The blocking effect of surface dislocations on oxygen tracer diffusion in SrTiO3.
The blocking effect of surface dislocations on oxygen tracer diffusion in SrTiO3.
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DOI：
10.1039/c8cp02191k
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发表时间：
2018-06
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影响因子：
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通讯作者：
H. Schraknepper;T. Weirich;R. D. De Souza
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文献类型：
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作者：
H. Schraknepper;T. Weirich;R. D. De Souza
在扩散研究中，为了研究氧空位和位错之间的相互作用，在标准的，名义上未掺杂的，单晶SrTiO 3的表面处存在的抛光引起的损伤区。这种晶体的示踪剂扩散配置文件提出了表现出三个功能：一个短的功能所产生的表面空间电荷层;一个中间，较长的功能所产生的高密度的位错在受损区;最后，一个更长的功能对应于扩散的均匀的大块晶体。定量信息由有限元法计算提供。首先，在样品中的氧空位的分布，其中空间电荷区耗尽的氧空位形成在位错和样品表面的计算，随后，氧示踪剂的扩散分布，这样的空位分布进行了模拟。通过对商业单晶SrTiO 3进行常规氧同位素交换和深度剖析实验，对所提出的模型进行了实验验证。通过这种方式，我们直接证实，在受主掺杂的SrTiO 3中的位错阵列，凭借伴随的空间电荷管，阻碍了氧的扩散。最后，为了帮助抛光钙钛矿单晶衬底中的氧示踪剂扩散分布的预测，我们建议一个一维的连续的方法，考虑到复杂的，三维的扩散问题所造成的位错阵列与耗尽空间电荷管。
The existence of a polishing-induced damaged zone at the surface of standard, nominally undoped, single-crystal SrTiO3 is exploited in diffusion studies in order to investigate the interaction between oxygen vacancies and dislocations. Tracer diffusion profiles for such crystals are proposed to exhibit three features: a short feature arising from a surface space-charge layer; an intermediate, longer feature arising from the high density of dislocations in the damaged zone; and finally, a much longer feature corresponding to diffusion in the homogeneous bulk crystal. Quantitative information is provided by finite-element-method calculations. First, the distribution of oxygen vacancies in a sample in which space-charge zones depleted of oxygen vacancies form at dislocations and at the sample surface is calculated; subsequently, oxygen tracer diffusion profiles for such vacancy distributions are simulated. The proposed model is experimentally validated by performing conventional oxygen isotope exchange and depth-profiling experiments on commercial single-crystal SrTiO3. In this way, we confirm directly that arrays of dislocations in acceptor-doped SrTiO3, by virtue of the attendant space-charge tubes, hinder the diffusion of oxygen. Finally, in order to aid the prediction of oxygen tracer diffusion profiles in polished perovskite single-crystal substrates, we suggest a one-dimensional continuum approach that takes account of the complex, three-dimensional diffusion problem posed by dislocation arrays with depletion space-charge tubes.