Chemical Vapor Deposition of Si-containing Thin Films and Si Nanostructures: From a molecular-level understanding to applications

热线化学气相沉积（HWCVD）的技术涉及源气体的催化解离以在加热的金属线上形成自由基，以及随后的气相中的自由基-自由基和自由基-分子反应以产生与衬底反应的膜生长前体，导致薄膜形成。这些气相生长前体强烈影响沉积膜的生长速率和性质。为了找到最终产品的最佳和所需性能的黄金配方，工业界做出了大量努力，最常见的是通过试错法。我们采用了一种独特的方法，试图了解使用HWCVD形成薄膜的化学和物理过程。为此，在技术上要求苛刻的激光电离质谱（LIMS）技术将采用作为强大的诊断工具，以确定气相薄膜生长的前体，并研究化学动力学的氮化硅（SiNx）和碳氮化物（SiCyNz）薄膜的HWCVD过程中，这些前体物种的生产与不同的源气体系统。这项工作的基础化学将有助于开发新的，环境友好的前体和合理的改进方法，以找到最好的配方在HWCVD的SiNx/SiCyNz薄膜的工业应用在光电子和微电子。我们的目标还在于使用强大的LIMS诊断工具，对CVD生长Si纳米线（SiNWs）中Si原子形成的化学反应有一个基本的了解。这可能有助于填补目前SiNW CVD生长模型中的一些空白。在硅纳米线的广泛应用中，我们专注于它们作为锂离子电池（LIB）负极材料的用途。Si是最有前途的锂离子电池负极材料之一，因为它的理论充电容量最高。为了解决使用Si作为LIB阳极的关键挑战，即由于插入和提取Li时的大体积膨胀而导致的容量衰减，我们提出通过使用有组织的金属纳米颗粒阵列（MNAs）作为CVD生长中的催化剂来制造具有预定义间距和尺寸的有序SiNW阵列。通过脉冲激光诱导去湿（PLiD）的新技术，将完成可控形成的MNAs的预图案化的基板上的金属薄膜的电化学方法制备。开发的协议可以提供一种替代方法，以昂贵的光刻为基础的方法。最后，开发的PLiD方法将探索形成的Pt为基础的CuMnAs作为燃料电池反应的电催化剂，以限制昂贵的Pt的量，并获得新的催化剂具有增强的选择性，活性和稳定性。总体而言，拟议的研究将推进我们目前的知识的两个CVD工艺- HWCVD的SiNx/SiCyNz薄膜和CVD生长的SiNW。这也将有助于锂离子电池阳极材料和燃料电池催化剂的发展。

The technique of hot wire chemical vapor deposition (HWCVD) involves catalytic dissociation of source gases to form radicals on a heated metal wire and subsequent radical-radical and radical-molecule reactions in the gas phase to produce film growth precursors that react with the substrate, leading to thin film formation. These gas-phase growth precursors strongly affect the growth rate and properties of the deposited films. A lot of industrial efforts have been made to find the golden recipe for optimal and desired properties of final products, most often by trial-and-error methods. We have adopted a unique approach trying to understand the chemical and physical processes underpinning the thin film formation using HWCVD. For this, the technically demanding laser ionization mass spectrometric (LIMS) techniques will be employed as powerful diagnostic tools to identify the gas-phase film growth precursors and to study the chemical kinetics governing the production of these precursor species in the HWCVD processes of silicon nitride (SiNx) and carbonitride (SiCyNz) thin films with different source gas systems. This work on the underlying chemistry will help develop novel, environmentally benign precursors and rational improvement methods to find the best recipe in HWCVD of SiNx/SiCyNz films for industrial applications in optoelectronics and microelectronics. We also aim at a fundamental understanding of the chemical reactions responsible for the formation of Si atoms in the CVD growth of Si nanowires (SiNWs) using the powerful LIMS diagnostic tools. This could help fill in some gaps in the current CVD growth models for SiNWs. Among a wide spectrum of applications of SiNWs, we focus on their use as anode materials in lithium ion batteries (LIB). Si is one of the most promising LIB anode materials due to its highest known theoretical charge capacity. To tackle the key challenge in using Si as LIB anode, which is the capacity fading due to the large volume expansion upon insertion and extraction of Li, we propose to fabricate an ordered array of SiNWs with pre-defined spacing and size by using organized metal nanoparticle arrays (MNAs) as catalysts in the CVD growth. The controlled formation of MNAs will be accomplished by the novel technique of pulsed laser-induced dewetting (PLiD) of metal films on pre-patterned substrates prepared by electrochemical methods. The developed protocol could provide an alternative method to the expensive lithography-based methods. Finally, the developed PLiD methods will be explored for the formation of Pt-based bimetallic MNAs as electrocatalysts for fuel cell reactions to limit the amount of expensive Pt and to obtain new catalysts with enhanced selectivity, activity and stability. Overall, the proposed research will advance our current knowledge of the two CVD processes - HWCVD of SiNx/SiCyNz films and CVD growth of SiNWs. It will also contribute to the development of LIB anode materials and fuel cell catalysts.