溶膠凝膠法製備鈦酸鍶鋇多層薄膜的微觀結構與介電性質

Abstract

以溶膠凝膠法在Pt/Ti/SiO2/Si(100)基板上製備四種不同的Ba(1-X)SrXTiO3多層薄膜，並於500~800℃之間進行熱處理。以XRD、SEM、TEM及HRTEM等儀器分析多層薄膜的微觀結構，並且利用半導體參數分析儀量測介電性質及漏電流密度。當Sr含量增加，則Ba(1-X)SrXTiO3結晶溫度會下降，平均晶粒也會增大，這個現象可歸因於Sr2+離子半徑較Ba2+小，以致有較快的晶粒成長速率。添加甲醯胺使得Ba0.5Sr0.5TiO3結晶相溫度明顯下降，而且Ba0.9Sr0.1TiO3的中間相結晶量增多，而此Ba(1-X)SrXTiO3中間相計量比為Ba2-2xSr2xTi2O5CO3。在HRTEM觀察薄膜，亦發現其中有Ba2-2xSr2xTi2O5CO3中間相的結晶存在。電性量測的結果顯示，添加甲醯胺的Ba0.9Sr0.1TiO3/Ba0.5Sr0.5TiO3多層堆疊薄膜經650℃/1hr熱處理後，介電常數可達323，漏電流密度為1.26×10-6A/cm2。Ba0.5Sr0.5TiO3./ Ba0.9Sr0.1TiO3則有較低的介電常數(219)以及較大的漏電流密度(5.21×10-6A/cm2)。

Ba1-xSrxTiO3 (BST) multiplayer thin films were spin-coated on Pt/Ti/SiO2/Si(100) substrates by the sol gel method and heat-treated in air at temperatures ranging from 500 to 800oC. The microstructure of the multilayer thin films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The dielectric constants and the leakage current densities were measured using a semiconductor parameter analyzer. The addition of strontium to the BaTiO3 lattice increased the grain size of the crystallized films. The fact that grain size increased with the constant of strontium may be attributed to the higher growth rate due to the more rapid diffusion of the Sr2+ ion, which has a smaller ionic radius than Ba2+. Effects of formamide additives on powder and film properties were also investigated. HRTEM investigations show that the gel films crystallize as an intermediate carbonate phase, Ba2-2xSr2xTi2O5CO3. A dielectric constants of 323 and leakage current density of 5.21×10-6A/cm2 were measured for the Ba0.9Sr0.1TiO3/Ba0.5Sr0.5TiO3 multilayered thin films with the formamide additive after annealing 650℃ for 1hr and the dielectric constant (219) of various stacking Ba0.5Sr0.5TiO3/Ba0.9Sr0.1TiO3 multilayered thin films were smaller than that of Ba0.9Sr0.1TiO3/Ba0.5Sr0.5TiO3 and leakage current density (5.21x 10-6 A/cm2 ) were larger.