Experimental Studies of Surface Transport Aspects of Electrodeposition and Corrosion

摘要CTS-9527497 这项工作的目标是开发和应用一种方法来测量在固液界面的电极上的表面扩散。 该方法使用伏安法，微分电容，和表面二次谐波产生（SHG）。 研究的系统包括金上的铅（111）和银上的氯、铅或铜（111）。 邻位金（111）的实验使用纯粹的伏安测量来获得阶地和台阶上的相对覆盖率;这种分配对稀溶液沉积速率的依赖性给出了表面扩散的间接测量。 表面扩散的直接测量。 直接测量表面扩散银（111）使用表面SHG，吸附的非线性光学探针能够亚单层选择;这些实验有两种类型：测量的衰减的表面衍射光栅，和测量的衰减的一维浓度步骤。 第一种技术采用激光诱导热脱附（LITD）来创建衍射光栅，并使用SHG来监测其衰减速率，这是由表面扩散引起的。 第二种技术涉及通过LITD或通过掩蔽真空蒸发来创建阶跃浓度分布，其衰减由SHG监测。 一个玻尔兹曼-蒙塔诺分析的衰减给出了覆盖依赖的扩散率，需要描述宏观电沉积过程。 SHG信号经验相关的表面覆盖两种电化学方法：溶出伏安法和微分电容。 表面扩散是电沉积和电溶解的基本步骤之一，并且在某些工业情况下是限速的。 然而，这种现象很少被研究，因为它是实验无法达到的。 本研究的目的是纠正这一点，最终目标是将表面扩散和成核的微观信息到特征尺度（形态学）模拟亚半微米电沉积贵金属互连和电接触。 ***

ABSTRACT CTS-9527497 The goal of this effort is to develop and apply a methodology to measure surface diffusion on electrodes at the solid-liquid interface. The approach uses voltammetry, differential capacitance, and surface second harmonic generation (SHG). Systems studied include lead on gold (111) and chlorine, lead, or copper on silver (111). Experiments on vicinal gold (111) use a purely voltammetric measurement to obtain the relative coverage on terraces and steps; the dependence of this partitioning on the deposition rate from dilute solutions gives an indirect measure of surface diffusion. Direct measurements of surface diffusion. Direct measurements of surface diffusion on silver (111) use surface SHG, a nonlinear optical probe of adsorption capable of submonolayer selection; these experiments are two types: measurement of the decay of a surface diffraction grating, and measurement of the decay of a one-dimensional concentration step. The first technique employs laser-induced thermal desorption (LITD) to create a diffraction grating and uses SHG to monitor its rate of decay, which is caused by surface diffusion. The second techniques involves creation of a step concentration profile, either by LITD or by masked vacuum evaporation, the decay of which is monitored by SHG. A Boltzmann-Montano analysis of the decay gives the coverage-dependent diffusivity that is needed to describe macroscopic electrodeposition processes. The SHG signal is related empirically to surface coverage by two electrochemical methods: stripping voltammetry and differential capacitance. Surface diffusion is one of the fundamental steps in electrodeposition and electrodissolution, and is rate-limiting in some industrial situations. Nevertheless, the phenomenon is little studied because it is experimentally inaccessible. This study aims to rectify this with the eventual goal of incorporating microscopic information on surface diffusion and nucleation into feature-scale (morphological) simula tion of sub-half-micron electrodeposition of noble-metal interconnects and electrical contacts. ***