Growth of Ultra Thin Metal Alloy Films

这个研究项目研究了在非晶衬底上超薄（小于9纳米）非晶金属薄膜的生长。将研究化学生长方法，包括化学气相沉积和等离子体增强化学气相沉积。在第一性原理计算的指导下，本研究将研究合金元素，如磷、硼、硅和锡在稳定钌、钴、镍和钯薄膜中非晶微观结构方面的作用。目标是在最低合金浓度下形成非晶结构，从而保持金属性能。研究将集中在化学和物理方法来增加成核密度或改变膜组装过程，以实现2-4纳米厚的连续膜。实验还将探索选择性表面钝化剂，以阻止生长中的金属的反应，并在衬底上施加额外的成核。研究的目的是了解使反应和过程，这将导致最薄的连续薄膜，并具有非晶特性的超薄薄膜。工作计划将涉及薄膜生长和表征研究，并将涉及表面研究，以阐明当配体和底物被修饰时前体如何与底物相互作用。这项研究利用了德克萨斯大学的专业知识和实验基础设施来生长和表征薄膜，并研究表面反应。在衬底表面和薄膜界面的键合和反应将被探索。利用x射线光电子能谱、二次离子质谱和低能离子散射能谱跟踪薄膜的组成和化学键。完整的表征设备将用于研究薄膜，包括光谱椭偏仪、原子力显微镜、x射线散射光谱和高分辨率电子显微镜。知识优势：金属薄膜在传感器、光学和微电子领域有广泛的应用，随着应用和系统的关键尺寸或尺寸的减小，金属薄膜的厚度也必须减小到最多几十个原子直径，并且必须具有特定的微观结构。本课程旨在描述薄膜是如何形成的，重点是成核和岛状聚结，将薄膜与衬底结合的界面层的演变，块状材料的特性如何随厚度而变化，以及当薄膜厚度接近Veronoi多面体特征尺寸的5- 15倍时，短时秩序是如何保持的。这项研究的主要动机是非晶基板上的超薄金属薄膜在电极、传感器、光学、热障和扩散障等应用中的核心作用。该计划旨在探索超薄非晶金属形成和稳定中的短程有序的作用和性质。此外，本课程旨在描述影响薄膜演变的界面和表面反应，因为它从有核的岛屿转变为粘合的连续薄膜。成核和生长的问题是共同的非晶和多晶薄膜。该研究将直接支持研究生的培养，并间接为本科生参与开放式研究项目提供机会。PI和研究生将开发一个展览，帮助解释推动这项研究的革命性和当前设备，传感器和微电子，并向公众和大学预科学生介绍这些概念。他们将在德州大学赞助的各种场所展示它，比如一年一度的德州大学开放日和德州纪念博物馆。

0854345EkerdtThis research program investigates the growth of ultra thin (less than 9 nm) amorphous metal films on amorphous substrates. Chemical growth methods will be studied that include chemical vapor deposition and plasma-enhanced chemical vapor deposition. Guided by first-principles calculations, this research will examine the role of alloying elements, such as phosphorus, boron, silicon and tin on stabilizing an amorphous microstructure in ruthenium, cobalt, nickel and palladium films. The goal is to force an amorphous structure at the minimum alloy concentration so that the metal properties are retained. The research will focus on chemical and physical methods to increase the nucleation density or to alter the course of film assembly to realize continuous films that are 2-4 nm thick. Changes will be made to increase the defect density of the substrates and experiments will also explore selective surface passivants to block reaction on the growing metal and force additional nucleation on the substrate. The research objectives are an understanding of the enabling reactions and processes that will lead to the thinnest possible continuous film, and to an ultra thin film with amorphous character. The program of work will involve film growth and characterization studies and it will involve surface studies to elucidate how the precursors interact with the substrates as the ligands and substrates are modified. The research leverages the expertise and experimental infrastructure at the University of Texas to grow and characterize films and to study surface reactions. Bonding and reactions at the substrate surface and at the film interface will be explored. Film composition and chemical bonding will be followed using X-ray photoelectron spectroscopy, secondary ion mass spectrometry and low energy ion scattering spectroscopy. A full complement of characterization facilities will be used to study the films, including spectral ellipsometry, atomic force microscopy, X-ray scattering spectroscopy, and high resolution electron microscopy.Intellectual Merit: Metal films find applications in sensors, optics and microelectronics, and as the critical dimensions or size of the applications and systems decrease, the metal films thickness also must decrease to tens of atomic diameters at most and must have a specific microstructure. This program seeks to describe how films form, with an emphasis on nucleation and island coalescence, the evolution of interfacial layers that bind the film to the substrate, how properties of bulk materials scale with thickness, and precisely how short range order is preserved as the film thickness approaches thicknesses that are 5- 15 times the characteristic dimension of the Veronoi polyhedra.Broader Impacts of the Proposed Research This research is motivated in general by the central role ultra thin metal films on amorphous substrates have in applications such as electrodes, sensors, optics, thermal barriers, and diffusion barriers. This program seeks to explore the role and nature of short-range-order in the formation and stabilization of ultra thin amorphous metals. Further this program addresses and seeks to describe the interfacial and surface reactions that affect the evolution of the films as it transforms from nucleated islands to a coalesced, continuous film. Issues of nucleation and growth are common to both amorphous and polycrystalline films.The research will directly support the training of graduate students and indirectly provide opportunities for undergraduates to participate in open-ended research projects. The PI and the graduate student will develop an exhibit that will help explain the revolutionary and current devices that motivate this research, sensors and microelectronics, and introduce these concepts to the general public and to precollege students. They will present it and display it through a variety of University of Texas sponsored venues, such as the annual UT Open House and the Texas Memorial Museum.