Exploring the fundamental mechanisms of highly strained structures on tungsten di selenide for optomechanical modulation
Zarin, Ishrat
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Permalink
https://hdl.handle.net/2142/121383
Description
Title
Exploring the fundamental mechanisms of highly strained structures on tungsten di selenide for optomechanical modulation
Author(s)
Zarin, Ishrat
Issue Date
2023-07-21
Director of Research (if dissertation) or Advisor (if thesis)
Miljkovic , Nenad
Department of Study
Mechanical Sci & Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
2D nanomaterials, Tungsten di selenide
Abstract
2D nanomaterials have intrigued the scientific community with functionalities that emerge with the small atomic thickness, otherwise, absent in the bulk counterparts. Modification and manipulation of these interesting functionalities are possible through altering mechanical and structural attributes. Strain engineering has emerged as a way to create and control interesting properties in 2D nanomaterials owing to the fact that these materials have an exceptional capability to withstand the high strain. strain can be introduced in such materials due to lattice mismatch or thermal expansions during fabrication or transfer to substrates. It can also be controllably induced by chemical procedures, mechanical deformations of substrates, electric current, pressurizing suspended layers etc. Strain modulation causes changes in the lattice, electronic, and optical structures resulting in high mobility, high thermal conductivity, high transparency, mechanical robustness and many other interesting physical phenomena. Studies have been reported with innovative ways of introducing strain in 2D nanomaterials, the following emergence of functionalities, and utilization of the fundamental realizations in devices. One of the widely investigated techniques for inducing strain is post buckling instability. Post buckling instabilities form when a film-substrate system goes through mismatch strain owing to the different stiffness of the materials. Additionally, these instabilities can introduce strain gradient that gives the scope to control the variation of intended properties. Wrinkles, crumples, ripples etc. have been widely studied in the field of 2D nanomaterials. Although highly investigated the proper understanding of the mechanics of post buckling instabilities in 2D materials and how they effect the properties of 2D materials is still lacking. Moreover, post buckling instabilities have been reported to induce high strain due to localization. As a result, these localized post buckling instabilities present plethora of opportunities when it comes to 2D nanomaterials. Especially, drastic modulation of properties hasn’t been possible due to experimental limitations, and high strain post buckling structures can be the way to overcome these limitations to inducing high strain into 2D nanomaterials. Here, we investigate different modes of post buckling instabilities which have localized aspects and the potential to induce very high strain in 2D nanomaterials. We show that using folds a highly localized form of post buckling structures, we can induce high strain in tungsten di selenide (WSe2) which can be utilized in different aspects of strain engineering.
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