Defect Mediated Thin Film Growth

Sieradzki 0090079 Sieradzki 0090079采用新的方法来电沉积原子级平坦的异质外延覆盖层，其质量类似于在高温下通过超高真空技术获得的质量。 这项补助金所涵盖的一个重要问题是这些新电沉积技术的普遍性。许多异质外延金属/金属和金属/半导体系统进行检查，以解决有关基板取向和电解质组合物的问题。 采用灵敏的原地应力监测技术来研究生长过程中的应力松弛。 使用的数据，从现场测量的应力演化，重要的热力学参数确定，如界面应力的特点覆盖层/基板系统。一个特殊的高速（每秒25张图像，图像尺寸为300 x 300像素）扫描隧道显微镜（STM）被用来研究原子尺度的动力学过程的细节，允许缺陷和表面活性剂介导的生长操作。理论工作使用动力学蒙特卡罗（KMC）技术，将弹性相互作用模型的增长和缺陷表面活性剂介导的增长。从谐波和原子模型和实验动力学结果（高速STM）得到的结果集成到KMC建模。弹性相互作用的作用，在确定金属/金属吸附过程中的超结构的演变进行检查。利用Monte Carlo方法从实验吸附等温线中精确地提取了超结构中吸附原子的横向相互作用能。这些结果进行了比较，以确定是否实验确定的横向相互作用能量的大小与弹性相互作用的弹性模型。这项工作可能导致新的电沉积方法，产生原子级平坦的异质外延覆盖层的质量类似于超高真空技术在高温下获得的。 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。介体周期性地沉积并从表面剥离，并且每个循环产生新的核，导致逐层生长。在另一种方法中，使用漂浮在沉积金属表面上的表面活性剂单层的规定部分。表面活性剂促进沉积金属的层间平台交换，使层内吸附原子扩散最小化。这有助于显着增加吸附层的成核密度，从而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.***