Chemical Vapor Deposition Growth of Molybdenum Disulfide and Its Nanoscale Tribological Correlation with Raman Spectroscopy PDF Download
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Author: Sol Torrel
Publisher:
ISBN:
Category : Molybdenum disulfide
Languages : en
Pages : 176
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Book Description
In this doctoral thesis work, two-dimensional (2D) molybdenum disulfide (MoS2) single crystals have been synthesized, characterized, and tribologically studied. Specifically, detailed analyses of processes that occur during chemical vapor deposition (CVD) of atomically thin MoS2 have been performed to understand key mechanisms responsible for reproducible growth of high quality materials. To this end, literature survey of growth parameters was performed and compared with original experiments performed here. The methods and mechanisms of nucleation and growth of large-area, single- and few-layer MoS2 are described with emphasis on variable control and repeatability. The synthesis work performed here provides new insights into the challenges of reproducible MoS2 growth using CVD. Following the CVD work, the thesis research included phase transformation of MoS2 - building on ongoing research in our group. The aim of this part of the research was to understand how chemistry can change the structural phase of 2D MoS2. More specifically, this work was performed to determine the root cause of challenges that are encountered during phase transformation. Finally, my primary focus and most of my efforts were devoted to study of the tribological properties of 2D MoS2 to further develop fundamental understanding of friction on the atomic level. Atomic force microscopy (AFM) was used to measure nanoscale tribological properties of semiconducting and metallic monolayer MoS2 to study the influence of electronic structure on friction behavior. Furthermore, various multilayer semiconducting polytypes of MoS2 were studied to elucidate the phononic contribution to friction. Electronic and phononic properties of this nanomaterial were probed, analyzed, and correlated through AFM and Raman spectroscopy. As a result, a preliminary methodology for remote prediction of friction behavior via laser excitation has been developed.
Author: Sol Torrel
Publisher:
ISBN:
Category : Molybdenum disulfide
Languages : en
Pages : 176
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Book Description
In this doctoral thesis work, two-dimensional (2D) molybdenum disulfide (MoS2) single crystals have been synthesized, characterized, and tribologically studied. Specifically, detailed analyses of processes that occur during chemical vapor deposition (CVD) of atomically thin MoS2 have been performed to understand key mechanisms responsible for reproducible growth of high quality materials. To this end, literature survey of growth parameters was performed and compared with original experiments performed here. The methods and mechanisms of nucleation and growth of large-area, single- and few-layer MoS2 are described with emphasis on variable control and repeatability. The synthesis work performed here provides new insights into the challenges of reproducible MoS2 growth using CVD. Following the CVD work, the thesis research included phase transformation of MoS2 - building on ongoing research in our group. The aim of this part of the research was to understand how chemistry can change the structural phase of 2D MoS2. More specifically, this work was performed to determine the root cause of challenges that are encountered during phase transformation. Finally, my primary focus and most of my efforts were devoted to study of the tribological properties of 2D MoS2 to further develop fundamental understanding of friction on the atomic level. Atomic force microscopy (AFM) was used to measure nanoscale tribological properties of semiconducting and metallic monolayer MoS2 to study the influence of electronic structure on friction behavior. Furthermore, various multilayer semiconducting polytypes of MoS2 were studied to elucidate the phononic contribution to friction. Electronic and phononic properties of this nanomaterial were probed, analyzed, and correlated through AFM and Raman spectroscopy. As a result, a preliminary methodology for remote prediction of friction behavior via laser excitation has been developed.
Author: Zachary Durnell Ganger
Publisher:
ISBN:
Category : Chemical vapor deposition
Languages : en
Pages : 96
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Book Description
Graphene has successfully been a 2D material applied in various fields, but it is not the most appropriate candidate for many electronic devices unless its bandgap structure is tuned through functionalization. Among all other 2D material families, transition metal dichalcogenides (TMDs), represented by molybdenum disulfide (MoS2), are promising and emerging in power electronics due to their large direct bandgap and other electronic properties. 2D MoS2 has been fabricated through different approaches such as mechanical exfoliation, chemical etching, and chemical vapor deposition (CVD). The current major challenge in fabricating 2D MoS2 films is to produce a high-quality large-area monolayer film at a controlled condition. This thesis study is to grow 2D MoS2 films by CVD method at various experimental settings and to characterize the size, thickness, and morphology of the films, towards finding an optimal processing condition. Experimental settings for the growth parameters include the precursor amounts and placements, growth time, growth temperature, carrier gas flow rate, substrates, and seeding promoters. The growth films are characterized with the help of optical microscopy, Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and atomic force microscopy (AFM). It is found that 1) MoS2 growth is sensitive to the carrier flow rate and temperature; and 2) 2D MoS2 grain size and areal coverage are correlated with grow time as well as the distance from the promoter PTAS (perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt) resource. Existence of monolayer MoS2, in the presence of PTAS promotor, is confirmed with Raman Spectroscopy and AFM. Multilayer MoS2 films with grains up to several hundreds of micrometers, confirmed with optical microscopy, SEM and Raman, are successfully grown on clean Si/SiO2 substrate in the presence of PTAS promotor vapor in the vicinity. Growth of monolayer/multilayer MoS2 on sapphire and graphene was also demonstrated
Author: Dimitra Vernardou
Publisher: MDPI
ISBN: 3039439235
Category : Science
Languages : en
Pages : 94
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Book Description
Pursuing a scalable production methodology for materials and advancing it from the laboratory to industry is beneficial to novel daily-life applications. From this perspective, chemical vapor deposition (CVD) offers a compromise between efficiency, controllability, tunability and excellent run-to-run repeatability in the coverage of monolayers on substrates. Hence, CVD meets all of the requirements for industrialization in basically all areas, including polymer coatings, metals, water-filtration systems, solar cells and so on. The Special Issue “Advances in Chemical Vapor Deposition” is dedicated to providing an overview of the latest experimental findings and identifying the growth parameters and characteristics of perovskites, TiO2, Al2O3, VO2 and V2O5 with desired qualities for potentially useful devices.
Author: Pietro Mandracci
Publisher: BoD – Books on Demand
ISBN: 1789849608
Category : Technology & Engineering
Languages : en
Pages : 166
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Book Description
Chemical vapor deposition (CVD) techniques have played a major role in the development of modern technology, and the rise of nanotechnology has further increased their importance, thanks to techniques such as atomic layer deposition (ALD) and vapor liquid solid growth, which are able to control the growth process at the nanoscale. This book aims to contribute to the knowledge of recent developments in CVD technology and its applications. To this aim, important process innovations, such as spatial ALD, direct liquid injection CVD, and electron cyclotron resonance CVD, are presented. Moreover, some of the most recent applications of CVD techniques for the growth of nanomaterials, including graphene, nanofibers, and diamond-like carbon, are described in the book.
Author: Hung Duc Nguyen
Publisher:
ISBN:
Category : Chemical vapor deposition
Languages : en
Pages :
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Author: Nicholas Simonson
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Two-dimensional (2D) transition metal dichalcogenides (TMDs) have demonstrated promising proof-of-concept performance in electronic and optoelectronic applications. Aside from desirable electronic properties, TMDs also exhibit inherent flexibility and transparency due to their atomically thin nature. Fabrication of TMD-based nanoelectronics directly on transparent, flexible substrates remains a challenge due to the high processing temperatures required for synthesis of highly crystalline material, temperatures which are generally not compatible with industrially relevant multicomponent glasses such as flexible Willow Glass, LCD display Lotus Glass, and the ubiquitous Gorilla Glass. This dissertation addresses the limitations of TMD growth on glass by examining the impact of glass surface chemistry, synthesis parameters, and alkali ion species on the nucleation and growth of MoS2 and WSe¬2 using metalorganic chemical vapor deposition (MOCVD). Chapter 1 introduces the necessary background, overarching hypothesis, technical motivation, and relevant literature on low-temperature CVD, alkali-assisted CVD, and CVD-on-glass of TMDs. Chapter 2 discusses the requisite experimental methods, particularly the synthesis processes and characterization techniques used. Chapter 3 presents the findings regarding initial synthesis optimization of MoS2 and WSe2 as well as alkali-assisted CVD. Chapter 3 also presents findings regarding the effect of glass chemistry on low-temperature CVD of TMDs through use of alkali-containing glass and substrate surface treatment. Chapter 4 introduces a carbon-free H2S precursor to further improve domain size and electronic properties, and examines the benefits of a combined approach involving various alkali-containing glass chemistries, alkali halides, and H2S-based growth. Chapter 5 includes MoS2 synthesis of vertically oriented films for electrochemical catalysis and lateral MoS2-graphene heterostructures. Lastly, Chapter 6 discusses the implications and future work in the growth of device-quality TMDs directly on multicomponent glasses.
Author: Carl Morris Gross (III)
Publisher:
ISBN:
Category : Chemical vapor deposition
Languages : en
Pages : 40
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Book Description
Two-dimensional materials, or materials that are only one atomic layer thick, have seen much research in recent years because of their interesting electrical properties. The first of these materials, graphene, was found to have incredible electrical properties but lacked a bandgap in intrinsic films. Without a bandgap, graphene cannot create transistors that can be shut off. Molybdenum disulfide, however, is a two-dimensional semiconductor with a large bandgap. The main issue of molybdenum disulfide is that synthesized films are a much lower quality than their exfoliated counterparts. For molybdenum disulfide to be able to be used practically, a method of synthesis must be found that can reliably create quality large area monolayer films. In this thesis, three methods of molybdenum disulfide film synthesis are presented. Methods implemented used a tube furnace as a chemical vapor deposition system to evaporate source materials to synthesize thin films of molybdenum disulfide. An exploration into the different synthesis parameters shows optimal conditions for these specific methods. Then a discussion of these different methods is presented by judging films grown by using these methods on relevant criteria. This work shows methods to synthesize large area, polycrystalline, small grain, multilayer films, both intrinsic and doped, and to synthesize small area, single crystal and polycrystalline, monolayer films of molybdenum disulfide.
Author: Polly Wanda Chu
Publisher:
ISBN:
Category :
Languages : en
Pages : 434
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Book Description
Thin titanium dioxide films were produced by metalorganic chemical vapor deposition on sapphire(0001) in an ultrahigh vacuum (UHV) chamber. A method was developed for producing controlled submonolayer depositions from titanium isopropoxide precursor. Film thickness ranged from 0.1 to 2.7 nm. In situ X-ray photoelectron spectroscopy (XPS) was used to determine film stoichiometry with increasing thickness. The effect of isothermal annealing on desorption was evaluated. Photoelectron peak shapes and positions from the initial monolayers were analyzed for evidence of interface reaction. Deposition from titanium isopropoxide is divided into two regimes: depositions below and above the pyrolysis temperature. This temperature was determined to be 300 deg C. Controlled submonolayers of titanium oxide were produced by cycles of dosing with titanium isopropoxide vapor below and annealing above 300 deg C. Precursor adsorption below the pyrolysis temperature was observed to saturate after 15 minutes of dosing. The quantity absorbed was shown to have an upper limit of one monolayer. The stoichiometry of thin films grown by the cycling method were determined to be TiO2. Titanium dioxide film stoichiometry was unaffected by isothermal annealing at 700 deg C. Annealing produced a decrease in film thickness. This was explained as due to desorption. Desorption ceased at approximately 2.5 to 3 monolayers, suggesting bonding of the initial monolayers of film to sapphire is stronger than to itself. Evidence of sapphire reduction at the interface by the depositions was not observed. The XPS O is peak shifted with increased film thickness. The shifts were consistent with oxygen in sapphire and titanium dioxide having different O is photoelectron peak positions. Simulations showed the total shifts for thin films ranging in thickness of 0.1 to 2.7 nm to be -0.99 to -1.23 eV. Thick films were produced for comparison.
Author: Eui Sang Song
Publisher:
ISBN:
Category : Chemical vapor deposition
Languages : en
Pages : 96
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Author: Theodore M. Besmann
Publisher: The Electrochemical Society
ISBN: 9781566771559
Category : Science
Languages : en
Pages : 922
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