H Mŏk H Linh, Martínez-Aguilar E, Gervacio-Arciniega J J, Vendrell X, Siqueiros-Beltrones J M, Raymond-Herrera O
Posgrado en Física de Materiales, Centro de Investigación Científica y de Educación Superior de Ensenada, Carretera Tijuana-Ensenada No. 3918, Ensenada, Baja California, 22860, Mexico.
Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México AP 14, Ensenada, Baja California, 22860, Mexico.
Sci Rep. 2017 Dec 18;7(1):17721. doi: 10.1038/s41598-017-17767-3.
This work demonstrates that the rf-sputtering technique, combined with appropriate heat treatments, is potentially effective to develop new materials and devices based on oxide-interface and strain engineering. We report a study of the structural-physical properties relationship of high crystalline quality, highly oriented and epitaxial thin films of the lead-free (KNa)LaNbO (KNNLa) compound which were successfully deposited on Nb-doped SrTiO substrates, with orientations [100] (NSTO100) and [110] (NSTO110). The crystalline growth and the local ferroelectric and piezoelectric properties were evaluated by piezoresponse force microscopy combined with transmission electron microscopy and texture analysis by X-ray diffraction. Conditioned by the STO surface parameters, in the KNNLa films on NSTO100 coexist a commensurate [001]-tetragonal phase and two incommensurate [010]-monoclinic phases; while on NSTO110 the KNNLa films grew only in an incommensurate [101]-monoclinic phase. Both samples show excellent out-of-plane polarization switching patterns consistent with 180° domains walls; while for KNNLa/NSTO100 ferroelectric domains grow with the polarization pointing down, for KNNLa/NSTO110 they prefer to grow with the polarization pointing up. Comparing with previous reports on epitaxial KNN films, we find our samples to be of very high quality regarding their crystalline growth with highly ordered ferroelectric domains arrangements and, consequently, great potential for domain engineering.
这项工作表明，射频溅射技术与适当的热处理相结合，对于基于氧化物界面和应变工程开发新材料和器件具有潜在的有效性。我们报告了一项关于无铅（KNa）LaNbO（KNNLa）化合物的高质量结晶、高度取向和外延薄膜的结构-物理性能关系的研究，这些薄膜成功地沉积在掺铌的SrTiO衬底上，取向为[100]（NSTO100）和[110]（NSTO110）。通过压电力显微镜结合透射电子显微镜以及X射线衍射纹理分析来评估晶体生长以及局部铁电和压电性能。受STO表面参数的影响，在NSTO100上的KNNLa薄膜中，[001]四方相和两个非共格[010]单斜相共存；而在NSTO110上，KNNLa薄膜仅以非共格[101]单斜相生长。两个样品都显示出与180°畴壁一致的出色的面外极化切换模式；对于KNNLa/NSTO100，铁电畴以极化方向向下生长，而对于KNNLa/NSTO110，它们倾向于以极化方向向上生长。与之前关于外延KNN薄膜的报道相比，我们发现我们的样品在晶体生长方面具有非常高的质量，具有高度有序的铁电畴排列，因此在畴工程方面具有巨大潜力。
