Defect Mediated Thin Film Growth

采用新的方法电沉积原子扁平的异质外延层，其质量类似于高温超高真空技术所获得的质量。这笔赠款涉及的一个重要问题是这些新的电沉积技术的一般性。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液组成有关的问题。采用一种灵敏的地应力监测技术来研究生长过程中的应力松弛。利用现场测量的应力演化数据，确定了重要的热力学参数，如表征覆盖层/衬底系统的界面应力。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)被用来研究允许缺陷和表面活性剂中介生长的原子尺度动力学过程的细节。理论工作使用了动力学蒙特卡罗(KMC)技术，该技术结合了弹性相互作用来模拟生长和缺陷-表面活性剂介导的生长。从谐和原子模型得到的结果和实验动力学结果(高速扫描隧道显微镜)被整合到KMC模型中。研究了弹性相互作用在金属/金属吸附过程中决定超结构演化的作用。用蒙特卡罗方法从实验吸附等温线中准确地提取了超结构中吸附原子的横向相互作用能。将这些结果与上层建筑的弹性模型进行比较，以确定实验确定的横向相互作用能大小是否与弹性相互作用一致。%这项工作可能导致新的电沉积方法，以产生质量类似于高温超高真空技术获得的原子平坦的异质外延覆盖层。在一种方法中，感兴趣的金属与可逆沉积的介体金属共沉积。介体被周期性地沉积并从表面剥离，每个循环都会产生新的原子核，导致逐层生长。在另一种方法中，使用规定比例的单层表面活性剂，它漂浮在沉积金属的表面上。表面活性剂促进了沉积金属的层间阶梯交换，最小化了层内吸附原子的扩散。这有助于显著增加附着层的成核密度，导致平坦的二维生长。

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.***