Preparation and Diclectric Properties of Ferroelectric BaTiO_3 Thin Films by Sol-Gel Method

BaTiO_3薄膜在多层电容器、铁电存储器、热释电探测器和电光器件等方面的应用已得到了广泛的研究。制备BaTiO_3薄膜的方法有溅射法、真空蒸发法、金属有机分解法和溶胶-凝胶法。近年来，采用活化反应蒸发、脉冲激光分解和溶胶-凝胶法等方法制备了具有P-E磁滞回线的BaTiO_3薄膜。然而，在Sol-Gel法制备的BaTiO_3薄膜的介电常数-温度特性曲线中，在120ﾟC附近没有观察到居里峰。为了制备具有较大颗粒的BaTiO_3薄膜，采用了高达850ﾟC的处理温度，这有利于铂片的使用。铂…上制备的BaTiO_3薄膜的结晶度、表面形貌和电学性能在850ﾟC温度下观察到更多的衬底，在铂衬底上制备的BaTiO_3薄膜具有微细的颗粒结构，颗粒尺寸约为50 nm。单层薄膜的微观结构为不均匀织构，大的孤立颗粒尺寸约为450 nm。随着镀膜/加热工艺循环次数的增加，大小为100 nm左右的细小颗粒似乎从粗大的孤立颗粒表面长大，最终通过多次镀膜/加热工艺制备的薄膜具有强烈的细晶织构。在铂衬底上制备的BaTiO_3薄膜的P-E磁滞回线显示出饱和的磁滞回线。制备的薄膜在室温下的Pr为3.8，电导率为20KV/cm。在室温下，铂衬底上的薄膜的介电常数约为830，介电常数约为0.04。在这些薄膜中，在约120ﾟC处没有观察到居里峰，而在70ﾟC左右观察到了较宽的居里峰。居里温度的差异可能是由于BaTiO_3尺寸和微结构的影响。较少

BaTiO_3 thin films have been intensively investigated for application to multilayr capacitors, ferroelectric memories, pyroelectric detectors and electrooptic devices. A number of techniques such as sputtering, vacuum evaporation, metalorganic decomposition and sol-gel methods have been used to prepare BaTiO_3 thin films. Recently, BaTiO_3 thin films that exhibit P-E hysteresis loops have been prepared by activated reactive evaporation, , pulsed laser decomposition and sol-gel methods. However, in the dielectric constant -temperaturecharacteristic curves of BaTiO_3 thim films prepared by sol-gel method, a curie peak was not observed at a temperature around 120ﾟC.In this work, BaTiO_3 thin films were prepared by sol-gel method. In order to prepare BaTiO_3 thin films with relatively large grains, the processing temperature as high as 850ﾟC was utilized, facilitating the use of Pt plate. Their crystallinity, surface morphology and electrical properties of BaTiO_3 thin films prepared on Pt … More substrate at 850ﾟC were examined.The BaTiO_3 thin films on Pt substrate exhibited a slightly coares grain microstructure with grain sizes of about 50nm. And, the microstructure of single-layr films showed inhomogeneous texture with large isolated grains of about 450nm. Increasing with the cycles of coating/heating process, fine grains as small as about 100nm seemed to grow from the surfaces of large isolated grains and, finally, thin films prepared by multiple coating/heating processes were strongly textured with fine grains. That is, the grain sizes of the top layr of the multilayr thin films were always much finer than those of the first coating.P-E hysteresis loops of BaTiO_3 thin films prepared on Pt indicated well-saturated hysteresis loops. And, these thin films prepared exhibited Pr of 3.8 and Ec of 20kV/cm at room temperature. The thin films on Pt substrate exhibited epsilonr of about 830 and tan delta of 0.04 at room temperature. And, inthese films, the curie peak was not seen at about 120ﾟC.However, broad curie peaks were observed at around 70ﾟC.The difference of the curie temperatures may be due to the effect of BaTiO_3 sizes and the microstructure. Less