Browsing by Author "Lan, BC"

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Effect of titanium substitution on film structure and ferroelectric properties of Sr-deficient Sr0.75Bi2.35Ta2O9 thin films
(2002-12-20)
Chen, SY
;
Lan, BC
;
Taso, CS
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Ferroelectric films of bismuth-containing layered perovskite Sr0.75Bi2.35(Ta2-x,Ti-x)O-9 (x=0-0.8) have been prepared using a metal organic decomposition method. The effects of Ti substitution on the rnicrostructure evolution and ferroelectric properties of Sr0.75Bi2.35Ta2O9 films were investigated. A maximum remanent polarization of 2P(r)=30.7 muC/cm(2) was obtained for the Sr0.75Bi2.35Ta1.8Ti0.2O9 film as compared to Sr0.75Bi2.35Ta2O9 films (19.6 muC/cm(2)) annealed at 800 degreesC in air. The Ti substitution for Ta leads to charge compensation for the self-produced positive Bi-Sr(.), due to the occupation of Bi on Sr vacancies and is responsible for the increase in leakage resistance. The leakage current density as low as 2 X 10(-8) A/cm(2) can be obtained at an applied electric field of 100 kV/cm. Substitution of Ti for Ta shows a positive effect on the fatigue endurance of Sr-deficient Sr0.75Bi2.35Ta2O9 film. (C) 2002 Elsevier Science B.V. All rights reserved.
Film structure and ferroelectric properties of vanadium-doped Sr0.8Bi2.3Ta2O9 thin films
(2002-06-15)
Chen, SY
;
Lan, BC
;
Taso, CS
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Vanadium-doped strontium bismuth tantalate Sr0.8Bi2.3(Ta2-xVx)O-9 (SBTV) (x = 0-0.8) have been prepared on Pt/Ti/SiO2/Si substrates using a metalorganic decomposition method. Well-crystallized and dense SBTV films can be obtained at an annealing temperature as lower as 650-700 degreesC that can be attributed to the enhanced densification due to the addition of vanadium. With partial substitution of tantalum by vanadium up to x = 0.15, a larger remanent polarization (2P(r)) of 30.5 muC/cm(2) can be obtained for the Sr0.8Bi2.3Ta1.85V0.15O9 film at 800 degreesC that is attributed to the larger grain size and increased "rattling space." Furthermore, the vanadium substitution for tantalum ion can effectively reduce the leakage current density as lower as 5 x 10(-8) A/cm(2) at an applied electric field of 100 kV/cm because of the reduced mobility of charge carriers. However, the incorporation of vanadium does not cause appreciable negative effect on the fatigue endurance of Sr-deficient Sr0.8Bi2.3Ta2O9 films until more than 20 mol % (x = 0.2) vanadium was added. (C) 2002 American Institute of Physics.
Forming gas annealing on physical characteristics and electrical properties of Sr0.8Bi2Ta2O9/Al2O3/Si capacitors
(2003-08-01)
Lan, BC
;
Hsu, JJ
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Chen, SY
;
Bow, JS
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材料科學與工程學系
Sr0.8Bi2Ta2O9 (SBT) ferroelectric film constructed on Al2O3/Si to form metal-ferroelectric-insulator-semiconductor (MFIS) was prepared to study the degradation behavior of SBT films under forming gas annealing (FGA). Although the diffusion of hydrogen ions has been detected during FGA treatment, no significant differences in the microstructure and crystalline phase are observed for the SBT film compared to that without FGA treatment. However, the diffusion of hydrogen ions leads to the rapid decrease in the dielectric constant but shows no apparent influence on the memory window of Sr0.8Bi2Ta2O9/Al2O3/Si capacitors. In addition, it was found that FGA shows a positive effect on the leakage current of MFIS in contrast to that of metal/ferroelectric/metal structure. The leakage current density of MFIS dramatically decreases as much as two orders of magnitude after FGA at 500degreesC compared to that without FGA treatment that was attributed to the reduced defects at the interface of Al2O3/Si. (C) 2003 American Institute of Physics.
Physical characteristics and electrical properties of Sr0.8Bi2+xTa2O9 films on Al2O3/Si annealed at high temperature
(2003-11-15)
Lan, BC
;
Huang, CY
;
Chen, SY
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Bismuth-containing layered perovskite Sr0.8Bi2+xTa2O9 (SBT) thin films with x=0-0.8 were prepared to investigate annealing temperature effect, especially at high temperature, on physical characteristics and electrical properties of SBT films on Al2O3 (10 nm)/Si. At 800 degreesC, the Sr0.8Bi2Ta2+xO9/Al2O3/Si exhibits ferroelectric mode and the width of memory window decreases with the increase of Bi content that is dependent on the effective coercive field. However, at a higher annealing temperature of 900 degreesC, a larger ferroelectric memory window was obtained for Bi-rich Sr0.8Bi2+xTa2O9 (x=0.4 or 0.8) films compared to SBT film (x=0) that should be related to the reduced leakage current due to the formation of rod-shape grains and amorphous SBT composite layer. The leakage current of Sr0.8Bi2.4Ta2O9/Al2O3/Si annealed at 900 degreesC is about 1.2x10(-9) A/cm(2) that has two orders of magnitude lower than that of 800 degreesC-annealed SBT films measured at -100 kV/cm. However, the Sr0.8Bi2Ta2O9 (x=0) film on Al2O3/Si capacitor shows no obvious change with the increase of annealing temperature. (C) 2003 American Institute of Physics.
Stability and formation of pyrochlore phase in doped Sr0.8Bi2.3Ta2O9 thin films
(2003-06-01)
Chen, SY
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Lan, BC
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Taso, CS
;
Lee, SY
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材料科學與工程學系
Ferroelectric thin films of bismuth-containing layered perovskite Sr0.8Bi2.3Ta2-xMxO9 (SBTM), where M is V, Ti, W, and Zr. hake been prepared on Pt/Ti/SiO2/Si substrates using the metal-organic decomposition method. The effect of the incorporated B-site cations on pyrochlore phase formation and microstructure evolution of SBTM films was investigated. The pyrochlore phase formation has been identified due to out-diffusion of titanium from underneath platinum layer to participate in the reaction with the films. Furthermore, the formation of pyrochlore phase in the SBTM films has been observed strongly dependent on the characteristics of incorporated M cation. The substitution of both W and V for Ta leads to the formation of pyrochlore phase at lower annealing temperature (750-800 degreesC). On the other hand, the addition of Zr can retard the formation of pyrochlore phase from 850 to 900 degreesC. A model based on the binding energy of octahedral structure is used to elucidate the formation and stability of the pyrochlore phase present in the SBT film. (C) 2003 Elsevier Science B.V. All rights reserved.
Temperature dependent integrity of Sr0.8Bi2Ta2O9 films on ultra-thin Al2O3 buffered Si
(2003-04-29)
Lan, BC
;
Chen, SY
;
Lee, HY
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The annealing temperature dependent integrity of Sr0.8Bi2Ta2O9 (SBT) on ultra-thin 4 nm SiO2 and Al2O3 buffered Si was investigated in this work. Although the capacitance-voltage characteristics show hysteresis loops in both cases, the memory window of Sr0.8Bi2Ta2O9/Al2O3 capacitor is larger than that of Sr0.8Bi2Ta2O9/SiO2 capacitor. As increasing annealing temperature from 800 to 900degreesC, the grain size and memory window of polycrystalline SBT increase both cases. At 800degreesC, the leakage current density of Sr0.8Bi2Ta2O9/Al2O3 capacitor is 3.2 x 10(-8) A/cm(2) at -3V, which is low enough for deep sub-mum application. With increasing temperature to 900degreesC, the leakage current in both structures becomes smaller. (C) 2002 Elsevier Science B.V. All rights reserved.