PECASE: Mechanisms of Surfactant Mediated Thin Film Growth

摘要CTS-9733416 Eric I.阿尔特曼/耶鲁大学 微电子学、光电子学和磁记录技术都依赖于生长低缺陷密度、连续、超薄薄膜的能力。本项目的目的是确定如何通过添加表面活性剂来促进超薄连续膜的生长。 表面活性剂对成核和生长动力学和机制的影响将使用原位变温扫描隧道显微镜（STM）进行研究。所观察到的机制和动力学将用于开发表面活性剂介导的生长的动力学蒙特卡罗模拟。 模拟将被用来调查的增长模式的不同的动力学参数的敏感性，从而将揭示成功地使用表面活性剂形成稳定的，超薄连续膜所需的关键功能。 对于几乎所有的应用，Frank-van der Merwe（F-vdM）或逐层生长是优选的生长模式，因为它产生可能的最薄、最均匀、连续的膜。 当基底的表面张力大于膜的界面张力和表面张力之和时，有利于Frank-van der Merwe生长。即使当F-vdM生长是有利的，动力学限制可能导致新层的成核之前，先前的层完成。 添加表面活性剂可以通过改变表面和界面张力以及成核和生长动力学来促进F-vdM生长。 最近的研究表明，后者是更重要的，虽然在表面活性剂的存在下的成核和生长机制和动力学仍然在很大程度上是一个猜测的问题。 因此，我们将研究的关键基本过程，支配表面活性剂介导的成核和生长的动力学：表面扩散，扩散跨越步骤，附着步骤，adatom表面活性剂交换障碍，成核。 比较两个非常不同的系统，Ag和Ge在Si（100）上的生长与V族表面活性剂，将揭示成功地使用表面活性剂来促进F-vdM生长所需的关键特征，以及膜、衬底和表面活性剂之间的相互作用的性质如何影响动力学参数。 在微电子、光电子和磁记录等广泛应用中的持续进步取决于在工业标准Si（100）衬底上形成超薄、低缺陷密度膜的能力。具体地，在Si（100）上生长光滑Ge膜的方法的开发被视为开发基于Ge-Si合金和超晶格结构的高速集成电路的关键，并且Ag-Si系统作为薄膜磁性结构的基础而受到关注。

ABSTRACT CTS-9733416 Eric I. Altman/Yale U. Microelectronics, optoelectronics, and magnetic recording technologies all rely on the ability to grow low defect density, continuous, ultra-thin films. The objective of this project is to determine how the growth of ultra-thin continuous films can be promoted by addition of surfactants. The effect of surfactants on nucleation and growth kinetics and mechanisms will be studied using in situ variable-temperature scanning tunneling microscopy (STM). The observed mechanisms and kinetics will be used to develop kinetic Monte Carlo simulations of surfactant mediated growth. The simulations will be used to investigate the sensitivity of the growth mode to the different kinetic parameters and thus will reveal the key features required to successfully use surfactants to form stable, ultra-thin continuous films. For almost all applications Frank-van der Merwe (F-vdM) or layer-by-layer growth is the preferred growth mode because it results in the thinnest, most uniform, continuous films possible. Frank-van der Merwe growth is favored when the surface tension of the substrate is greater than the sum of the interfacial tension and the surface tension of the film. Even when F-vdM growth is favored, kinetic limitations can lead to nucleation of new layers before the previous layers are completed. Addition of a surfactant can promote F-vdM growth by altering both surface and interfacial tensions and nucleation and growth kinetics. Recent studies suggest the latter is more important, although nucleation and growth mechanisms and kinetics in the presence of a surfactant remain largely a matter of speculation. Therefore, we will investigate the kinetics of the key elementary processes that govern surfactant mediated nucleation and growth: surface diffusion, diffusion across steps, attachment to steps, adatom-surfactant exchange barrier, nucleation. Comparison of two very different systems, Ag and Ge growth on Si(100) with group V surfactants, will reve al the key features required to successfully use surfactants to promote F-vdM growth, and how the kinetic parameters are affected by the nature of the interactions between the film, the substrate and the surfactant. Continued advances in a wide range of applications including microelectronics, optoelectronics and magnetic recording depend on the ability to form ultra-thin, low-defect density films on industry standard Si(100) substrates. Specifically, the development of methods to grow smooth Ge films on Si(100) is seen as a key to developing high-speed integrated circuits based on Ge-Si alloy and superlattice structures, and the Ag-Si system is of interest as a base for thin film magnetic structures.