利用聚焦離子束顯微鏡製作新型態之平面視角穿透式電子顯微鏡試片及其應用：石墨烯堆疊型態分析

Abstract

聚焦離子束顯微鏡(Focused ion beam, FIB)是一個多功能且強大的材料分析及試片製備儀器，被廣泛用來製作高品質的穿透式電子顯微鏡(Transmission electron microscopy, TEM)之橫截面(Cross-sectional)試片，其試片具有定點操作、厚度均勻且薄、可觀察區域大等特性。然而，FIB製作之平面視角(Plan-view)試片卻鮮少有文獻研究，並且現有的方法都會對試片表面造成汙染及破壞，不適用於二維奈米薄膜材料上。為改善現有分析技術的不足之處，本論文提出了利用FIB製作新型態平面視角的TEM試片，成功地應用於單層石墨烯系統，並經過電子繞射、高解析TEM影像以及歐傑電子譜儀(Auger electron microscopy)的分析證實試片沒有明顯的汙染與破壞產生。本論文也利用平面視角的TEM繞射分析、拉曼光譜儀(Raman spectroscopy)、以及橫截面高解析TEM來分析石墨烯的層數及堆疊型態，發現實驗結果與過去文獻所觀察的不一致，結果顯示對於二維奈米薄膜材料的微結構或許還有許多探討的空間。

Focused ion beam(FIB)is a versatile and powerful instrument for materials analysis and sample preparation, and is widely used to fabricate cross-sectional TEM specimens with site-specific preparation, uniform-thinckness, and large observation area. However, on the other hand, FIB-based preparation methods for plan-view specimens are seldom reported yet, and the proposed methods would damage the sample surface during FIB process, harmful to two-dimensional atomic layer materials, such as graphene, MoS2, etc. In this study, we propose a new plan-view TEM specimen preparation method using FIB, which is suitable for single-layer graphene. The results of electron diffraction analysis, high-resolution TEM, and Auger electron microscopy show that the sample surface remains clean and structural-pristine after the fabrication process. We also judge the stacking type and layer number of graphene by plan-view TEM analysis, Raman spectroscopy and high-resolution cross-sectional TEM analysis. We find that determinatnion of the layer numbers of a graphene sheet by Raman analysis is not consistent with the way reported in literatures. Further analysis is still required for understanding the microstructure of two-dimensional atomic layer materials.