Nucleation and Growth of Thin Films and Nanostructures

薄膜和纳米结构的成核和生长

• 批准号: 1160195
• 负责人: John Ekerdt
• 金额: $ 30.54万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-06-01 至 2016-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1160195&HistoricalAwards=false
• 关键词: Nucleation; Growth; Thin; Films; Nanostructures

This research program investigates the nucleation and growth of metal nanoparticles and ultra thin metal films on amorphous substrates. Chemical growth methods will be studied that include chemical vapor deposition and atomic layer deposition. The research will focus on measuring the concentration and elucidating the chemical nature of defect sites on amorphous substrates were nucleation is initiated or where stable metal clusters are trapped. The program will probe the chemical nature of inherent defects and defects that are purposefully generated on the substrates. Fluorescent probe molecules designed to chemically titrate different proposed defect sites will be used to measure the concentration of the defects and possibly also their spatial distribution. The way the different defects affect nucleation and metal adatom trapping will be established. The research will also explore approaches to inhibit/block the growth of established metal islands and force a higher nucleation density as a route to smooth and ultra thin continuous films. The program will involve ruthenium, cobalt and tungsten metals, and silicon dioxide, aluminum oxide, and titanium dioxide as the supports. The overall objectives are to understand and describe the surface chemistry that allows metal nucleation to occur, and to determine if it is possible to control the growth of particles to maximize the nucleation density on the oxide substrate. 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 and low energy ion scattering spectroscopy. A full complement of characterization facilities will be used to study the films, including fluorimetry, 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. Nanoparticles are used in advanced computer memory design, catalysis and quantum computing architectures; in all cases, there is a need to maximize the particle density and uniformity. This research is expected to develop a general understanding of how metal films and metal nanoparticles nucleate on amorphous oxide surfaces and initiate island growth. Nucleation and growth concepts are common to nanoparticles and polycrystalline films. The nucleation and growth issues explored transcend the material systems selected for this project.Broader Impacts: This research is motivated by the central role ultra thin metal films and nanoparticles on amorphous substrates have in applications such as electrodes, sensors, optics, thermal barriers, catalysts and diffusion barriers. There is an extensive literature pointing to the possible role of defects in nucleation and growth, however, there are few studies on amorphous surfaces that have measured and characterized the nature of these defects. This program seeks to use chemical probes designed to titrate the different defects. The fluorescence signal intensity suggest a sensitivity to 0.001 and possibly 0.0001 monolayers with these probes. If successful, the probes could be used to explore oxides more generally. Further this program addresses and seeks to describe the interfacial and surface reactions that affect the evolution of a film as it transforms from adsorbed adatoms to nucleated islands to a coalesced, continuous film.

该研究项目研究非晶基底上金属纳米颗粒和超薄金属薄膜的成核和生长。将研究化学生长方法，包括化学气相沉积和原子层沉积。该研究将侧重于测量非晶基底上缺陷位点的浓度并阐明其化学性质，这些缺陷位点是引发成核或稳定金属簇被捕获的地方。该计划将探测固有缺陷和在基材上有意产生的缺陷的化学性质。设计用于化学滴定不同的缺陷位点的荧光探针分子将用于测量缺陷的浓度以及它们的空间分布。将建立不同缺陷影响成核和金属吸附原子捕获的方式。该研究还将探索抑制/阻止已形成的金属岛生长并迫使更高的成核密度的方法，作为平滑和超薄连续薄膜的途径。该项目将涉及钌、钴和钨金属，以及二氧化硅、氧化铝和二氧化钛作为载体。总体目标是了解和描述允许金属成核发生的表面化学，并确定是否可以控制颗粒的生长以最大化氧化物基材上的成核密度。将探索基底表面和薄膜界面处的键合和反应。将使用 X 射线光电子能谱和低能离子散射谱来跟踪薄膜成分和化学键合。将使用全套表征设施来研究薄膜，包括荧光测定法、原子力显微镜、X射线散射光谱和高分辨率电子显微镜。 智力优点：金属薄膜在传感器、光学和微电子领域得到应用，随着应用和系统的临界尺寸或尺寸减小，金属薄膜的厚度也必须减小到数十个原子直径 最多并且必须具有特定的微观结构。纳米粒子用于先进的计算机内存设计、催化和量子计算架构；在所有情况下，都需要最大化颗粒密度和均匀性。这项研究有望对金属薄膜和金属纳米粒子如何在非晶氧化物表面成核并引发岛生长有一个总体的了解。成核和生长概念对于纳米粒子和多晶薄膜来说是常见的。探索的成核和生长问题超越了该项目所选的材料系统。更广泛的影响：这项研究的动机是非晶基底上的超薄金属薄膜和纳米颗粒在电极、传感器、光学、热障、催化剂和扩散障壁等应用中的核心作用。有大量文献指出缺陷在成核和生长中可能发挥的作用，然而，对非晶表面测量和表征这些缺陷性质的研究却很少。该计划旨在使用化学探针来滴定不同的缺陷。荧光信号强度表明这些探针对 0.001 甚至可能 0.0001 单层的灵敏度。如果成功，这些探针可用于更广泛地探索氧化物。此外，该程序还致力于并试图描述影响薄膜从吸附的吸附原子到有核岛再到聚结的连续薄膜转变过程中的界面和表面反应。