Browsing by Author "Lee, VC"

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Aging behavior and recovery of polarization in Sr0.8Bi2.4Ta2O9 thin films
(2000-03-15)
Chen, SY
;
Lee, VC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Ferroelectric thin films of bismuth-containing layered perovskite Sr0.8Bi2.4Ta2O9 (SBT) have been prepared by both metalorganic decomposition (designated as MOD-SBT film) and magnetron sputtering (designated as sputtering-SBT film) processes. SBT thin films are well known to exhibit free-fatigue behavior with electrical field cycling. However, it was found that after the SBT films were applied with electrical field display, the polarization reduction with time was observed. The aging rate was related to microstructure, which in turn was dependent on the film processing. The sputtering-SBT films show a slower degradation rate than MOD-SBT films. The suppressed polarization can be near-completely recovered by applying either thermal treatment above 150 degrees C or electric-field cycling. There exists a minimum required thermal energy to restore the polarization. The easy recovery exhibited by SBT films in suppressed polarization reveals that a relatively weak domain pinning may exist between domain wall and electronic defects in SBT. The SBT shows little fatigue behavior during electric field cycling but exhibits an aging phenomenon after applied electric field. (C) 2000 American Institute of Physics. [S0021-8979(00)04906-9].
Effect of lead additive on the ferroelectric properties and microstructure of SrxPbyBi2zTa2O9 thin films
(2000-06-01)
Chen, SY
;
Lee, VC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Ferroelectric thin films of bismuth-containing layered perovskite SrxPbyBi2zTa2O9 have been prepared using the metalorganic decomposition method. The effect of both Sr and Pb content on the crystal structure, microstructure, and ferroelectric properties of SrxPbyBi2.3Ta2O9 films was investigated. A maximum remanent polarization of 2P(r)=19.2 mu C/cm(2) was obtained for the SrxPb0.2Bi2.3Ta2O9 film with 20 mol % Sr-deficient composition as prepared at 800 degrees C, which could be the compromising effects of Sr content on both grain growth and second phase formation of BiTaO4. The substitution of Pb for Bi is accompanied by the occurrence of oxygen vacancies to compensate the charge balance, which is responsible for grain growth mechanism in Sr0.8Pb0.2Bi2.3Ta2O9 films. Fatigue endurance of Sr0.8Bi2.3Ta2O9 films becomes problematic after 10(9) cycles with a decrease in remanent polarization to 85% of the original value. This phenomenon was related to electron injection and creation of electron traps due to the occupation of Sr vacancies by Bi cations. It is demonstrated that the fatigue endurance of Sr0.8Bi2.3Ta2O9 film can be improved by doping with 20 mol % PbO. (C) 2000 American Institute of Physics. [S0021- 8979(00)01311-6].