npj:HfO2铁电体—掺杂剂间超大相互作用稳定了纳米相
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来自德国慕尼黑应用科学大学的Max Falkowski、Alfred Kersch和他们的同事对HfO2使用La或/和Si进行掺杂,其超结构具有1纳米的尺寸,他们对这些结构进行了高通量DFT计算,并将其与生产过程相联系。用粗粒度方法比较了在局部不均匀性的影响下,相关铁电Pbc21相的总能与竞争的晶体相总能进行了比较。他们发现掺杂剂之间的相互作用范围在1nm范围内,这与铁电相相对于介电相的稳定性有关。由于掺杂剂的相互作用,计算出的各结构相之间的能量变化出乎意料地大。掺杂剂之间的相互作用增加了掺杂剂随机定位的统计效应。在原子层或化学溶液沉积后的退火过程中,由于掺杂剂不会扩散,与陶瓷工艺回火相比,原子层或化学溶液沉积后的退火过程相对较短,但仍然存在较大的能量变化。由于能量差异是相稳定性的判据,这种大的变化表明存在纳米区和弥散相变的可能性,因为这些局部掺杂效应可能使系统在顺电-铁电相界上来回移动。这些结果对于理解新近的实验发现非常重要,例如居里温度变宽、相间边界和弥散相变等。
该文近期发表于npj Computational Materials 4: 73 (2018),英文标题与摘要如下,点击左下角“阅读原文”可以自由获取论文PDF。
Unexpectedly large energy variations from dopant interactions in ferroelectric HfO2from high-throughput ab initio calculations
Max Falkowski, Christopher Künneth, Robin Materlik & Alfred Kersch
Insight into the origin of process-related propertieslike small-scale inhomogeneities is key for material optimization. Here, weanalyze DFT calculations of randomly doped HfO2 structures withSi, La, and VO and relate them to the kind of productionprocess. Total energies of the relevant ferroelectric Pbc21 phaseare compared with the competing crystallographic phases under the influence ofthe arising local inhomogeneities in a coarse-grained approach. The interactionamong dopants adds to the statistical effect from the random positioning of thedopants. In anneals after atomic layer or chemical solution depositionprocesses, which are short compared to ceramic process tempering, the largeenergy variations remain because the dopants do not diffuse. Since the energydifference is the criterion for the phase stability, the large variationsuggests the possibility of nanoregions and diffuse phase transitions becausethese local doping effects may move the system over the paraelectric-ferroelectricphase boundary.
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