Browsing by Author "Nayak, M"

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Dielectric tunability of barium strontium titanate films prepared by a sol-gel method
(2002-04-03)
Nayak, M
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The electric field tuning property of the 100-kHz dielectric constant of Ba0.5Sr0.5TiO3 (BST) thin films deposited on Pt/Ti/SiO2/Si substrates by a hydroxide-alkoxide-based sol-gel method was investigated by varying the annealing temperature, the thickness and the precursor solution concentration. The tunability and dielectric constant of the BST thin films increased with increasing annealing temperature, indicating the dependence of the tunability on parameters of the film quality, such as crystallinity and grain size. A similar to 235-nm film annealed at 700 degreesC showed tunability of approximately 48%. Variation of the precursor solution concentration resulted in a different microstructure, which in turn affected the tunability of the film. The dielectric tunability of the film showed a small increase as the film thickness increased in contrast, the figure of merit decreased because of the increase in dielectric loss. Experimental results showed that increases in dielectric constant and tunability are always associated with larger dielectric loss, which effectively decrease the figure of merit. (C) 2002 Elsevier Science B.V. All rights reserved.
Electrical and dielectric properties of (Ba0.5Sr0.5)TiO3 thin films prepared by a hydroxide-alkoxide precursor-based sol-gel method
(2003-01-02)
Nayak, M
;
Lee, SY
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Thin films of barium strontium titanate with composition (Ba0.5Sr0.5)TiO3 were prepared by a sol-gel method using Ba-, Sr-hydroxides, titanium(IV) isopropoxide as source materials and 2-methoxyethanol as the solvent. Well-crystallised films were obtained at relatively low temperatures. We observed grain growth accompanied with increase in the dielectric constant as the annealing temperature increased. The films prepared from this method and annealed at 800degreesC showed high dielectric constant of 650. Typical leakage current density of the film annealed at 700degreesC is 0.8 x 10(-6) at 75 W cm(-1). The change in electrical characteristics of the films has been correlated to their microstructure, which revealed that the concentration change affected the film porosity and grain size distribution. The results indicate that the microstructure could be tailored by changing the precursor solution concentration. (C) 2002 Elsevier Science B.V. All rights reserved.
Sol-gel derived (Ba0.5Sr0.5)TiO3 thin films and their electrical and dielectric properties
(2001)
Nayak, M
;
Lee, SY
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Barium strontium titanate thin films with composition (Ba0.5Sr0.5)TiO3 were prepared by a sot-gel method using hydroxide-alkoxide precursors. Reasonably well-crystallized film was obtained at a temperature as low as 500 degreesC. The leakage current characteristics and dielectric constant of the films varied with the annealing temperature due to the change in microstructure. The electrical and dielectric properties of the films showed strong dependence on the precursor solution concentration. Dielectric response of the films prepared from dilute solution is superior to that prepared from the concentrated solution. The change in electrical and dielectric characteristics of the films has been correlated to their microstructure, which revealed that the concentration change affected the grain size distribution, film porosity and morphology.