Relation of Gas Phase Species to Film Growth by Pulsed Laser Deposition

古德温9529309 在过去的五年中，相当大的努力一直致力于诊断分析的物质羽流时，脉冲激光器被用来烧蚀固体目标。 这主要是出于更好地理解脉冲激光沉积重要的基本物理和化学过程的需要，脉冲激光沉积是一种新流行的薄膜生长技术，其在超导体、绝缘体和半导体结构的生长中的应用越来越多。 目的是从激光诱导羽流，而不是专门研究羽流的形成。 所采取的方法是实验和理论相结合的努力。 简而言之，目的是确定膜化学计量和微观结构由以下因素决定的程度： 当羽流接近用于薄膜生长的衬底时，气相物质的能量分布（平移和内部）的演变。 入射物质的能量将影响粘附概率、解离概率以及解离和掺入的模式（即，吸附或注入）气相成分到膜中。 随着羽流从靶向衬底移动，物种分布的演变，包括在气相中形成活性中间体，然后冷凝到固体表面上。 实验工作的突出方面是气相羽流的激光诱导荧光（LIF）测量，在其电子基态的中间物种，在原位表面分析反射高能电子衍射（RHEED）和一个互补的核心水平的光谱技术在加州理工学院，反射电子能量损失光谱（REELS）。 各种形式的后生长膜微观结构分析将被用来分析膜的化学计量，密度，结晶度，键合状态和光学性能。 理论工作将涉及几个方面的努力，包括高能羽流表面相互作用离子的分子动力学（MD）模拟和气相羽流动力学（包括化学动力学和衬底相互作用）的直接模拟蒙特卡罗（DSMC）模拟。 ***

Goodwin 9529309 In the last five years, considerable effort has been devoted to diagnostic analysis of the plumes of matter produced when pulsed lasers are used to ablate a solid target. this has been primarily motivated by a desire to better understand the basic physical and chemical processes important to pulsed laser deposition, a newly popular thin film growth technique which is finding ever-increasing application to growth of superconductor, insulator and semiconductor structures. The objective from laser-induced plumes, rather than to study exclusively plume formation. The approach taken is a combined experimental and theoretical effort. Briefly, the aim is to determine the extent to which film stoichiometry and microstructure are determined by: Evolution of the energy distributions (both translational and internal) of the gas phase species as the plume approaches a substrate for thin film growth. The incident species' energy will affect the sticking probability, the dissociate probability and mode of dissociation and incorporation (i.e., adsorption or implantation) of gas phase constituents into the films. Evolution of species distributions as the plume moves from the target to the substrate, including formation of reactive intermediates in the gas phase, which then condense onto the solid surface. Prominent aspects of the experimental work are laser-induced fluorescence (LIF) measurements of gas phase plume an intermediate species in their electronic ground states, in situ surface analysis by reflection high energy electron diffraction (RHEED) and a complementary core level spectroscopy technique developed at Caltech, reflection electron energy loss spectroscopy (REELS). Various forms of postgrowth film microstructural analysis will be used to analyze film stoichiometry, density, crystallinity, bonding state, and optical properties. The theoretical work will involve several efforts, including molecular dynamics (MD) simulations of energetic plume-surface interact ions and Director-Simulation Monte Carlo (DSMC) simulations of gas-phase plume dynamics, including chemical kinetics and substrate interactions. ***