Analysis Of Molybdenum Disulfide Nanomaterials Using Electron Microscopy

Monolayer molybdenum disulfide nanomaterial is a two dimensional material analogous to graphene.While graphene is a zero band gap semi-metal,monolayer molybdenum disulfide has a direct band gap of 1.9 eV,which makes it more suitable than graphene for electronic devices like transistors.To analyze the precise atomic structures of molybdenum disulfide nanomaterials,one needs the resolution down to a few angstroms.A rather commonly used analysis method is the transmission electron microscopy,which is the method we choose to use in this thesis.The thesis mainly contains three parts:The first part is the theoretical deduction of the structure factor of nanotubes.This part includes two parts: the deduction of carbon nanotube's structure factor and selection rule through convolution of helixes and discrete plane set,as well as the deduction of the constraints of normal two dimensional lattices to form a nanotube,including five possible two dimensional lattices.The second part is a diffraction analysis of two molybdenum disulfide nanosheets: the author developed an experimental method and a geometrical model to analyze the dihedral angle between two molybdenum nanosheets,the experimental method includes taking electron diffraction pattern at different tilt angles and the geometrical model gives the equations describing the geometry of the two nanosheets.The third part is the discussion and analysis of the experimental methods and characterization results used to grow molybdenum disulfide nanotubes,molybdenum disulfide nanosheets as well as the intercalation compound of graphene and tungsten disulfide.