| Summary: | 博士 === 國立交通大學 === 材料科學與工程學系所 === 107 === In this thesis, we focus on the mechanisms of defect-free Cu nanowire (NW) growth and the surface modification of Cu NW by electron beam (e-beam) irradiation. There are three parts as discussed below. The first part, we investigate the heterogeneous nucleation of Cu droplet on the amorphous carbon (a-C) surface in high vacuum system, including the study of graphitization of a-C and the nucleation dynamic. The second part is the study of defect-free Cu NW synthesis and growth mechanism. The third part is the study of structural modification of Cu NW surface by e-beam irradiation-induced, including the oxide reduction and the atomically flat surface formation.
Owing to the rapid shrinkage of size in electronic devices, the fabrication and placement of high purity and low defect density nanometals, have been among the most important technological developments. In recent years, various studies of graphene nucleation on the Cu substrate rely to the stability and the low C solubility catalysts (<0.001 atomic %) in Cu. Therefore, in this study, we used the a-C film as the reaction foundation substrate of Cu nucleation to investigate the heterosurface characteristics and the migration/adsorption of Cu droplets under the ultra-high vacuum (UHV) system.
The fabrication and placement of high purity nanometals, such as one-dimensional copper (Cu) NWs, for interconnection in integrated devices have been among the most important technological developments in recent years. Structural stability and oxidation prevention have been the key issues, and the defect control in Cu NW growth has been found to be important. Therefore, in the second part, we report the synthesis of defect-free single-crystalline Cu NWs by controlling the surface-assisted heterogeneous nucleation of Cu atomic layering on the graphite-like loop. Without a metal-catalyst or induced defects, the high quality Cu NWs formed with high aspect ratio and high growth rate of 578 nm/s. The study illuminates the new mechanism by heterogeneous nucleation control and laying the groundwork for better understanding of heterosurface-assisted nucleation of defect-free Cu NW on a-C lacey film.
Recently, electron beam (e-beam) has been developed for nanomaterial observation and moreover as a functional modification technique. In the third part, we demonstrate the reduction of cuprous oxide (Cu2O) and the formation of an atomically flat surface on a Cu NW by e-beam irradiation-induced. In order to gain a deeper understanding of e-beam irradiation, we investigate the relation between e-beam irradiation and the atomic surface. Through the density functional theory (DFT) simulation of atomic sputtering, an obvious disparity in the sputtering threshold has been found under different structural conditions which leads the different structural evolutions. Both surface oxide reduction and atomic surface flattening induced have been identified as self-limiting and irreversible processes via in situ transmission electron microscope (TEM) observation. In addition, we found the formation of atomically flat surface is driven by the convergence of total surface energy under e-beam irradiation. With precise control, e-beam irradiation reveals huge potentials on atomic surface engineering.
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