We have studied the growth of epitaxial films of stannate pyrochlores with a general formula A₂Sn₂O₇ (A = La and Y) and find that it is possible to incorporate ∼25% excess of the A-site constituent; in contrast, any tin excess is expelled. We unravel the defect chemistry, allowing for the incorporation of excess A-site species and the mechanism behind the tin expulsion. An A-site surplus is manifested by a shift in the film diffraction peaks, and the expulsion of tin is apparent from the surface morphology of the film. In an attempt to increase La₂Sn₂O₇ conductivity through n-type doping, substantial quantities of tin have been substituted by antimony while maintaining good film quality. The sample remained insulating as explained by first-principles computations, showing that both the oxygen vacancy and antimony-on-tin substitutional defects are deep. Similar conclusions are drawn on Y₂Sn₂O₇. An alternative n-type dopant, fluorine on oxygen, is shallow according to computations and more likely to lead to electrical conductivity. The bandgaps of stoichiometric La₂Sn₂O₇ and Y₂Sn₂O₇ films were determined by spectroscopic ellipsometry to be 4.2 eV and 4.48 eV, respectively.

中文翻译：

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外延锡酸盐烧绿石薄膜：阳离子化学计量和电子掺杂的局限性

我们研究了通式为A ₂ Sn ₂ O ₇ ( A = La 和 Y)的锡酸盐烧绿石外延膜的生长，发现可以掺入约 25% 过量的A位成分；相反，任何多余的锡都会被排出。我们解开了缺陷化学，允许加入过量的A位物种和锡排出背后的机制。的甲-site过剩是通过在膜衍射峰的位移表现出来，和锡的排出是从膜的表面形态显而易见。为了增加 La ₂ Sn ₂ O ₇通过n型掺杂提高导电性，大量锡已被锑取代，同时保持良好的薄膜质量。正如第一性原理计算所解释的那样，样品保持绝缘，表明氧空位和锡上锑替代缺陷都很深。在Y ₂ Sn ₂ O ₇上得出了类似的结论。另一种n型掺杂剂，氧上的氟，根据计算是浅的，更可能导致导电性。化学计量的La ₂ Sn ₂ O ₇和Y ₂ Sn ₂ O ₇的带隙 通过光谱椭偏法测定的薄膜分别为 4.2 eV 和 4.48 eV。