Show simple item record

dc.contributor.advisorBunch, J. Scotten_US
dc.contributor.authorLloyd, Daviden_US
dc.date.accessioned2020-05-19T17:40:18Z
dc.date.available2020-05-19T17:40:18Z
dc.date.issued2020
dc.identifier.urihttps://hdl.handle.net/2144/41023
dc.description.abstractMonolayer molybdenum disulfide (MoS2) is a three-atom-thick direct band gap semiconductor, which has received considerable attention for use as a channel material in atomically thin transistors, photodetectors, excitonic LED’s, and many other potential applications. It is also a mechanically exceptional material with a large stiffness and flexibility, and can withstand very large strains (11%) before rupture. In this dissertation we investigated the mechanics of the stiffness and adhesion forces in atomically thin MoS2 membranes, and how biaxial strains can be used to induce large modulations in the band structure of the material. First, we used chemical vapor deposition (CVD) to grow MoS2 crystals that are highly impermeable to gas, and used a pressure difference across suspended membranes to induce large biaxial strains. We demonstrated the continuous and reversible tuning of the optical band gap of suspended monolayer membranes by as much as 500 meV, and induced strains of as much as 5.6% before rupture. We observed the effect of strain on the energy and intensity of the peaks in the photoluminescence (PL) and Raman spectra and found their linear strain tuning rates, then report evidence for the strain tuning of higher level optical transitions. Second, we determined the Young’s modulus and works of separation and adhesion of MoS2 membranes, and found that adhesion hysteresis is an important effect in determining the behavior of our systems. Finally, we investigated the use of atomically thin materials as nanofiltration membranes, by perforating the material with nanopores which selectively permit the transport of smaller molecules while rejecting larger ones. We studied ion transport through nanopores in graphene membranes and demonstrate that in-situ atomic force microscope measurements in liquid are a powerful way to reveal occlusions and contaminants around the pores - work which will aid future researchers in further unveiling the properties of these fascinating systems.en_US
dc.language.isoen_US
dc.subjectMechanical engineeringen_US
dc.subjectBand gap engineeringen_US
dc.subjectDelaminationen_US
dc.subjectImpermeableen_US
dc.subjectMechanical instabilityen_US
dc.subjectNanoporeen_US
dc.subjectStrain engineeringen_US
dc.titleEngineering with atomically thin materials: making crystal grains, strains, and nanoporous membranesen_US
dc.typeThesis/Dissertationen_US
dc.date.updated2020-05-19T04:02:20Z
etd.degree.nameDoctor of Philosophyen_US
etd.degree.leveldoctoralen_US
etd.degree.disciplineMechanical Engineeringen_US
etd.degree.grantorBoston Universityen_US
dc.identifier.orcid0000-0002-9828-6152


This item appears in the following Collection(s)

Show simple item record