Department of Chemistry, University of Oregon, Eugene, OR, 97403, USA.
Department of Materials Science and Engineering, University of Florida, Gainesville, FL, USA.
Angew Chem Int Ed Engl. 2017 Nov 13;56(46):14448-14452. doi: 10.1002/anie.201707270. Epub 2017 Oct 2.
The discovery of emergent phenomena in 2D materials has sparked substantial research efforts in the materials community. A significant experimental challenge for this field is exerting atomistic control over the structure and composition of the constituent 2D layers and understanding how the interactions between layers drive both structure and properties. While no segregation for single bilayers was observed, segregation of Pb to the surface of three bilayer thick PbSe-SnSe alloy layers was discovered within [(Pb Sn Se) ] (TiSe ) heterostructures using electron microscopy. This segregation is thermodynamically favored to occur when Pb Sn Se layers are interdigitated with TiSe monolayers. DFT calculations indicate that the observed segregation depends on what is adjacent to the Pb Sn Se layers. The interplay between interface- and volume-free energies controls both the structure and composition of the constituent layers, which can be tuned using layer thickness.
二维材料中涌现现象的发现激发了材料科学界的大量研究工作。该领域的一个重大实验挑战是对组成二维层的结构和成分进行原子级控制，并了解层间相互作用如何驱动结构和性质。虽然没有观察到单层的分离，但在(PbSnSe) 异质结构中，发现了 Pb 在三层厚的 PbSe-SnSe 合金层表面的分离。当 PbSnSe 层与 TiSe 单层交错时，这种分离在热力学上是有利的。DFT 计算表明，观察到的分离取决于与 PbSnSe 层相邻的物质。界面和体自由能之间的相互作用控制了组成层的结构和组成，可以通过层厚进行调节。
