Abstract

Transition metals implanted in a stable oxide can either precipitate out at grain boundaries or can remain embedded in bulk. For MgO, experimentally it has been observed that some of the implanted Fe atoms precipitate out, while few Fe atoms in 2+ and 3+ charge states remain embedded in the lattice. Using first-principles calculations based on density functional theory, we show that formation energy, dopant site, barrier of transition and diffusivity, all these factors collectively determine the chance of precipitation of the implanted ion in the host lattice. Our calculations revealed that at 600 K (typical annealing temperature) while neutral iron in MgO would migrate 1 \(\mu \)m in few microseconds, it takes several years for the charged Fe ions to migrate the same distance. On the other hand, Ni ions in all its charge states (neutral, 1+, 2+, and 3+) would migrate 1 \(\mu \)m in just few microseconds, at 600 K. While explaining the experimentally observed precipitation of implanted Ni and few Fe atoms in MgO, this work provides a new scheme for predicting the stability of an implanted ion against precipitation in any stable rock-salt structured oxide.

Graphic abstract

中文翻译：

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关于注入MgO的过渡金属沉淀的起源

摘要

植入稳定氧化物中的过渡金属可能会在晶界处沉淀出来，或者可能保持大量嵌入。对于MgO，实验观察到一些注入的Fe原子沉淀出来，而2+和3+电荷态的Fe原子仍保留在晶格中。使用基于密度泛函理论的第一性原理计算，我们表明形成能，掺杂位点，过渡势垒和扩散率，所有这些因素共同决定了注入离子在主体晶格中沉淀的机会。我们的计算表明，在600 K（典型退火温度）下，MgO中的中性铁会迁移1  \（\ mu \）在几微秒的毫秒数内，带电的Fe离子迁移相同的距离需要花费数年的时间。在另一方面，Ni离子在其所有的电荷状态（中性，1 +，2 +，和3+）将迁移1 \（\亩\）米只需几个微秒，在600 K.虽然说明实验观察到的沉淀由于在MgO中注入了Ni和少量Fe原子，这项工作为预测注入的离子对任何稳定的岩盐结构氧化物中的沉淀的稳定性提供了新方案。

图形摘要