Synthesis of Bilayer Graphene and Hexagonal Boron Nitride by Chemical Vapor Deposition Method PDF Download

Author: Wenjing Fang (Ph. D.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 165

View

Book Description
The aim of this thesis is two-fold: the first is to develop a reliable method for synthesizing bilayer graphene using chemical vapor deposition (CVD) method and to understand the growth mechanism. The second part involves exploring methods of synthesizing hexagonal boron nitride (hBN). The successful isolation of monolayer graphene in 2004 has attracted many researchers to search for potential applications of graphene and other two-dimensional materials in electronic and optical devices. However, the Scotch-tape method sets contraints for such applications due to the limited size and randomized location of obtained flakes. Thus, synthesizing large-area, high-quality two dimensional materials is highly desirable. This thesis seeks to develop a method to produce both bilayers and hBN with large area by CVD method and to investigate the underlying growth mechanisms for better control over the thickness, uniformity and stacking orientation.

Author: Mengxi Liu
Publisher: Springer
ISBN: 981105181X
Category : Technology & Engineering
Languages : en
Pages : 106

View

Book Description
This thesis focuses on the energy band engineering of graphene. It presents pioneering findings on the controlled growth of graphene and graphene-based heterostructures, as well as scanning tunneling microscopy/scanning tunneling spectroscopy (STM/STS) studies on their electronic structures. The thesis primarily investigates two classes of graphene-based systems: (i) twisted bilayer graphene, which was synthesized on Rh substrates and manifests van Hove singularities near Fermi Level, and (ii) in-plane h-BN-G heterostructures, which were controllably synthesized in an ultrahigh vacuum chamber and demonstrate intriguing electronic properties on the interface. In short, the thesis offers revealing insights into the energy band engineering of graphene-based nanomaterials, which will greatly facilitate future graphene applications.

Author: Peter Michler
Publisher: Springer
ISBN: 3319563785
Category : Science
Languages : en
Pages : 457

View

Book Description
This book highlights the most recent developments in quantum dot spin physics and the generation of deterministic superior non-classical light states with quantum dots. In particular, it addresses single quantum dot spin manipulation, spin-photon entanglement and the generation of single-photon and entangled photon pair states with nearly ideal properties. The role of semiconductor microcavities, nanophotonic interfaces as well as quantum photonic integrated circuits is emphasized. The latest theoretical and experimental studies of phonon-dressed light matter interaction, single-dot lasing and resonance fluorescence in QD cavity systems are also provided. The book is written by the leading experts in the field.

Author: Hussain Ali Alsalman
Publisher:
ISBN:
Category :
Languages : en
Pages : 131

View

Book Description
Graphene is a leading two dimensional (2D) material with good technological potential. Currently, it is being scaled up in synthesis methods in order to meet future demands in technology markets. In this dissertation, a study of transferred epitaxial graphene (TEG) as a synthesis method, for large area monolayer and AB stacked bilayer Graphene, is presented. Monolayer epitaxial graphene (EG) is grown on the (0001) face of silicon carbide (SiC) in an argon atmosphere at a temperature of 1600 o C. Bilayer graphene can thereafter be synthesized if needed by intercalating the monolayer in a 100% hydrogen flow at 1050 oC to release what is known as the "buffer layer" into another graphene layer forming a bilayer. Either form of graphene can subsequently be transferred off the SiC substrate to mitigate the negative effects of the substrate. We develop a transfer process based on a gold adhesion layer and demonstrate for the first time, the transfer of high quality monolayer transferred epitaxial graphene (MTEG) and AB stacked bilayer transferred epitaxial graphene (BTEG). We use Raman characterization methods to determine the number and quality of graphene layers as well as orientation for bilayers which was made possible by contrast enhancement upon substrate transfer. We report these characteristics for the first time. Extensive structural characterization that have never been done before and were made possible by the successful transfer procedure, are presented in the Transmission Electron Microscopy (TEM) section. We successfully show suspended MTEG and BTEG samples which was never shown in literature before. We fabricate Transmission Line Measurement (TLM) structures to study the quality of the contact resistance for MTEG and BTEG. We report values in the range of 600 [OMEGA].[MICRO SIGN]m for MTEG and 2400 [OMEGA].[MICRO SIGN]m for BTEG. We also fabricate Field Effect Transistors (FETs) to study the field effect mobility and carrier concentration of MTEG and BTEG. We report average room temperature field effect mobility values of around 1700 cm2/V.s with best value of 2800 cm2/V.s for MTEG. This is over two times gain in mobility before transfer and is competitive with current leading synthesis methods. We measured the room temperature field effect mobility of BTEG to be 250 cm2/V.s on average and with a best value of 335 cm2/V.s. To the knowledge of the author, there are no reports in literature on the measured mobility of BTEG. We carry out annealing studies at argon ambient of 300 oC for TEG and show unique properties for BTEG in which a demonstrated ten orders of magnitude, higher moisture absorption than MTEG is shown. A section in this dissertation will be dedicated to related work on chemical vapor deposition (CVD) hexagonal boron nitride (h-BN) which is a complimentary 2D material to graphene. Improvements on CVD growth by electropolishing the copper substrate will be demonstrated where root mean square (RMS) surface roughness of starting material is reduced from 177 nm to 12 nm, considerably improving subsequent h-BN CVD growth. A procedure for the transfer of CVD graphene onto CVD h-BN as well as fabrication of Van der Paw structures will be presented. We show initial results of improvements in mobility when CVD h-BN is used as a substrate for CVD graphene.

Author: Inamuddin
Publisher: John Wiley & Sons
ISBN: 111965520X
Category : Technology & Engineering
Languages : en
Pages : 400

View

Book Description
Ever since the discovery of graphene, two-dimensional layered materials (2DLMs) have been the central tool of the materials research community. The reason behind their importance is their superlative and unique electronic, optical, physical, chemical and mechanical properties in layered form rather than in bulk form. The 2DLMs have been applied to electronics, catalysis, energy, environment, and biomedical applications. The following topics are discussed in the book’s fifteen chapters: • The research status of the 2D metal-organic frameworks and the different techniques used to synthesize them. • 2D black phosphorus (BP) and its practical application in various fields. • Reviews the synthesis methods of MXenes and provides a detailed discussion of their structural characterization and physical, electrochemical and optical properties, as well as applications in catalysis, energy storage, environmental management, biomedicine, and gas sensing. • The carbon-based materials and their potential applications via the photocatalytic process using visible light irradiation. • 2D materials like graphene, TMDCs, few-layer phosphorene, MXene in layered form and their heterostructures. • The structure and applications of 2D perovskites. • The physical parameters of pristine layered materials, ZnO, transition metal dichalcogenides, and heterostructures of layered materials are discussed. • The coupling of graphitic carbon nitride with various metal sulfides and oxides to form efficient heterojunction for water purification. • The structural features, synthetic methods, properties, and different applications and properties of 2D zeolites. • The methods for synthesizing 2D hollow nanostructures are featured and their structural aspects and potential in medical and non-medical applications. • The characteristics and structural aspects of 2D layered double hydroxides (LDHs) and the various synthesis methods and role of LDH in non-medical applications as adsorbent, sensor, catalyst, etc. • The synthesis of graphene-based 2D layered materials synthesized by using top-down and bottom-up approaches where the main emphasis is on the hot-filament thermal chemical vapor deposition (HFTCVD) method. • The different properties of 2D h-BN and borophene and the various methods being used for the synthesis of 2D h-BN, along with their growth mechanism and transfer techniques. • The physical properties and current progress of various transition metal dichalcogenides (TMDC) based on photoactive materials for photoelectrochemical (PEC) hydrogen evolution reaction. • The state-of-the-art of 2D layered materials and associated devices, such as electronic, biosensing, optoelectronic, and energy storage applications.

Author: Fei Hui
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

View

Book Description
Dielectrics are insulating materials used in many different electronic devices (e.g. capacitors, transistors, barristors), and play an important role in all of them. In fact, the dielectric is probably the most critical element in most devices, as it is exposed to electrical fields that can degrade its performance. In this PhD thesis I have investigated the use of monolayer and multilayer hexagonal boron nitride (h-BN) as dielectric for electronic devices, as it is a 2D material with a band gap of ̃5.9 eV. My work has mainly focused on the synthesis of the h-BN using chemical vapor deposition, the study of its intrinsic morphological and electrical properties at the nanoscale, and its performance as dielectric in different electronic devices, such as capacitors and memristors. We observe that monolayer and multilayer h-BN can be growth by CVD on Pt, Cu and Fe substrates. The main parameters affecting the growth of the h-BN are: i) a proper temperature determines the decomposition of the precursor. Lower temperatures will produce remaining particles and more defects in BN layer. ii) The flow rate of precursor/H2 influences the density of seeds. Excessive precursor will give rise to the formation of h-BN multilayer islands. iii) High vacuum and low pressure help to remove impurities in the tube furnace (e.g. oxygen, carbon), and therefore it produces better quality h-BN, i.e. uniform thickness with less defects. h-BN sheets grown on polycrystalline Pt substrates show different thicknesses depending on the crystallographic orientation at the surface of each Pt grain. This produces an undesired fluctuation on the leakage current from one Pt grain to another. However, the leakage current across the h-BN on the same Pt grain is very uniform, much more than that observed across amorphous HfO2 and TiO2 thin films. This phenomenon doesn't take place when growing the h-BN on Cu or Fe substrates. For example, the leakage current across h-BN grown on Cu substrates display small current variability among different Cu grains. The dielectric breakdown behavior in multilayer h-BN shows surface extrusion, similar to what happens in SiO2, HfO2 and Al2O3. However, monolayer h-BN keeps unaltered its structure even for harder breakdown events. The reason may be the extremely high thermal conductivity of monolayer h-BN. Multilayer h-BN shows random telegraph noise signals when applying constant voltage stresses, both at the device level and at the nanoscale. This strongly indicates the trapping and de-trapping of charges during the stress. This observation has been confirmed by the detection of charges at the dielectric breakdown location. The breakdown spot shows a singular ring-like structure that contains fixed negative charges, mobile negative charges, and positive fixed charges. The synthesis of h-BN on polycrystalline Fe substrates required longer cooling down times than when using Pt and Cu substrates. The reason is that the growth of h-BN on Fe substrates mainly takes place by surface precipitation mechanism, while on Pt and Cu substrates the mechanism is by surface-mediated reaction. Memristors with Ag/h-BN/Fe structure show both threshold resistive switching when the set is induced by applying positive voltage to the Ag electrode, and bipolar resistive switching when the set/reset processes are induced by applying negative/positive voltage to the Ag electrode. The reason should be that in threshold mode the filament is formed by Ag+ ions that penetrate in the h-BN stack, while in bipolar mode Fe+ ions penetrate in the h-BN stack. Ag+ ions show higher diffusivity than Fe+ ions and produce volatile switching.

Author: Wonbong Choi
Publisher: CRC Press
ISBN: 1439861889
Category : Science
Languages : en
Pages : 374

View

Book Description
Since the late 20th century, graphene-a one-atom-thick planar sheet of sp2-bonded carbon atoms densely packed in a honeycomb crystal lattice-has garnered appreciable attention as a potential next-generation electronic material due to its exceptional properties. These properties include high current density, ballistic transport, chemical inertness,

Author: Farzaneh Mahvash Mohammadi
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description
"Graphene is an allotrope of carbon in the form of a two-dimensional (2D) material with zero bandgap. Hexagonal boron nitride (hBN), also known as white graphite, is a wide bandgap 2D material that has found use as an insulating dielectric layer in ultra-high mobility graphene devices, 2D heterostructures and tunneling devices. In this thesis, we report the chemical vapor deposition (CVD) growth and characterization of graphene and monolayer hBN. The growth of graphene and hBN was performed separately in a tube furnace on Cu foils using methane (CH4) and an ammonia borane (NH3-BH3) precursor, respectively. Raman spectroscopy confirmed that the CVD grown graphene is a monolayer of high quality. We have fabricated graphene field effect transistors and characterized their electrical properties to demonstrate material quality. Additionally, the CVD grown graphene was incorporated in a diverse range of applications, including large area graphene ion sensitive field effect transistors, suspended graphene varactors and an investigation of the role of hydrogenation on the electronic and thermal properties of graphene. We employed a variety of techniques to characterize CVD grown hBN. The morphology of the as-grown film along with the optimization of growth conditions to yield high coverage of monolayer hBN was studied by scanning electron microscopy. X-ray photoelectron spectroscopy confirmed the presence of boron and nitrogen in the CVD grown film as well as the expected stoichiometry. The electron diffraction pattern of suspended hBN films displayed a hexagonal crystal structure. A prominent Stokes Raman shift at 1369 cm-1 was observed in hBN transferred to Si/SiO2 substrates, revealing that our CVD grown hBN is of monolayer form. The optical properties of our hBN layers were probed by cathodoluminescence and UV-visible absorption spectroscopy. We report the first observation of in-plane charge transport in large area CVD grown monolayer hBN using a variety of electrode geometries. Ni electrodes were used to provide electrical contacts. We have observed a quadratic scaling of current with voltage at high bias corresponding to a space charge limited conduction mechanism, with a room temperature mobility reaching up to 0.01 cm2/Vs at electric fields up to 100 kV/cm in the absence of dielectric breakdown. The observation of in-plane charge transport highlights the semiconducting nature of monolayer hBN, and identifies hBN as a wide-gap 2D crystal capable of supporting charge transport at high field. Furthermore, we have examined the suitability of CVD grown monolayer hBN for inhibiting corrosion. Quantitative measurements of monolayer hBN as a Cu corrosion inhibitor were studied by use of cyclic voltammetry, Tafel analysis and electrochemical impedance spectroscopy. We have found that CVD grown monolayer hBN reduces the Cu corrosion rate by one order of magnitude compared to bare Cu, suggesting that this ultrathin layer can be employed as an atomically thin corrosion-inhibition coating.The final contribution of this thesis is the growth of hBN directly on Si/SiO2 substrate via CVD. The main focus of this work is to produce metal-free, large-area, continuous and uniform hBN dielectric films on Si-based substrates ready to incorporate into devices without any transfer processing. We have also examined the effect of carrier gas flow rate on the thickness and roughness of the grown film in atmospheric pressure CVD. We have succeeded to grow large area hBN films with the thickness of ~ 2 nm and rms roughness of 0.6 nm (over 1 μm2) directly on Si/SiO2 substrates via atmospheric pressure CVD." --

Author: Mahmood Aliofkhazraei
Publisher: CRC Press
ISBN: 1466591382
Category : Science
Languages : en
Pages : 592

View

Book Description
Examines the Low Resistivity, High Mobility, and Zero Bandgap of GrapheneThe Graphene Science Handbook is a six-volume set that describes graphene's special structural, electrical, and chemical properties. The book considers how these properties can be used in different applications (including the development of batteries, fuel cells, photovoltaic

Author: Phaedon Avouris
Publisher: Cambridge University Press
ISBN: 1316738132
Category : Technology & Engineering
Languages : en
Pages : 521

View

Book Description
Learn about the most recent advances in 2D materials with this comprehensive and accessible text. Providing all the necessary materials science and physics background, leading experts discuss the fundamental properties of a wide range of 2D materials, and their potential applications in electronic, optoelectronic and photonic devices. Several important classes of materials are covered, from more established ones such as graphene, hexagonal boron nitride, and transition metal dichalcogenides, to new and emerging materials such as black phosphorus, silicene, and germanene. Readers will gain an in-depth understanding of the electronic structure and optical, thermal, mechanical, vibrational, spin and plasmonic properties of each material, as well as the different techniques that can be used for their synthesis. Presenting a unified perspective on 2D materials, this is an excellent resource for graduate students, researchers and practitioners working in nanotechnology, nanoelectronics, nanophotonics, condensed matter physics, and chemistry.