Study of 2D materials growth using Transmission Electron Microscopy

Two-dimensional atomically thin materials such as graphene are very promising materials for future applications.  Among them, 2D transition metal dichalcogenides (2D-TMDs), such as MoS₂ and MoSe₂, have attracted tremendous attention for their exceptional optical and electronic properties ranging from semiconducting, to metallic or superconducting. The physical properties of these 2D layers are first defined by elemental components but also critically depend on their structural qualities such as crystallinity, domain size, atomic defects, etc. Since a few years our team has been developing the fabrication of high quality 2D-TMDs by hetero-epitaxial growth using molecular beam epitaxy (MBE). This growth technique using single crystal substrate and high purity elemental sources might lead to well-oriented large crystal formation with a great flexibility in the choice of the metals and low contamination. To understand the growth mechanisms and further to achieve well-controlled high quality materials synthesis, multidimensional and multiscale structural analysis are essential. Aberration corrected transmission electron microscopy (AC-TEM) is one of the most powerful techniques to study the structure of atomically thin 2D layers, allowing structural analysis from micron down to atomic scale.

The aim of the internship will be to study the MBE based epitaxial growth of 2D-TMDs using AC-TEM techniques. For this purpose, the student will develop an analytical process to investigate the structural correlation between grown materials and growth substrate, requiring a combination of plan-view and cross-sectional analysis. The student will work mainly in the microscopy laboratory (LEMMA-IRIG) at Nano-characterization Platform (PFNC) and will also contribute to MBE experiments and other characterization techniques in the laboratory (SPINTEC) to get a more comprehensive view of the 2D systems studied.

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