Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N
Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N
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DOI：
10.1103/physrevmaterials.2.063802
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发表时间：
2018-06-29
影响因子：
3.4
通讯作者：
Brennecka, Geoff L.
中科院分区：
文献类型：
--
作者：
Talley, Kevin R.;Millican, Samantha L.;Brennecka, Geoff L.
了解氮化铝-氮化钪系统 (Al1-xScxN) 中合金化的异质结构影响可以突出通过利用非平衡态来增强所需材料性能的机会和设计原则。尽管最近由于对增强压电性能的兴趣而做出了巨大的努力，但该系统中基本的热力学以及成分和结构相关的机制以及潜在的性能演变尚未得到充分描述。然而，这些增强性能的实际实现受到系统中相分离的强大热力学驱动力的阻碍，这突出表明需要加强研究异质结构合金对该系统中热力学和成分-结构-性能关系的作用。考虑到这一需求，将从头计算合金热力学和性能与组合薄膜合成和表征进行比较，以更完整地了解 Al1-xScxN 成分空间的结构和性能演变。结构挫败和平坦的自由能景观相结合导致机电响应大幅增加。研究发现合金亚稳定性的能级比之前报道的要大得多，这有助于解释实现高钪浓度的均质材料的困难。钪替代铝软化了纤锌矿晶格，并且与竞争的六方氮化硼结构的能量接近增强了压电应力系数。总体而言，这项工作提供了对 Al1-xScxN 系统中结构-加工-性能关系的理解，提出了进一步增强性能的材料设计策略，并展示了非平衡异质结构合金增强的性能可调性和尚未充分探索的性质。
An understanding of the heterostructural implications on alloying in the aluminum nitride-scandium nitride system (Al1-xScxN) can highlight opportunities and design principles for enhancing desired material properties by leveraging nonequilibrium states. The fundamental thermodynamics, and therefore composition-and structure-dependent mechanisms, underlying property evolution in this system have not been fully described, despite significant recent efforts driven by interest in enhanced piezoelectric performance. Practical realization of these enhanced properties, however, is hindered by the strong driving thermodynamic driving force for phase separation in the system, highlighting the need for increased study into the role of heterostructural alloying on the thermodynamics and composition-structure-property relationships in this system. With this need in mind, ab initio computed alloy thermodynamics and properties are compared to combinatorial thin-film synthesis and characterization to develop a more complete picture of the structure and property evolution across the Al1-xScxN composition space. The combination of structural frustration and a flattened free-energy landscape lead to substantial increases in electromechanical response. The energy scale of alloy metastability is found to be much larger than previously reported, helping to explain difficulties in achieving homogeneous materials with high scandium concentration. Scandium substitution for aluminum softens the wurtzite crystal lattice, and energetic proximity to the competing hexagonal boron-nitride structure enhances the piezoelectric stress coefficient. Overall, this work provides insight into the understanding of the structure-processing-property relationships in the Al1-xScxN system, suggests material design strategies for even greater property enhancements, and demonstrates the increased property tunability and underexplored nature of nonequilibrium heterostructural alloys.