Defect Mediated Thin Film Growth

0090079SieradzkiNew方法用于在高温下电沉积原子平面异质外延层，其质量与超高真空技术相似。这项资助涉及的一个重要问题是这些新电沉积技术的普遍性。研究了许多异质外延金属/金属和金属/半导体系统，以解决与衬底取向和电解质组成有关的问题。采用敏感的原位应力监测技术研究生长过程中的应力松弛。利用应力演化的原位测量数据，可以确定重要的热力学参数，例如表征上覆层/衬底系统的界面应力。使用一种特殊的高速（每秒25张图像，图像尺寸为300 x 300像素）扫描隧道显微镜（STM）来研究允许缺陷和表面活性剂介导生长的原子尺度动力学过程的细节。理论工作使用动力学蒙特卡罗（KMC）技术，结合弹性相互作用来模拟生长和缺陷表面活性剂介导的生长。谐波模型和原子模型的结果以及实验动力学结果（高速STM）被整合到KMC模型中。在金属/金属吸附过程中，弹性相互作用在确定上层结构演化中的作用进行了研究。利用蒙特卡罗技术从实验吸附等温线中精确地提取了上层结构中附着原子的横向相互作用能。这些结果与上层结构的弹性模型进行了比较，以确定实验确定的横向相互作用能量的大小是否与弹性相互作用一致。这项工作可能会导致电沉积的新方法，产生类似于在高温下通过超高真空技术获得的质量的原子平面异质外延层。在一种方法中，感兴趣的金属与可逆沉积的中介金属共沉积。介质周期性地从表面沉积和剥离，每个循环产生新的核，导致一层一层地生长。在另一种方法中，使用浮在沉积金属表面的单层表面活性剂的规定分数。表面活性剂促进沉积金属的层间平台交换，从而最大限度地减少层内吸附原子扩散。这有助于显著增加层的成核密度，导致二维平面生长

0090079SieradzkiNew approaches are employed to electrodeposit atomically flat heteroepitaxial overlayers of quality similar to that obtained by ultra high vacuum techniques at elevated temperature. An important issue covered in this grant is the generality of these new electrodeposition techniques. A number of heteroepitaxial metal/metal and metal/semiconductor systems are examined to address issues related to substrate orientation and electrolyte composition. A sensitive in situ stress monitoring technique is employed to study stress relaxation during growth. Using data from in situ measurements of stress evolution, important thermodynamic parameters are determined such as interface stresses that characterize overlayer/substrate systems. A special high speed (25 images per second with image sizes of at 300 x 300 pixels) scanning tunneling microscope (STM) is used to investigate details of the atomic scale kinetic processes that allow defect and surfactant mediate growth to operate. Theoretical work uses Kinetic Monte Carlo (KMC) techniques that incorporate elastic interactions to model growth and the defect-surfactant mediated growth. The results obtained from harmonic and atomic models and experimental kinetic results (high speed STM) are integrated into the KMC modeling. The role of elastic interactions in determining the evolution of superstructures during metal/metal adsorption processes is examined. The lateral interaction energies of adatoms in superstructures are accurately extracted from experimental adsorption isotherms using Monte Carlo techniques. These results are compared to elastic models of superstructures in order to determine whether the experimentally determined magnitudes of lateral interaction energies are consistent with elastic interactions. %%%This work could lead to new approaches of electrodeposition that produce atomically flat heteroepitaxial overlayers of quality similar to that obtained by ultra high vacuum techniques at elevated temperature. In one approach the metal of interest is co-deposited with a reversibly deposited mediator metal. The mediator is periodically deposited and stripped from the surface and each cycle creates new nuclei leading to layer-by layer growth. In another approach, a prescribed fraction of a monolayer of surfactant is used that floats on the surface of the depositing metal. The surfactant promotes an interlayer terrace exchange of the depositing metal that minimizes intralayer adatom diffusion. This serves to significantly increase the nucleation density of the adlayer, leading to flat two-dimensional growth.***