Crystallinity Dependence of Microwave Dielectric Properties in (Ba,Sr)TiO3 Thin Films

概要

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The dielectric properties of (Ba0.43Sr0.57)TiO3 (BST) thin films were investigated in the microwave-frequency range. The dielectric losses ($\tan\delta$) and dielectric constants ($\varepsilon$) were successfully measured up to ${\sim}6$ GHz using a circular-patch capacitor geometry. The deposition temperatures were varied from room temperature to 750°C to investigate the effects of crystallinity on the dielectric properties. As the film crystallinity was enhanced, the dielectric losses increased from $0.0024\pm 0.0018$ at room-temperature to $0.0102\pm 0.0017$ at 750°C deposition. The dielectric constants varied from $10.29\pm 0.02$ to $243\pm 1$ in the same deposition-temperature range. Raman spectroscopy showed that the increase in dielectric losses of the BST thin films was correlated with the growth of microscopic polar regions induced by symmetry-breaking defects. Because the sizes of these regions are proportional to the dielectric constants of host lattices (crystallinity), dielectric losses increase with the deposition temperatures.
INSTITUTE OF PURE AND APPLIED PHYSICSの論文
2003-03-15