 GHz). Peaks in the dielectric loss due to acoustic resonance have been modeled and tentatively identified as due to an electrostrictive effect with an electromechanical coupling coefficient of ∼ 0.04 at an electric field of 240 kV/cm which is potentially useful for tunable thin film bulk acoustic wave devices.
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    Integration of sol-gel frequency agile materials for tunable RF devices
    (Cranfield University, 2012-01) Fragkiadakis, Charalampos; Kirby, Paul B.
    This thesis focuses on the use of high permittivity tunable dielectrics and more specifically sol-gel ferroelectric thin films for low cost, high performance tunable devices such as varactors and filters at RF and microwave frequencies. The topics covered include measurement techniques for the characterization of tunable dielectrics at low and microwave frequencies, fabrication processes, electrical and acoustic modeling of thin film ferroelectric varactors, performance optimization using conductive electrodes, realization of tunable microwave circuits and integration of tunable dielectrics with conventional bulk acoustic wave resonators (FBAR). Cont/d.