Mechanisms of electron-induced reactions in focused electron beam induced deposition (FEBID)

挥发性前体分子的电子诱导化学是聚焦电子束诱导沉积（FEBID）的核心，FEBID是用于纳米纤维的非常有前途的直接沉积技术，能够产生亚10 nm尺寸的独立3D结构。在FEBID中，最初为化学气相沉积（CVD）开发的挥发性且通常为有机金属的前体分子通过紧密聚焦的电子束在表面上分解。理想地，束将诱导前体的完全解离，使得期望的材料，例如，具有明确化学计量的金属或氧化物保留在表面，而分子的有机配体或其片段解吸。实际上，大量的配体材料经常残留下来并使存款的性质恶化。例如，芳族配位体如NH4难以除去并产生不期望的碳基质。尽管它们具有良好的挥发性，但这样的前体因此被认为不适合在FEBID中制造纯金属沉积物。然而，添加的工艺气体可以显著降低碳含量。该项目旨在确定这种纯化中涉及的电子诱导反应，并将评估这种化学方法是否对更广泛的前体有效。这将实现通过使用或用芳族配体改性容易获得的挥发性前体来开发更好的FEBID前体的目标策略。

Electron-induced chemistry of volatile precursor molecules is central to Focused Electron Beam Induced Deposition (FEBID), a very promising direct deposition technique for nanofabrication, capable of producing free-standing 3D structures of sub-10 nm size. In FEBID volatile and often organometallic precursor molecules, initially developed for chemical vapour deposition (CVD), are decomposed on a surface by a tightly focussed electron beam. Ideally, the beam would induce complete dissociation of the precursor so that the desired material, e.g., a metal or an oxide with well-defined stochiometry, remains at the surface while the organic ligands of the molecule or fragments thereof desorb. In reality, a significant amount of ligand material often remains behind and deteriorates the properties of the deposit. Aromatic ligands such as cyclopentadienyl, for instance, are difficult to remove and yield an undesired carbon matrix. Despite their favourable volatility, such precursors are thus considered unsuitable for fabrication of pure metal deposits in FEBID. However, added process gases can significantly reduce the carbon content. This project aims at identifying the electron-induced reactions involved in this purification and will evaluate if this chemistry is efficient for a wider range of precursors. This would enable a targeted strategy for development of better FEBID precursors by using or modifying readily available volatile precursors with aromatic ligands.