Vermolen E C M, Kuijk A, Filion L C, Hermes M, Thijssen J H J, Dijkstra M, van Blaaderen A
Soft Condensed Matter, Debye Institute for NanoMaterials Science, Utrecht University, Princetonplein 1, NL-3584 CC Utrecht, The Netherlands.
Proc Natl Acad Sci U S A. 2009 Sep 22;106(38):16063-7. doi: 10.1073/pnas.0900605106. Epub 2009 Sep 9.
Binary colloidal crystals offer great potential for tuning material properties for applications in, for example, photonics, semiconductors and spintronics, because they allow the positioning of particles with quite different characteristics on one lattice. For micrometer-sized colloids, it is believed that gravity and slow crystallization rates hinder the formation of high-quality binary crystals. Here, we present methods for growing binary colloidal crystals with a NaCl structure from relatively heavy, hard-sphere-like, micrometer-sized silica particles by exploring the following external fields: electric, gravitational, and dielectrophoretic fields and a structured surface (colloidal epitaxy). Our simulations show that the free-energy difference between the NaCl and NiAs structures, which differ in their stacking of the hexagonal planes of the larger spheres, is very small (approximately 0.002 k(B)T). However, we demonstrate that the fcc stacking of the large spheres, which is crucial for obtaining the pure NaCl structure, can be favored by using a combination of the above-mentioned external fields. In this way, we have successfully fabricated large, 3D, oriented single crystals having a NaCl structure without stacking disorder.
二元胶体晶体在调整材料特性以用于例如光子学、半导体和自旋电子学等应用方面具有巨大潜力，因为它们能够将具有截然不同特性的粒子定位在同一个晶格上。对于微米级胶体，人们认为重力和缓慢的结晶速率会阻碍高质量二元晶体的形成。在此，我们通过探索以下外部场：电场、引力场、介电泳场和结构化表面（胶体外延），展示了从相对较重的、类似硬球的微米级二氧化硅颗粒生长具有氯化钠结构的二元胶体晶体的方法。我们的模拟表明，氯化钠和砷化镍结构之间的自由能差非常小（约为0.002k(B)T），这两种结构在较大球体的六方平面堆叠方式上有所不同。然而，我们证明，通过使用上述外部场的组合，可以有利于大球体的面心立方堆叠，这对于获得纯氯化钠结构至关重要。通过这种方式，我们成功制备出了具有氯化钠结构且无堆叠无序的大型三维定向单晶。
