Browsing by Author "Huang, LC"

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Electrical properties of Mg/La, Mg/Nb co-doped (Ba0.7Sr0.3)TiO3 thin films prepared by metallo-organic deposition method
(2001-08-01)
Chen, SY
;
Wang, HW
;
Huang, LC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
(Ba0.7Sr0.3)TiO3 (BST) thin films doped with La, Nb and Mg ions along with an Mg/La, Mg/Nb codopant were prepared on Pt/Ti/SiO2/Si substrates by the metal-organic deposition method. A decrease of grain size, dielectric constant, and leakage current with increasing doping levels was observed for all studied cases. The grain size, dielectric constant and leakage current increased with increasing annealing temperatures for specimens doped with a single dopant. However, the leakage current was reduced to a minimum for the codoped materials at the donor/acceptor compensated concentration and decreased with increasing annealing temperatures. The decreased leakage current of the codoped materials could be explained by the additional barrier height and width of the insulating layer caused by the defect dipoles around grain boundaries.
Role of an intermediate phase (Ba,Sr)(2)Ti2O5CO3 in doped (Ba0.7Sr0.3)TiO3 thin films
(2003-01-30)
Chen, SY
;
Wang, HW
;
Huang, LC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
(Ba0.7Sr0.3)TiO3 (BST) thin films doped with La, Nb, and Mg ions were prepared by metal-organic deposition method (MOD) on Pt/Ti/SiO2/Si substrates. An intermediate phase formed under an annealing temperature of 550-650 degreesC, and disappeared at higher temperatures during the formation of BST. The intermediate phase was analyzed by X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), Fourier transform-infrared spectroscopy (FT-IR) and Raman spectra and found to be an oxycarbonate with a chemical formula of (Ba,Sr)(2)TiO5CO3. The stability of this intermediate phase increased with the addition of dopants, irrespective of doping types. It is proposed that distortion of crystal structure, physical constraint in the two-dimensions and small grain size favor the existence of poor crystallized (Ba,Sr)(2)Ti2O5CO3. (C) 2002 Elsevier Science B.V. All rights reserved.