CAREER: Using Colloidal Suspensions to Investigate the Role of Particle Dynamics in Heteroepitaxy and Melting

* 技术摘要 * 外延在固态和有机半导体器件的制造、应变消除纳米结构阵列的创建以及具有新颖光学和机械性能的涂层的设计中起着关键作用。了解工作中各种生长过程的微观细节仍然是表面和材料科学研究的中心焦点。在最近的工作中，胶体悬浮液被用来表明，动态机制的基础上的扩散运动的颗粒之间的间隙网站的移动，大大有助于步骤的边缘和角落的障碍，确定岛的形态，并最终得到的结晶膜的光滑度。这些扩散机制提出了控制薄膜形态的新途径。为了在这个问题上取得进展，这个项目将结合胶体科学的技术来研究扩散布朗粒子动力学对异质外延和熔化的影响。特别是，这些扩散动力学在设置生长和熔化速率以及基板上的粒子间的相互作用是不相称的粒子的优选晶格间距所发挥的作用将被确定。最终，这些调查将提出新的路线控制薄膜形态在自组装和外延生长的晶体。由于这些工艺在纳米技术和半导体制造中无处不在，因此在这些调查中发现的发现有可能从根本上改变这些行业中使用的实践。该项目将支持博士生的教育，并开展一些外联活动，包括组织科学讲习班和为各弱势社区的K-12教师编写教材。* 非技术摘要 * 为什么有些材料生长出近乎完美的晶体，表面镜面光滑，而另一些材料生长出粗糙、凹凸不平的晶体？最近，人们直接观察到了晶体的真实的时间生长。不是通过观察单个原子，而是通过冻结可以用光学显微镜直接观察的模型原子。使用比人类头发小50倍的微小塑料球溶液，重现了导致原子尺度结晶的条件。除了简单地观察颗粒结晶之外，还表明颗粒的随机飞镖运动是决定颗粒如何容易地离开生长岛屿的关键因素。当粒子可以更容易地跳离岛时，光滑的晶体就生长出来了。该项目将建立在这些结果的基础上，并研究应变晶体表面上的结晶和熔化。将这些发现应用于原子尺度将能够更好地控制用于制造计算机和手机电子元件的薄膜的生长和熔化。该项目将支持博士生的教育，并开展一些外联活动，包括组织科学讲习班和为各弱势社区的K-12教师编写教材。

****Technical Abstract****Epitaxy plays a pivotal role in the fabrication of solid state and organic semiconductor devices, creation of strain relief nanostructured arrays, and design of coatings with novel optical and mechanical properties. Understanding the microscopic details of the various growth processes at work continues to be a central focus of surface and materials science research. In recent work colloidal suspensions were used to show that dynamic mechanisms based on the diffusive motion of particles moving between interstitial sites contribute substantially to the step edge and corner barriers that determine island morphology and ultimately the smoothness of the resulting crystalline film. These diffusive mechanisms suggest new routes towards controlling film morphology. To make progress on this question this project will integrate techniques in colloid science to investigate the effects that diffusive Brownian particle dynamics have on heteroepitaxy and melting. In particular, the role played by these diffusive dynamics in setting growth and melting rates as well as the interparticle interactions on substrates that are incommensurate with the prefered lattice spacings of the particles will be determined. Ultimately these investigations will suggest new routes for controlling thin film morphology during self assembly and epitaxial growth of crystals. Since these processes are ubiquitously used in nanotechnology and semiconductor fabrication, discoveries made during these investigations have the potential to fundamentally shift practices used in these industries. This project will support the education of PhD students as well as develop a number of outreach activities including the organization of scientific workshops and the development of educational materials for K-12 teachers in various disadvantaged communities. ****NON-TECNICAL ABSTRACT****Why do some materials grow near-perfect crystals with mirror-smooth faces whereas others grow rough, bumpy crystals? Recently, the real time growth crystals was directly observed? not by watching individual atoms, but rather by freezing model atoms that can be observed directly with an optical microscope. Using a solution of tiny plastic spheres 50 times smaller than a human hair, conditions that lead to crystallization on the atomic scale were reproduced. In addition to simply watching the particles crystallize it was shown that the random darting motion of a particle is a key factor that determines how easily particles can move off a growing island. When particles can hop off islands more easily, smooth crystals are grown. This project will build on these results and investigate both crystallization and melting on surfaces that strain the crystals. Application of these findings to the atomic scale will enable better control over the growth and melting of thin films used to manufacture electronic components for our computers and cell phones. This project will support the education of PhD students as well as develop a number of outreach activities including the organization of scientific workshops and the development of educational materials for K-12 teachers in various disadvantaged communities.