Atomic-Scale Study of Nanostructure-Property Relationship by Transmission Electron Microscopy

Abstract

Nanostructure is widely accepted as a key factor that tailors the properties of materials. A thorough understanding of the relationship between material properties and nanostructure including the crystalline structure and electrical structure is the precondition to not only revealing the mystery of natural material but also manipulation and revolution of emerging materials. TEM serves as one of the most efficient and multifunctional instruments for such a purpose. Benefiting from the advancements in aberration correction, we could probe the physical world from the micrometer level down to the ever-growing sub-angstrom regime. Further equipped with various advanced spectrometers, TEM could realize collecting information simultaneously on the atomic scale about the local chemical species, valence state, electrical structure, and even the atomic dynamic behavior under a simulated real environment.

This dissertation starts with an introduction of the working principle and current development of TEM and equipped spectrometers, followed by the vital role of TEM in analyzing the nanostructure and structure-property relationship in the field of natural deep-sea shell and 2D material synthesis. Fundamental knowledge of typical 2D materials and the respective solid-state devices will be discussed for a better understanding of the structure-property relationship.

In the experimental technique section, different TEM sample-preparation methods, solid-state device fabrication processes, and transport measurement system are discussed in detail for a comprehensive study of the structure-property relationship.

In chapters 3 to 5, we emphasize the significance of unveiling the mystery of nature bio-structures. Nature owns amazing intelligence and bottom-up skills in designing and fabricating various nanocomposites with novel physical and chemical properties. From the top of mountains to the bottom of oceans, living beings keep synthesizing and refining life-related nanomaterials of much better functionalities and more complicated organic-inorganic-hybrid structures than their man-made counterparts. It’s highly inspirational to reveal the atomic-scale structural and compositional origins of unique properties, such as high-pressure resistance, optical transparency, and good thermal isolation. we conducted TEM, SEM, EDS, XRD, and FT-IR to report the shell microstructural features and chemical composition of several deep-sea shells from different areas. We further find natural existing single-metal-atom dispersion structure in the hot vent snail shell. Such structure could overcome the high surface energy of single atom dispersion and remain stable. We identify its distribution and accurate chemical structure by a series of techniques. It is proved that such structure has a selectivity to Fe element, and it also serves as the nuclei sites in the biomineralization process.

In Chapter 6 we proposed two effective synthesis methods, LPT methods for high-quality single crystal growth of bulk 2D materials and MSCS for atomically thin 2D materials growth. Few-layer sample exfoliated from LPT method synthesized 2D materials is fabricated into solid-state device and exhibits higher carrier mobility. While MSCS could realize the growth management of domain size, and layer number. We anticipate that the substantially enriched understanding of CVD growth kinetics and the innovative application of X:M-T growth diagram would effectively and scientifically pave the way for the growth management of all 2D TMDCs.