In situ TEM investigation on the beam-driven mechanisms of Ag/Au nanoparticles at room temperature
File(s)
Author(s)
Li, Xiaoru
Type
Thesis
Abstract
Over the last few decades, there have been significant developments in the field of nanotechnology from theoretical prediction to industrial application. Nanofabrication or nanomanufacturing has become a hot area in the past few decades due to the rapid development of electronics which requires the improvement of extremely small-scale manufacturing techniques. A chip-used field-effect transistor (FET) has been produced with a minimum size of about 5 nm via a photolithography method. However, as a top-down manufacturing method, photolithography is indirectly accompanied by the waste of resources, environmental pollution, and difficulty in recycling. There is a need to develop a more direct bottom-up technique at the nanoscale similar to macro-scale printing and additive manufacturing (AM).
Improving characterization techniques provides an opportunity to observe events happening at the nanoscale. With increasing research in nano-experiments, many studies have recognized the difficulty of finding a satisfactory agreement between classical theory and results for small-sized nanoparticles (NPs). This requires a better understanding of the intrinsic mechanisms and inter-particle reactions between and among nanoparticles. It has been found that an electron beam can be utilized to induce the coalescence of NPs and directly control the movement of nanoclusters in the liquid reservoir in a TEM. Such expositions are unsatisfactory because NPs were performed in a liquid, and it is hard to clarify whether the findings were caused by the surrounding liquid phase or affected by the fundamental mechanisms of NPs themselves. In this study, we observed beam-driven events of solid-state NPs to remove any possible effect of liquid, capping agents, and ligands, for a better understanding of the intrinsic mechanisms of NPs.
A systematic study of how the nano-deposition system contributes to the generation of NPs is still lacking. The nanoparticles' nucleation, growth, and deposition will be discussed in the work for obtaining size-controlled NPs. NPs (up to 15 nm in diameter) will be investigated via TEM for a better understanding of the intrinsic mechanisms of solid-state small-sized NPs. In-depth studies will be carried out focusing on beam-driven events of NPs, such as coalescence, Ostwald ripening, evaporation-condensation, and wetting. Moreover, the lattice reconstruction, shape evolution, and neck growth of NPs during coalescence will be also studied in situ in a TEM. These studies confirmed the possibility of using an electron beam to directly control the particle movement and realign the crystal of the nanostructure. The beam-driven coalescence of NPs will potentially benefit self-assembly and nanofabrication in the future, and in this work, nanocubes and nanorods were successfully created using beam manipulation.
Improving characterization techniques provides an opportunity to observe events happening at the nanoscale. With increasing research in nano-experiments, many studies have recognized the difficulty of finding a satisfactory agreement between classical theory and results for small-sized nanoparticles (NPs). This requires a better understanding of the intrinsic mechanisms and inter-particle reactions between and among nanoparticles. It has been found that an electron beam can be utilized to induce the coalescence of NPs and directly control the movement of nanoclusters in the liquid reservoir in a TEM. Such expositions are unsatisfactory because NPs were performed in a liquid, and it is hard to clarify whether the findings were caused by the surrounding liquid phase or affected by the fundamental mechanisms of NPs themselves. In this study, we observed beam-driven events of solid-state NPs to remove any possible effect of liquid, capping agents, and ligands, for a better understanding of the intrinsic mechanisms of NPs.
A systematic study of how the nano-deposition system contributes to the generation of NPs is still lacking. The nanoparticles' nucleation, growth, and deposition will be discussed in the work for obtaining size-controlled NPs. NPs (up to 15 nm in diameter) will be investigated via TEM for a better understanding of the intrinsic mechanisms of solid-state small-sized NPs. In-depth studies will be carried out focusing on beam-driven events of NPs, such as coalescence, Ostwald ripening, evaporation-condensation, and wetting. Moreover, the lattice reconstruction, shape evolution, and neck growth of NPs during coalescence will be also studied in situ in a TEM. These studies confirmed the possibility of using an electron beam to directly control the particle movement and realign the crystal of the nanostructure. The beam-driven coalescence of NPs will potentially benefit self-assembly and nanofabrication in the future, and in this work, nanocubes and nanorods were successfully created using beam manipulation.
Version
Open Access
Date Issued
2022-12
Date Awarded
2023-07
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Payne, David
Saiz, Eduardo
Publisher Department
Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)