Microstructures and dielectric properties of compositionally graded (Ba1-xSrx) TiO3 thin films prepared by pulsed laser deposition
Microstructures and dielectric properties of compositionally graded (Ba1-xSrx) TiO3 thin films prepared by pulsed laser deposition
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DOI：
10.1007/s003390201428
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发表时间：
2003-02
期刊：
影响因子：
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通讯作者：
X. Zhu;S. Lu;H. Chan;C. Choy;K. Wong
中科院分区：
文献类型：
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作者：
X. Zhu;S. Lu;H. Chan;C. Choy;K. Wong
采用逐层脉冲激光沉积法在Pt（111）/TiO 2/SiO2/Si（100）衬底上生长了（Ba 1-xSrx）TiO 3（BST）（x：0.0 ~ 0.25）组分梯度薄膜。制备了降级（Ba/Sr比从底表面的100/0变化到顶表面的75/25）和升级（Ba/Sr比从底表面的75/25变化到顶表面的100/0）BST膜。利用X射线衍射仪和扫描电子显微镜对它们的微观结构进行了系统的研究。随着沉积温度从550 °C升高到650 °C，在降级的BST薄膜中观察到了从大的“粗糙”（>0.30 μm）到小的致密晶粒（70-110 nm）的晶粒形态转变。没有这样的晶粒形态的转变中检测到的升级BST薄膜。用金属电极的介电测量揭示了降级膜的增强的介电行为。这种增强主要归因于降级膜与衬底之间的界面附近建立的大的压应力场。此外，在降级BST薄膜中的BaTiO 3层不仅作为底层，而且作为一个良好的种子层，用于增强在降级薄膜中的后续膜层的结晶。
Compositionally graded (Ba1-xSrx)TiO3(BST) (x:0.0∼0.25) thin films were grown on Pt (111)/TiO2/SiO2/Si (100) substrates using layer-by-layer pulsed laser deposition in the temperature range 550–650 °C. Both downgraded (Ba/Sr ratio varying from 100/0 at the bottom surface to 75/25 at the top surface) and upgraded (Ba/Sr ratio varying from 75/25 at the bottom surface to 100/0 at the top surface) BST films were prepared. Their microstructures were systematically studied by X-ray diffractometry and scanning electron microscopy. A grain morphology transition from large ‘rosettes’ (>0.30 μm) to small compact grains (70–110 nm) was observed in the downgraded BST films as the deposition temperature was increased from 550 to 650 °C. No such grain morphology transition was detected in the upgraded BST films. Dielectric measurements with metal electrodes revealed an enhanced dielectric behavior in the downgraded films. This enhancement is mainly attributed to the large compressive stress field built up near the interface between the downgraded film and substrate. Furthermore, the BaTiO3layer in the downgraded BST films not only serves as a bottom layer but also as an excellent seeding layer for enhancing the crystallization of the subsequent film layers in the downgraded films.