Symmetry and Interface Consideration for Interactions on MoS2
Thesis Defense
1:30 pm –
3:30 pm
Jorgensen Hall Room: 207
Contact:
Physics Department, (402) 472-2770, paoffice@unl.edu
Prescott Evans will present his thesis defense, “Symmetry and Interface Considerations for Interactions on MoS2.” This event will be streamed live without an audience, in closed session with Zoom.
Join Zoom Meeting: https://unl.zoom.us/j/540955037
Meeting ID: 540 955 037
ABSTRACT: The critical role of symmetry, in adsorbate-MoS2 interactions, has been demonstrated through a variety of electronic structure, topology, and catalytic studies of MoS2 and MoS2 composites. A combination of density functional theory and experiment exhibiting diiodobenzene isomer dependent adsorption rates highlight frontier orbital symmetry as key to adsorption on MoS2. It is clear that the geometry and symmetry of MoS2 take part in the creation and stability of surface defects, influencing catalytic activity and application. We have shown that surface reactions can create such defects, as through methanol to methoxy reactions on MoS2. From experiment, it is clear moving forward, if there is to be a better understanding of reactions and catalysis, theory must include further considerations of frontier orbital symmetry and band structure. Extensive electronic band structure studies have shown bulk MoS2 differs from the monolayer as observed with other transition metal dichalcogenides (TMDs). To this difference in electronic structure, bulk MoS2 has the volume that permits defect removal by annealing, while defects will persist for monolayer MoS2. Further differences in the electronic behavior of monolayer and bulk MoS2 are illustrated by interactions with adsorbed metals. Experiments show metal to bulk TMD interactions exhibit electronic behavior fitting the expected conventional models while monolayer to metal interactions show a distinctly opposite trend. Undoubtedly, more complete interaction theory on MoS2 and other TMDs will require a better detailing of the difference in band structure between monolayer and bulk. Monolayer MoS2 and other monolayer material are generally accompanied by an underlying substrate. The influence of these underlying substrates on the monolayer systems must also be accounted for in theory including the addition of band bending and interface charge transfer effects. More complete theory which includes underlying mechanisms of frontier orbital symmetry in addition to monolayer and bulk electronic properties is necessary for accurately predicting the catalytic behavior and application of TMDs.
Join Zoom Meeting: https://unl.zoom.us/j/540955037
Meeting ID: 540 955 037
ABSTRACT: The critical role of symmetry, in adsorbate-MoS2 interactions, has been demonstrated through a variety of electronic structure, topology, and catalytic studies of MoS2 and MoS2 composites. A combination of density functional theory and experiment exhibiting diiodobenzene isomer dependent adsorption rates highlight frontier orbital symmetry as key to adsorption on MoS2. It is clear that the geometry and symmetry of MoS2 take part in the creation and stability of surface defects, influencing catalytic activity and application. We have shown that surface reactions can create such defects, as through methanol to methoxy reactions on MoS2. From experiment, it is clear moving forward, if there is to be a better understanding of reactions and catalysis, theory must include further considerations of frontier orbital symmetry and band structure. Extensive electronic band structure studies have shown bulk MoS2 differs from the monolayer as observed with other transition metal dichalcogenides (TMDs). To this difference in electronic structure, bulk MoS2 has the volume that permits defect removal by annealing, while defects will persist for monolayer MoS2. Further differences in the electronic behavior of monolayer and bulk MoS2 are illustrated by interactions with adsorbed metals. Experiments show metal to bulk TMD interactions exhibit electronic behavior fitting the expected conventional models while monolayer to metal interactions show a distinctly opposite trend. Undoubtedly, more complete interaction theory on MoS2 and other TMDs will require a better detailing of the difference in band structure between monolayer and bulk. Monolayer MoS2 and other monolayer material are generally accompanied by an underlying substrate. The influence of these underlying substrates on the monolayer systems must also be accounted for in theory including the addition of band bending and interface charge transfer effects. More complete theory which includes underlying mechanisms of frontier orbital symmetry in addition to monolayer and bulk electronic properties is necessary for accurately predicting the catalytic behavior and application of TMDs.