실시간 투과전자현미경을 이용하는 나노입자 분석 도구 개발

Abstract

최근 금 나노입자를 이용하여 다양한 성질의 나노구조체를 제작하고자 하는 노력이 있다. 나노구조체의 물리, 화학적 성질을 조절하기 위해서는 입자의 결정 구조 및 크기에 대한 예측이 필요한데, 이에 따라 입자의 성장 모델을 이해하는 것이 중요하다. 나노입자의 성장 모델 중 하나로 복수의 입자가 결합하는 Coalescence의 경우에는 명확한 이해가 정립되지 않아 계속해서 Coalescence에 대해 실시간 관찰하는 연구가 활발히 진행되고 있다. 이로 인해 고체상에서의 관찰은 Coalescence 과정 중에서 수반할 수 있는 다양한 현상들을 관찰하였다. 그러나 이러한 연구들은 현미경 해상도의 한계와 시편 준비 방법의 한계로 인해 충분히 성장한 이후의 Coalescence 과정만을 분석하였기 때문에 초기 단계의 Coalescence에 대해서는 정확히 관찰할 수 없었다. 또한 액체상에서는 현미경 내부 진공으로부터 액체가 증발하지 않도록 하는 스페이서 두께에 의한 전자빔 투과 문제를 극복하고자 2D 물질을 포개어 놓거나 마이크로제조공정을 이용하는 등의 노력이 있었지만 샘플을 균일하게 가두기 어렵고, 스페이서의 제작 재현성이 매우 낮기 때문에 균일하고 많은 샘플 분석을 하는 것에 대해 어려움이 있었다. 이에 따라 본 연구에서는 각 상에서 초기 단계 나노입자 Coalescence과정을, 더 높은 해상도를 바탕으로 하여 관찰하고자 하는 분석 도구를 개발 및 최적화하여, 고체 및 액체상에서의Coalescence 메커니즘에 대해 더 명확한 이해를 하기 위한 실험적 근거를 얻고자 연구를 진행하였다.|Recently, there has been much effort to fabricate nanostructures with various properties by using nanoparticles. In order to control the physical and chemical properties of nanostructures, it is necessary to be able to predict the crystal structure and size of the particles, and accordingly it is important to understand the growth models of the particles. In the case of coalescence, a growth model of nanoparticles where multiple particles combine, no clear comprehension has been established, and so real-time observation of coalescence continues to be actively studied. As a result, observations of coalescence on solid substrates have analyzed various phenomena that accompany the coalescence process. However, these studies were not able to accurately observe coalescence in its early stages due to limitations of microscopic resolution and methods of specimen preparation, so only the post-growth coalescence process could be observed. In addition, for better observation of coalescence in liquid samples, the problems of the sample fluid evaporating due to the microscope’s interior vacuum, and decreased electron beam transmission due to spacer thickness have been addressed, and efforts for better observation, such as stacking 2D materials together or using a micro-manufacturing process have been attempted. However, it is difficult for the samples to be distributed uniformly, and analyzing many samples quickly is not possible due to the exceedingly low reproducibility of the spacer. Accordingly, this study conducted experimental methods to develop and optimize the early stage nanoparticle coalescence processes of each phase with higher resolution to obtain a clearer understanding of the mechanisms in both solid and liquid coalescence.; Recently, there has been much effort to fabricate nanostructures with various properties by using nanoparticles. In order to control the physical and chemical properties of nanostructures, it is necessary to be able to predict the crystal structure and size of the particles, and accordingly it is important to understand the growth models of the particles. In the case of coalescence, a growth model of nanoparticles where multiple particles combine, no clear comprehension has been established, and so real-time observation of coalescence continues to be actively studied. As a result, observations of coalescence on solid substrates have analyzed various phenomena that accompany the coalescence process. However, these studies were not able to accurately observe coalescence in its early stages due to limitations of microscopic resolution and methods of specimen preparation, so only the post-growth coalescence process could be observed. In addition, for better observation of coalescence in liquid samples, the problems of the sample fluid evaporating due to the microscope’s interior vacuum, and decreased electron beam transmission due to spacer thickness have been addressed, and efforts for better observation, such as stacking 2D materials together or using a micro-manufacturing process have been attempted. However, it is difficult for the samples to be distributed uniformly, and analyzing many samples quickly is not possible due to the exceedingly low reproducibility of the spacer. Accordingly, this study conducted experimental methods to develop and optimize the early stage nanoparticle coalescence processes of each phase with higher resolution to obtain a clearer understanding of the mechanisms in both solid and liquid coalescence.