Show simple item record

dc.contributor.authorLiu, Pengzi
dc.identifier.otherbibid: 9255274
dc.description.abstractThe layered transition metal dichalcogenide (TMD), 1T-tantalum disulfide (1T-TaS2) exhibits a range of electronic properties when cooled down, including phase transitions associated with charge-density-waves (CDWs), metal-insulator transitions as well as superconductivity upon doping or high pressure. The CDW phase transitions can be modulated by the thickness of 1T-TaS2. To understand the material's potential for electronic applications it is therefore important to identify the dimension and atomic layer stacking of 1T-TaS2 samples with both accuracy and precision. In this work, our goal is to develop a reliable method to extract the thickness and stacking sequence of 1T-TaS2 directly from experimentally recorded images. High-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) is a powerful method to image materials with atomic resolution. However, considering the two-dimensional nature of projected HAADF-STEM images, we choose the technique of convergent-beam electron diffraction (CBED) performed with atomically small electron beams from STEM. We show that combining experimental and simulated CBED patterns with rich information in the third-direction (i.e. thickness and stacking sequence) is an effective approach to study the structures of layered dichalcogenides. I will discuss the development of a method to extract the thickness and stacking sequence of exfoliated 1T-TaS2 layered structures directly from experimental CBED patterns and STEM images by comparison with simulation results. Starting with multislice simulations of both HAADF-STEM images and CBED patterns for 1T-TaS2 thickness and stacking sequence, I will demonstrate the influence on the image contrast. By comparison of these results with experimental data I show that the thickness of 1TTaS2 with simple stacking (all-A stacking) can be determined with a ± 1 unit cells uncertainty. Variations in the symmetry and the intensity distribution in CBED patterns can be used to distinguish simple all-A (AA….A) stacking from other stacking. Finally, I will briefly discuss the limitations of this method and future work. ii
dc.subjectTransmission electron microscopy
dc.subject1T-tantalum disulfide
dc.subjectImage simulations
dc.titleThickness And Stacking Sequence Determination Of 1T-Tantalum Disulfide Using Scanning Transmission Electron Microscopy
dc.typedissertation or thesis Physics University of Science, Applied Physics
dc.contributor.chairKourkoutis,Lena Fitting

Files in this item


This item appears in the following Collection(s)

Show simple item record