Effects of Excess Bi Concentration, Buffered Bi2O3 Layer, and Ta Doping on the Orientation and Ferroelectricity of Chemical-Solution-Deposited Bi3.25La0.75Ti3 O12 Films
Authors: Lin, Jian-Long; Chang, Tian-Lin; Lin, Wen-Tai
Source: Journal of Electronic Materials, Volume 33, Number 10, 1 October 2004 , pp. 1248-1252(5)
Abstract:Effects of excess Bi concentration, buffered Bi2O3 layer, and Ta doping on the orientation and ferroelectricity of chemical-solution-deposited (CSD) Bi3.25La0.75Ti3O12 (BLT) films on Pt/SiO2/Si(100) were studied. The optimum concentration of excess Bi added to the BLT films to achieve a larger remanent polarization (2Pr) was 10 mol.%. The buffered Bi2O3 layers could reduce the temperature for c-axis-oriented growth of BLT films from 850°C to 700°C. However, two-step annealing, i.e., first annealed at 650°C and then annealed at a temperature of 700–850°C, could effectively suppress the c-axis-oriented growth and thus improve the 2Pr of BLT films. The improvement of the 2Pr of BLT films can be explained in terms of the large polarization along the a-axis orientation and buffered Bi2O3 layers, which compensate the BLT films for Bi evaporation during annealing. The Ta doping can induce two contrary effects on the 2Pr of BLT films. For the (Bi3.25La0.75)(Ti3–xTax)O12 (BLTTx) films with x = 0.005, the effect of a decrease of oxygen vacancies would be dominant, resulting in the improvement of 2Pr. Because the Ta concentration (x) in the BLTTx films exceeds 0.01, the effect of a decrease of grain size would become dominant, resulting in the degradation of 2Pr.
Document Type: Regular Paper
Publication date: 2004-10-01