Ba1-xSrxTiO3 Based Thin Films for Next Generation Devices

Report No. ARL-TN-228
Authors: Eric Ngo, William D. Nothwang, Clifford Hubbard, Samuel Hirsch, Melanie W. Cole, Wontae Chang, Steven W. Kirchoffer, and Jeff M. Pond
Date/Pages: September 2004; 14 pages
Abstract: Over the past several years, there has been a tremendous growth and development of thin film deposition technology in the electronics industry. Ferroelectric thin films have been recognized for their unique dielectric properties and appear to be desirable for tunable microwave device applications. Among the most promising candidates for such applications are Ba1-xSrxTiO3(BST) and BST-based thin films. In this work, pure BST and acceptor doped BST-based thin films were fabricated on (100) MgO substrates via pulsed laser deposition. X-ray diffraction, in conjunction with the atomic force microscope, was used to analyze the film crystallinity and surface morphology. The dielectric properties were characterized at both 100 kHz and 20 GHz. The metal-insulator-metal capacitor configuration was used to attain the dielectric properties at 100 kHz, and the microwave measurements, S11 reflection parameters, were achieved via interdigitated capacitor design with Au/Ag top electrodes. The parallel resistor-capacitor models were used to determine the microwave capacitance and Q factors, and the permittivity was calculated using a modified conformal-mapping partial-capacitance method using the dimension of the capacitors. Our results demonstrated that the low frequency and microwave frequency dielectric properties were strongly influenced by the film composition. Specifically, the Mg doping served to lower the dissipation factor, permittivity, and tunability of the BST based films at both frequencies. This work demonstrates that the BST based thin films possessed excellent microstructural, structural, and dielectric properties. The structure-process-property correlations of the pulsed laser deposited BST and acceptor doped BST-based thin films are discussed in detail.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2004