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3 June 1998 Structure/property relationships in pulsed-laser-deposited ferroelectric thin films for frequency-agile microwave electronics
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Low loss ferroelectric thin films deposited by pulsed laser deposition (PLD) are currently being used to develop a new class of tunable microwave circuits based on the electric field dependence of the dielectric constant. Single phase, (100) oriented Ba0.5Sr0.5TiO3 (BST) films have been deposited onto (100) LaAlO3, SrTiO3, and MgO substrates. Interdigitated capacitors have been used to measure the dielectric constant and dissipation factor of these films as a function of DC bias and temperature at 1 MHz and as a function of DC bias at 1 to 20 GHz at room temperature. A low phase noise voltage controlled oscillator is currently being developed for use at frequencies from 1 - 20 GHz. To achieve low phase noise in the oscillator will require the loss tangent in the ferroelectric to be <EQ 5 X 10-3. Origins of the dielectric loss are being investigated using optical techniques. Optical imaging of the ferroelectric films using confocal scanning optical microscopy shows reproducible polarization fluctuations over sub-micrometer length scales for BST films deposited onto SrTiO3 which are not observed for films deposited onto MgO. Dielectric loss in the ferroelectric film is reduced through a combination of post deposition processing and donor/acceptor doping of the films. The lowest dielectric loss measured at microwave frequencies (tan(delta) equals 0.01 at 1 - 10 GHz) has been in a post-deposition annealed Ba0.5Sr0.5TiO3 film doped with approximately 1 - 2 atomic % Mn.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
James S. Horwitz, A. C. Carter, Wontae Chang, Jeffrey M. Pond, Steven W. Kirchoefer, Douglas B. Chrisey, J. Levy, and C. Hubert "Structure/property relationships in pulsed-laser-deposited ferroelectric thin films for frequency-agile microwave electronics", Proc. SPIE 3274, Laser Applications in Microelectronic and Optoelectronic Manufacturing III, (3 June 1998);

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