Growth of CeO_2 thin films deposited on biaxially textured nickel substrates
Growth of CeO_2 thin films deposited on biaxially textured nickel substrates
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双轴织构镍基底上沉积 CeO_2 薄膜的生长
DOI：
10.1557/jmr.2003.0004
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发表时间：
2003
影响因子：
2.7
通讯作者：
W. Prusseit
中科院分区：
文献类型：
--
作者：
D. Eyidi;M. Croitoru;O. Eibl;R. Nemetschek;W. Prusseit
CeO_2薄膜是在{100}-双向织构的Ni衬底上制备YBa2Cu3O7超导−δ薄膜的缓冲层，得到了Ni-CeO2-YBa2Cu3O7−δ层序列。Ni-CeO_2界面为金属-氧化物界面，衬底与薄膜的失配度约为9%。文献中提出了该体系的外延生长模型。所研究的薄膜是在衬底温度650-670°C，沉积后厚度为100 nm的条件下用反应热蒸发法沉积的。用平面法和剖面法、原子力显微镜和扫描电子显微镜对CeO2薄膜进行了表征。CeO2薄膜具有较强的{100}双轴织构，粗糙度约为90 nm。电子显微镜观察表明，在Ni-CeO2界面上没有发现中间层。薄膜为柱状晶，直径为20~50 nm，远小于Ni基片的晶粒度，大于1μm，晶界呈小角度，且有少量的<111>取向。应用了莫尔条纹技术，该技术非常适合于成像CeO2小颗粒相对于镍衬底的小旋转(≤3°)。这些小颗粒的小旋转表明，生长是非外延的，但却是双向织构的。在CeO2薄膜样品中，观察到尺寸为5-10 nm的纳米空洞，且大多位于薄膜表面附近。在此基础上提出了在镍衬底上生长CeO_2薄膜的模型。
CeO_2 films are technologically important as buffer layers for the integration of superconducting YBa_2Cu_3O_7−δ films on {100}-biaxially textured Ni substrates, yielding a Ni–CeO_2–YBa_2Cu_3O_7−δ layer sequence. The Ni–CeO_2 interface is a metal–oxide interface, and the misfit between substrate and film is about 9%. An epitaxial growth model was suggested for this system in the literature. The investigated films were deposited by a reactive thermal evaporation process at substrate temperatures of 650–670 °C with a thickness of 100 nm after deposition. The CeO_2 films were characterized by plan-view and cross-section transmission electron microscopy, atomic force microscopy, and scanning electron microscopy. The CeO_2 films had a strong {100} biaxial texture with a roughness of approximately 90 nm. No intermediate layer could be found by cross-section transmission electron microscopy at the Ni–CeO_2 interface. The films had columnar grains with diameters of 20–50 nm, much smaller than the grain size of the Ni substrate, which was larger than 1 μm. Small-angle grain boundaries and small amounts of 〈111〉-oriented grains were evidenced in plan-view samples by diffraction patterns. The Moiré fringes technique was applied and was ideally suited to image the small rotations (≤3°) of the small CeO_2 grains with respect to the Ni substrate. These small rotations of small grains showed that the growth was nonepitaxial, however, biaxially textured. In the CeO_2 film samples, nanovoids 5–10 nm in size were observed and were mostly located close to the film surface. A model for the growth of CeO_2 thin films on nickel substrates can be proposed on the basis of our results.