Mono-to-few Layers Transition Metal Dichalcogenides, Exciton Dynamics, and Versatile Growth of Naturally Formed Contacted Devices

Mono-to-few Layers Transition Metal Dichalcogenides, Exciton Dynamics, and Versatile Growth of Naturally Formed Contacted Devices

Bibliographic Details
Main Author: ALEITHAN, SHROUQ H.
Language:English
Published: Ohio University / OhioLINK 2018
Subjects:
Physics
Materials Science
Two dimensional materials
Transition Metal Dichalcogenides
Monolayer
Few layers
CVD growth
Exciton dynamics
Broadband femtosecond transient absorption spectroscopy
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1522165070034846
id ndltd-OhioLink-oai-etd.ohiolink.edu-ohiou1522165070034846
record_format oai_dc
collection NDLTD
language English
sources NDLTD
topic Physics
Materials Science
Two dimensional materials
Transition Metal Dichalcogenides
Monolayer
Few layers
CVD growth
Exciton dynamics
Broadband femtosecond transient absorption spectroscopy
spellingShingle Physics
Materials Science
Two dimensional materials
Transition Metal Dichalcogenides
Monolayer
Few layers
CVD growth
Exciton dynamics
Broadband femtosecond transient absorption spectroscopy
ALEITHAN, SHROUQ H.
Mono-to-few Layers Transition Metal Dichalcogenides, Exciton Dynamics, and Versatile Growth of Naturally Formed Contacted Devices
author ALEITHAN, SHROUQ H.
author_facet ALEITHAN, SHROUQ H.
author_sort ALEITHAN, SHROUQ H.
title Mono-to-few Layers Transition Metal Dichalcogenides, Exciton Dynamics, and Versatile Growth of Naturally Formed Contacted Devices
title_short Mono-to-few Layers Transition Metal Dichalcogenides, Exciton Dynamics, and Versatile Growth of Naturally Formed Contacted Devices
title_full Mono-to-few Layers Transition Metal Dichalcogenides, Exciton Dynamics, and Versatile Growth of Naturally Formed Contacted Devices
title_fullStr Mono-to-few Layers Transition Metal Dichalcogenides, Exciton Dynamics, and Versatile Growth of Naturally Formed Contacted Devices
title_full_unstemmed Mono-to-few Layers Transition Metal Dichalcogenides, Exciton Dynamics, and Versatile Growth of Naturally Formed Contacted Devices
title_sort mono-to-few layers transition metal dichalcogenides, exciton dynamics, and versatile growth of naturally formed contacted devices
publisher Ohio University / OhioLINK
publishDate 2018
url http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1522165070034846
work_keys_str_mv AT aleithanshrouqh monotofewlayerstransitionmetaldichalcogenidesexcitondynamicsandversatilegrowthofnaturallyformedcontacteddevices
_version_ 1719453450355343360
spelling ndltd-OhioLink-oai-etd.ohiolink.edu-ohiou15221650700348462021-08-03T07:05:31Z Mono-to-few Layers Transition Metal Dichalcogenides, Exciton Dynamics, and Versatile Growth of Naturally Formed Contacted Devices ALEITHAN, SHROUQ H. Physics Materials Science Two dimensional materials Transition Metal Dichalcogenides Monolayer Few layers CVD growth Exciton dynamics Broadband femtosecond transient absorption spectroscopy Two-dimensional atomic crystals of transition metal dichalcogenides (TMDs) have attracted great attention due to their diverse and potentially useful electronic and optical properties. Many TMD monolayer materials are considered excellent candidates for ultrasensitive photodetectors, valleytronics, transistors, and energy harvesting devices. Advancement can be made through an understanding of the excitonic band structure, excitonic binding energy, multi excitonicstates, and carrier dynamics in monolayer TMDs and their heterostructures. Additionally, the most important achievement along device application and manufacturing is having a good control of TMDs growth process and sample quality.A film of MoS<sub>2</sub> has been grown using CVD technique and characterized to identify monolayer area and the number of layers in different locations on the film. Carrier dynamics in monolayer have been investigated using broadband femtosecond transient absorption spectroscopy (FTAS). A tunable pump pulse was used while a broadband probe pulse revealed ground and excited state carrier dynamics. Interestingly, for pump wavelengths both resonant and non-resonant with the A and B excitons, a broad ground state bleach around 2.9 eV was observed, with decay components similar to A and B. Associating this bleach with the band nesting region between K and Γ in the band structure indicates significant k-space delocalization and overlap among excitonic wave functions identified as A, B, C, and D. Comparison of time dynamics for all features in resonance and non-resonance excitation is consistent with this finding.A novel technique to create self-contacted monolayer MoS<sub>2</sub> devices has been established by our group. In this technique, a pre-growth lithographical metallic patternserves as a seed for the TMD material to grow around and creates an electrical contact with the 2D layers. An adjusted growth method and components held at a high temperature lead to a versatile technique to create naturally formed contacted monolayer devices covering the four well-known TMD compounds (MoS<sub>2</sub>, MoSe<sub>2</sub>, WS<sub>2</sub>, and WSe<sub>2</sub>). This recent growth method improves our ability to grow high-quality monolayers on different patterns, large size devices, and different substrates. It results in excellent progress in the direction of the one-step production of multiple devices on one chip. Good and even distribution growth over 1 to 2 cm<sup>2</sup> patterned chips has been achieved. The electrical characterization showed low channel resistance that differs with the 2D material.The naturally contacted growth has been advanced to create lateral heterostructures. In this technique, a pre-growth lithographical multi-metallic pattern (Mo-W) with a void in between the two metals serves as a seed for different TMDs material to grow. Each TMD attaches to the corresponding metal and extends to fill the gap in between the two metals meeting the other material to create a lateral interface in the middle. This new technique shows control of size, shape and location of the lateral heterostructure growth. Future work will focus on understanding the details of the heterojunction and continue to improve the process to produce precise junctions (MoS<sub>2</sub>/WS<sub>2</sub>, (MoSe<sub>2</sub>/WSe<sub>2</sub>), and (MoS<sub>2</sub>/WSe<sub>2</sub>). 2018-06-06 English text Ohio University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1522165070034846 http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1522165070034846 unrestricted This thesis or dissertation is protected by copyright: some rights reserved. It is licensed for use under a Creative Commons license. Specific terms and permissions are available from this document's record in the OhioLINK ETD Center.

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