Advanced Interface Analysis in 2D Materials-Based Electronic Devices Using Cross-sectional Transmission Electron Microscopy

Abstract

Since the discovery of graphene, 2-dimensional (2D) semiconductors like graphene oxide (GO) and transition metal dichalcogenide (TMDCs) have attracted much attention as future potential electronic devices such as field-effect transistors (FETs) and resistive random access memory (RRAM), due to their unique electrical properties. In both electronic device systems, the metal electrodes are always used to make electrical contacts (source and drain contacts/Top and bottom electrodes). It is well known that the electrical performance is also dependent on the interface structures between metals and 2D semiconductors. To characterize these regions and reveal the operation mechanisms, transmission electron microscopy (TEM) has been considered as one of the powerful tools. Recently, the advanced TEM equipped with a spherical aberration corrector has been introduced and actively used for uncovering the atomic-scale structure and chemical composition of nano-materials with various dimensions (from 0D to 3D) in a sub-Å level. In particular, the cross-sectional TEM analysis combined with well-prepared TEM samples is needed for multi-stacked thin film structures. In this talk, I will present various cross-sectional (S)TEM works which were performed using advanced (S)TEM combined with a focused ion beam (FIB) sample preparation technique. The direct observation of metallic nanofilaments formed at the interface regions in Al/GO/Al and Au/GO/Al bipolar resistive memory devices will be shown. In addition, the ultraclean van der Waals contacts between indium-gold alloyed metal and monolayer MoS2 in field-effect transistors (FETs) will be discussed.