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dc.contributor.advisorTung, Vincent
dc.contributor.authorAljarb, Areej
dc.date.accessioned2021-03-17T06:39:03Z
dc.date.available2021-03-17T06:39:03Z
dc.date.issued2021-01-17
dc.identifier.citationAljarb, A. (2021). Orientation and Dimensionality Control of Two-dimensional Transition Metal Dichalcogenides. KAUST Research Repository. https://doi.org/10.25781/KAUST-5KO52
dc.identifier.doi10.25781/KAUST-5KO52
dc.identifier.urihttp://hdl.handle.net/10754/668111
dc.description.abstractTwo-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted significant attention owing to their unique electrical, optical, mechanical, and thermal properties not found in their 3D counterparts. They can be obtained by mechanical, chemical, or electrochemical exfoliation. However, these strategies lack uniformity and produce defect-rich samples, making it impossible for large-scale device fabrication. Chemical vapor deposition (CVD) method emerges as the viable candidate to create atomically thin specimens at the technologically relevant scale. However, the large-scale growth of monolayer TMD films with spatial homogeneity and high electrical performance remains an unsolved challenge. The spatial inhomogeneity and the associated grain boundaries between randomly oriented domains culminate to the deleterious quality of TMDs, breaking of the long-range crystalline periodicity and introduction of insidious strain. Recent research efforts have therefore dedicated to obtaining the single crystallinity of 2D materials by controlling the orientation and dimensionality to obtain a large-scale and grain boundary-free monolayer films for Si-comparable electron mobility and overcoming the scaling limitation of traditional Si-based microelectronics,. In the first part of this thesis, orientation and dimensionality controlling of TMDs are discussed. To this end, we systematically study the growth of stereotypical molybdenum disulfide (MoS2) monolayer on a c-plane sapphire with CVD to elucidate the factors controlling their orientation. We have arrived at the conclusion that the concentration of precursors- that is, the ratio between sulfur and molybdenum oxide, plays a key role in the size and orientation of seeds, subsequently controlling the orientation of MoS2 monolayers. Later, we demonstrate a ledge-directed epitaxy (LDE) of dense arrays of continuous, self-aligned, monolayer, and single-crystalline MoS2 nanoribbons on β-gallium (iii) oxide (β-Ga2O3) (100) substrates. LDE MoS2 nanoribbons have spatial uniformity over a long-range and transport characteristics on par with those seen in exfoliated benchmarks. In the second part, we theoretically reveal and experimentally determine the origin of resonant modulation of contrast as a result of the residual 3-fold astigmatism in modern scanning transmission electron microscopy (STEM) and its unintended impact on violating the power-law dependence of contrast on coordination modes between the transition metal and chalcogenide atoms.
dc.language.isoen
dc.subjectChemical vapor deposition
dc.subjectTransition metal dichalcogenide
dc.subjectNanoribbons
dc.titleOrientation and Dimensionality Control of Two-dimensional Transition Metal Dichalcogenides
dc.typeDissertation
dc.contributor.departmentPhysical Science and Engineering (PSE) Division
thesis.degree.grantorKing Abdullah University of Science and Technology
dc.contributor.committeememberAnthopoulos, Thomas D.
dc.contributor.committeememberHan, Yu
dc.contributor.committeememberLi, Lain-Jong
dc.contributor.committeememberKim, Jeehwan
thesis.degree.disciplineMaterials Science and Engineering
thesis.degree.nameDoctor of Philosophy
refterms.dateFOA2021-03-17T06:39:04Z
kaust.request.doiyes


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