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Formation Of Graphene And Hexagonal Boron Nitride On Rh111 Studied By In Situ Scanning Tunnelling Microscopy
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Book Synopsis Formation of Graphene and Hexagonal Boron Nitride on Rh(111) Studied by In-situ Scanning Tunnelling Microscopy by : Guocai Dong
Download or read book Formation of Graphene and Hexagonal Boron Nitride on Rh(111) Studied by In-situ Scanning Tunnelling Microscopy written by Guocai Dong and published by . This book was released on 2012 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Controlled Synthesis and Scanning Tunneling Microscopy Study of Graphene and Graphene-Based Heterostructures by : Mengxi Liu
Download or read book Controlled Synthesis and Scanning Tunneling Microscopy Study of Graphene and Graphene-Based Heterostructures written by Mengxi Liu and published by Springer. This book was released on 2017-10-10 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Variable-Temperature Scanning Tunneling Microscopy Studies of Growth and Characterization of Hexagonal Boron Nitride and Graphene Layers by : Pedro Arias
Download or read book Variable-Temperature Scanning Tunneling Microscopy Studies of Growth and Characterization of Hexagonal Boron Nitride and Graphene Layers written by Pedro Arias and published by . This book was released on 2019 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-dimensional (2D) materials, such as graphene and hexagonal boron nitride (hBN) have attracted attention from both academia and industry owing to their unique atomically thin structure and associated properties. The goal of this dissertation is to provide fundamental insights of the growth kinetics, surface structure, and thermal stability of hBN and graphene layers grown via chemical vapor deposition (CVD) on metal substrates. Scanning tunneling microscopy (STM) was used to investigate the surface structure of hexagonal boron nitride (hBN) domains on Pd(111) grown via dissociative chemisorption of borazine on Pd(111)/Al2O3(0001) thin films. STM images acquired from the hBN/Pd(111) sample reveal moir patterns with different periodicities corresponding to rotational domains of hBN. Surface corrugations in each of the moir patterns were measured from the STM images as a function of the STM tunneling parameters. The corrugation amplitude z was found to depend on the tunneling bias and increases with increasing . The observed tunneling-parameter dependence in z were attributed to the electronic structure of the hBN/Pd(111) system. The domains with the largest , exhibit a bifurcation behavior in which some domains are nearly flat, and others develop "blisters", i.e., significant hills-and-valley geometric undulations. Hence, unlike any other monolayer hBN-on-metal system, hBN/Pd can have either mainly geometric or mainly electronic corrugation, depending on the domain orientation. The growth kinetics of hBN monolayers grown via CVD using borazine (B3N3H6) on Pd(111) were investigated using in situ variable-temperature STM. STM images were acquired during CVD of borazine on Pd(111) as a function of the substrate temperature T, the borazine partial pressure P, and time t. The STM images reveal a T and P dependent change in the growth mode: at higher P and lower T, (lower P and higher T), hBN nucleation occurs primarily on Pd step edges (Pd terraces). Furthermore, the mechanisms promoting growth across the step edges (as a carpet across steps) are identified. These results provide new insights into the nucleation and growth of hBN monolayers and potentially other 2D materials and related heterostructures on metal substrates. The thermal stability of hBN covered Pd(111) thin films was investigated using in situ variable-temperature STM. STM images were acquired from bare Pd(111) and hBN covered Pd(111) at temperatures between 600 K and 1000 K. It was found that the hBN overlayer enhances the stability of the underlying Pd surface by suppressing the surface mobility of adatoms. These results provide new, direct insights into the behavior of substrate supported 2D materials at elevated temperatures. Finally, in situ VT-STM was used to investigate the growth of graphene using benzene (C6H6) on Pd(111). STM images were acquired during and after benzene deposition at temperatures between 300 K and 1100 K. Compared to growth of graphene on Pd(111) using other hydrocarbon precursors (e.g. ethylene), benzene enables the growth of graphene at lower T, and at significantly lower doses, likely due to an increased probability of forming C6 and/or C6Hx(x
Book Synopsis Optical Spectroscopy of Two Dimensional Graphene and Boron Nitride by : Long Ju
Download or read book Optical Spectroscopy of Two Dimensional Graphene and Boron Nitride written by Long Ju and published by . This book was released on 2015 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes the use of optical spectroscopy in studying the physical properties of two dimensional nano materials like graphene and hexagonal boron nitride. Compared to bulk materials, atomically thin two dimensional materials have a unique character that is the strong dependence of physical properties on external control. Both electronic band structure and chemical potential can be tuned in situ by electric field-which is a powerful knob in experiment. Therefore the optical study at atomic thickness scale can greatly benefit from modern micro-fabrication technique and electric control of the material properties. As will be shown in this dissertation, such control of both gemometric and physical properties enables new possibilities of optical spectroscopic measurement as well as opto-electronic studies. Other experimental techniques like electric transport and scanning tunneling microscopy and spectroscopy are also combined with optical spectroscopy to reveal the physics that is beyond the reach of each individual technique. There are three major themes in the dissertation. The first one is focused on the study of plasmon excitation of Dirac electrons in monolayer graphene. Unlike plasmons in ordinary two dimensional electron gas, plasmons of 2D electrons as in graphene obey unusual scaling laws. We fabricate graphene micro-ribbon arrays with photolithography technique and use optical absorption spectroscopy to study its absorption spectrum. The experimental result demonstrates the extraordinarily strong light-plasmon coupling and its novel dependence on both charge doping and geometric dimensions. This work provides a first glance at the fundamental properties of graphene plasmons and forms the basis of an emerging subfield of graphene research and applications such as graphene terahertz metamaterials. The second part describes the opto-electronic response of heterostructures composed of graphene and hexagonal boron nitride. We found that there is a charge transfer process between graphene and BN when the exposure of visible light is introduced. We show this photo-induced doping in graphene resembles the modulation doping technique in traditional semiconductor heterojunctions, where a charge doping is introduced while the high mobility is maintained. This work reveals importance of interactions between stacked 2D materials on the overall properties and demonstrate a repeatable and convenient way of fabricating high quality graphene devices with active control of doping patterning. Along this direction, we did further STM experiment to visualize and manipulate charged defects in boron nitride with the help of graphene. The last theme is about the interesting properties of bilayer graphene, which is to some extent more interesting than monolayer graphene due to its electric-eld dependent band structures. Firstly, we visualized the stacking boundary within exfoliated bilayer graphene by near field infrared microscopy. In dual-gated field-effect-transistor devices fabricated on the boundaries, we demonstrated the existence of topologically protected one dimensional conducting channels at the boundary through electric transport measurement. The 1D boundary states also demonstrated the first graphene-based valleytronic device. The topics we are going to talk about in this thesis are quite diversified. Just like the versatile nature of optical spectroscopy, we never limit ourself to a specific technique and do incremental things. Most of the experiments are driven by the important and interesting problems in the two dimensional materials field and we chose the right tool and conceive the right experiment to answer that question. Both pure optical methods and combinations with electric transport and STM measurements were used. I believe the flexibility of optical spectroscopy and its compatibility with other experimental techniques provide a powerful toolbox to explore many possibilities beyond the reach of a single experimental approach. And such a way of doing experiments is very much enjoyable for me.
Book Synopsis Chemical Vapour Deposition Growth of Graphene and Hexagonal Boron Nitride, and a Study of the Electronic and Corrosion Inhibiting Properties of Hexagonal Boron Nitride by : Farzaneh Mahvash Mohammadi
Download or read book Chemical Vapour Deposition Growth of Graphene and Hexagonal Boron Nitride, and a Study of the Electronic and Corrosion Inhibiting Properties of Hexagonal Boron Nitride written by Farzaneh Mahvash Mohammadi and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "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." --
Book Synopsis Synthesis of Bilayer Graphene and Hexagonal Boron Nitride by Chemical Vapor Deposition Method by : Wenjing Fang (Ph. D.)
Download or read book Synthesis of Bilayer Graphene and Hexagonal Boron Nitride by Chemical Vapor Deposition Method written by Wenjing Fang (Ph. D.) and published by . This book was released on 2016 with total page 165 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Synthesis and Characterization of Hexagonal Boron Nitride for Integration with Graphene Electronics by : Michael S. Bresnehan
Download or read book Synthesis and Characterization of Hexagonal Boron Nitride for Integration with Graphene Electronics written by Michael S. Bresnehan and published by . This book was released on 2013 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Growth of Atomic Hexagonal Boron Nitride Layers and Graphene/hexagonal Boron Nitride Heterostructures by Molecular Beam Epitaxy by : Zhongguang Xu
Download or read book Growth of Atomic Hexagonal Boron Nitride Layers and Graphene/hexagonal Boron Nitride Heterostructures by Molecular Beam Epitaxy written by Zhongguang Xu and published by . This book was released on 2016 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: Following with the lateral growth of graphene on in situ epitaxial h-BN flakes by plasma-assisted MBE is discussed in Chapter 4. Single-crystal h-BN domains were grown on Co film substrates at a substrate temperature of 850~900 oC using plasma-assisted MBE. Three-point star shape h-BN domains were observed by SEM, and confirmed by Raman and XPS. The h-BN on Co template was used for in situ growth of multilayer graphene, leading to an h-BN/graphene heterostructure. Carbon atoms preferentially nucleate on Co substrate and edges of h-BN and then grow laterally to form continuous graphene. Further introduction of carbon atoms results in layer-by-layer growth of graphene on graphene and lateral growth of graphene on h-BN until it may cover entire h-BN flakes.
Book Synopsis Structure, Mechanics and Synthesis of Nanoscale Carbon and Boron Nitride by : Michael Rousseas
Download or read book Structure, Mechanics and Synthesis of Nanoscale Carbon and Boron Nitride written by Michael Rousseas and published by . This book was released on 2013 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is divided into two parts. In Part I, we examine the properties of thin sheets of carbon and boron nitride. We begin with an introduction to the theory of elastic sheets, where the stretching and bending modes are considered in detail. The coupling between stretching and bending modes is thought to play a crucial role in the thermodynamic stability of atomically-thin 2D sheets such as graphene. In Chapter 2, we begin by looking at the fabrication of suspended, atomically thin sheets of graphene. We then study their mechanical resonances which are read via an optical transduction technique. The frequency of the resonators was found to depend on their temperature, as was their quality factor. We conclude by offering some interpretations of the data in terms of the stretching and bending modes of graphene. In Chapter 3, we look briefly at the fabrication of thin sheets of carbon and boron nitride nanotubes. We examine the structure of the sheets using transmission and scanning electron microscopy (TEM and SEM, respectively). We then show a technique by which one can make sheets suspended over a trench with adjustable supports. Finally, DC measurements of the resistivity of the sheets in the temperature range 600 - 1400 C are presented. In Chapter 4, we study the folding of few-layer graphene oxide, graphene and boron nitride into 3D aerogel monoliths. The properties of graphene oxide are first considered, after which the structure of graphene and boron nitride aerogels is examined using TEM and SEM. Some models for their structure are proposed. In Part II, we look at synthesis techniques for boron nitride (BN). In Chapter 5, we study the conversion of carbon structures of boron nitride via the application of carbothermal reduction of boron oxide followed by nitridation. We apply the conversion to a wide variety of morphologies, including aerogels, carbon fibers and nanotubes, and highly oriented pyrolytic graphite. In the latter chapters, we look at the formation of boron nitride nanotubes (BNNTs). In Chapter 6, we look at various methods of producing BNNTs from boron droplets, and introduce a new method involving injection of boron powder into an induction furnace. In Chapter 7 we consider another useful process, where ammonia is reacted with boron vapor generated in situ, either through the reaction of boron with metal oxides or through the decomposition of metal borides.
Book Synopsis Molecular Precursors for Graphene Formation Investigated by Scanning Tunneling Microscopy by : Bo Chen
Download or read book Molecular Precursors for Graphene Formation Investigated by Scanning Tunneling Microscopy written by Bo Chen and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Carbon Based Magnetism by : Tatiana Makarova
Download or read book Carbon Based Magnetism written by Tatiana Makarova and published by Elsevier. This book was released on 2006-01-16 with total page 577 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon Based Magnetism is the most complete, detailed, and accurate guide on the magnetism of carbon, the main element of living creatures. Written by the leading experts in the field, the book provides a comprehensive review of relevant experimental data and theoretical concepts related to the magnetism of metal-free carbon systems. These systems include carbon based compounds, namely organic radical magnetic systems, and magnetic materials based on carbon structures. The aim is to advance the understanding of the fundamental properties of carbon. This volume discusses all major modern hypotheses on the physical nature of magnetic ordering in carbon systems. The first chapters deal with magnetic ordering mechanisms in p-electron systems as well as molecular magnets with spins residing only in p-orbitals. The following chapters explore the magnetic properties of pure carbon, with particular emphasis on nanosized carbon systems with closed boundary (fullerenes and nanotubes) and with open boundary (structures with edge-localized magnetic states). The remaining chapters focus on newer topics: experimental observation and theoretical models for magnetic ordering above room temperature in pure carbon. The book also includes twenty three review articles that summarize the most significant recent and ongoing exciting scientific developments and provide the explanation. It also highlights some problems that have yet to be solved and points out new avenues for research. This book will appeal to physicists, chemists and biologists. The most complete, detailed, and accurate Guide in the magnetism of carbon Dynamically written by the leading experts Deals with recent scientific highlights Gathers together chemists and physicists, theoreticians and experimentalists Unified treatment rather than a series of individually authored papers Description of genuine organic molecular ferromagnets Unique description of new carbon materials with Curie temperatures well above ambient.
Book Synopsis Experimental Investigation of Thermal Transport in Graphene and Hexagonal Boron Nitride by : Insun Jo
Download or read book Experimental Investigation of Thermal Transport in Graphene and Hexagonal Boron Nitride written by Insun Jo and published by . This book was released on 2012 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-dimensional graphene, a single layer of graphite, has emerged as an excellent candidate for future electronic material due to its unique electronic structure and remarkably high carrier mobility. Even higher carrier mobility has been demonstrated in graphene devices using hexagonal boron nitride as an underlying dielectric support instead of silicon oxide. Interestingly, both graphene and boron nitride exhibit superior thermal properties, therefore may potentially offer a solution to the increasingly severe heat dissipation problem in nanoelectronics caused by increased power density. In this thesis, we focus on the investigation of the thermal properties of graphene and hexagonal boron nitride. First, scanning thermal microscopy based on a sub-micrometer thermocouple at the apex of a microfabricated tip was employed to image the temperature profiles in electrically biased graphene devices with ~ 100 nm scale spatial resolution. Non-uniform temperature distribution in the devices was observed, and the "hot spot" locations were correlated with the charge concentrations in the channel, which could be controlled by both gate and drain-source biases. Hybrid contact and lift mode scanning has enabled us to obtain the quantitative temperature profiles, which were compared with the profiles obtained from Raman-based thermometry. The temperature rise in the channel provided an important insight into the heat dissipation mechanism in Joule-heated graphene devices. Next, thermal conductivity of suspended single and few-layer graphene was measured using a micro-bridge device with built-in resistance thermometers. Polymer-assisted transfer technique was developed to suspend graphene layers on the pre-fabricated device. The room temperature thermal conductivity values of 1-7 layer graphene were measured to be lower than that of bulk graphite, and the value appeared to increase with increasing sample thickness. These observations can be explained by the impact of the phonon scattering by polymer residue remaining on the sample surfaces. Lastly, thermal conductivity of few-layer hexagonal boron nitride sample was measured by using the same device and technique used for suspended graphene. Measurements on samples with different suspended lengths but similar thickness allowed us to extract the intrinsic thermal conductivity of the samples as well as the contribution of contact thermal resistance to the overall thermal measurement. The room temperature thermal conductivity of 11 layer sample approaches the basal-plane value reported in the bulk sample. Lower thermal conductivity was measured in a 5 layer sample than an 11 layer sample, which again supports the polymer effect on the thermal transport in few-layer hexagonal boron nitride.
Book Synopsis Graphene and Hexagonal Boron Nitride on Transition Metals and Their Application by : Thomas Brugger
Download or read book Graphene and Hexagonal Boron Nitride on Transition Metals and Their Application written by Thomas Brugger and published by . This book was released on 2010 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Microscopy and Spectroscopy of Graphene by : Recep Zan
Download or read book Microscopy and Spectroscopy of Graphene written by Recep Zan and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Since its discovery, the one atom thick material graphene has been at the centre of growing interest in two-dimensional materials. Due to its exceptional properties, graphene is a rich topic to explore by physicists, chemists, engineers and materials scientists. In addition to its use in the fundamental research, graphene is also a promising candidate for future electronics, photonics and energy storage devices. The project presented in this thesis was carried out to explore the structure of suspended graphene in particular in order to probe the metal-graphene interaction via Transmission Electron Microscopy, as most graphene applications require interfacing with metals. As the work was based on free standing graphene, graphene layers obtained by mechanical cleavage or growth on a substrate were transferred onto TEM-grids. Therefore, fabrication, suspended sample preparation and identification of graphene layers were first discussed for a better understanding of how to obtain high quality graphene, as this was essential for the rest of the project. Structural, topographic and chemical analysis of pristine suspended graphene layers were investigated in detail via Transmission Electron Microscopy and Scanning Tunnelling Microscopy. The latter technique was also employed for graphene on a substrate along with establishing annealing conditions for residue free graphene. Metal deposited suspended graphene layers were then investigated in the electron microscopes. Different metal behaviours were observed on the graphene surfaces for the same amount of metal evaporation. Generally, metals interact only weakly with graphene as they are not observed on clean (residue free) parts and are mainly clustered. On the other hand, graphene etching has been observed in the presence of metals. The etching was initiated with graphene vacancy formation as a result of the interaction between metal and carbon atoms on clean graphene. Once a vacancy was created, a hole quickly formed and eventually the graphene layers were destroyed. However, those holes created by metals were healed spontaneously either by non-hexagonal or perfect hexagonal rings. The possible etching and healing mechanisms of the suspended graphene were also discussed.
Book Synopsis Graphene and Hexagonal Boron Nitride Heterostructures for Beyond CMOS Applications by : Sangwoo Kang
Download or read book Graphene and Hexagonal Boron Nitride Heterostructures for Beyond CMOS Applications written by Sangwoo Kang and published by . This book was released on 2016 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: Scaling limits of conventional complementary metal oxide semiconductor (CMOS) technology has motivated the research of numerous beyond CMOS device concepts. One such device is the interlayer tunnel FET (ITFET). This device is demonstrated using the two-dimensional (2D) materials bilayer graphene and hexagonal boron nitride (hBN). Stacking these materials together, we fabricate a double bilayer graphene and hBN heterostructure where the two graphene layers function as the top and bottom electrodes and the hBN as the tunnel barrier of the ITFET. Significant negative differential resistance (NDR) in the interlayer current-voltage characteristic is demonstrated at room temperature. Electrostatic analysis reveals that the multiple NDR peaks are due to energetic band alignment between the two sub-bands of the top and bottom bilayer graphene at the K-point of the Brillouin zone. Temperature dependent and parallel magnetic field measurements are conducted to further confirm that the conduction mechanism is momentum and energy conserving resonant tunneling. In addition, we demonstrate how the NDR can be used for implementing a one-transistor static random access memory element. Improvements in the transfer method which allowed rotationally aligned top and bottom electrode layers, made possible extensive experimental studies of 2D heterostructure based ITFETs. Utilizing such technique, we conducted experiments involving thicker multilayer graphene. We analyze how the graphene thickness and stacking order can influence the resonance condition and how this affects the overall device characteristic. The effects of interlayer hBN scaling such as increased tunneling current and peak position shifting is also briefly dealt with. Current-voltage simulations based on Bardeen transfer Hamiltonian approach were conducted for these devices, and it is shown that the peak positions predicted by theory match well with those obtained through measurements.
Book Synopsis Topological Insulator and Related Topics by :
Download or read book Topological Insulator and Related Topics written by and published by Academic Press. This book was released on 2021-09-24 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological Insulator and Related Topics, Volume 108 in the Semiconductors and Semimental series, highlights new advances in the field, with this new volume presenting interesting chapters on topics such as Majorana modes at the ends of one dimensional topological superconductors, Optical/electronic properties of Weyl semimetals, High magnetic fields to unveil the electronic structure, magnetic field-induced transitions, and unconventional transport properties of topological semimetals, New aspects of strongly correlated superconductivity in the nearly flat-band regime, Anomalous transport properties in topological semimetals, Pseudo-gauge field and piezo-electromagnetic response in topological materials, Topological Gapped States Protected by Spatial Symmetries, and more. Provides the authority and expertise of leading contributors from an international board of authors Presents the latest release in the Semiconductors and Semimetals series Updated release includes the latest information on Topological Insulator and Related Topics
Book Synopsis The Thermal Effect of Hexagonal Boron Nitride Supports in Graphene Devices by : David Seiji Kar Liang Choi
Download or read book The Thermal Effect of Hexagonal Boron Nitride Supports in Graphene Devices written by David Seiji Kar Liang Choi and published by . This book was released on 2018 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt: A fundamental understanding of thermal dissipation and energy transport is necessary for designing robust electronic systems and energy conversion devices. In many of these systems, minimizing the operating temperature of the working components is required for increasing the performance, lifetime, efficiency, and reliability of the device. For example, hot spots in transistors caused by the conversion of electronic energy to thermal energy has become a bottleneck in the continued scaling of microelectronics. As the demand for compact, highly conformable and mobile electronics continues to push the limit of miniaturization, these phenomena increasingly occur at the nanoscale. At these length scales, the governing physical principles differ from classical laws based on continuum mechanics and instead require a quantum mechanical treatment. The thermal transport properties of traditional three-dimensional (3D) heat conducting materials such as the metal interconnects in nanoelectronic devices tend to degrade as the critical dimension is reduced. In contrast, the thermal properties of a new class of van der Waals-based two-dimensional (2D) materials can show different size confinement effects that can potentially be utilized for thermal management. First realized by the isolation of graphene, these materials have become attractive candidates for future-generation electronic and thermal components. Due to their atomic thinness, the properties of 2-D materials are highly sensitive to their operating environment. The studies in this dissertation therefore aim to answer critical questions surrounding the practical applicability of graphene and its dielectric isomorph hexagonal boron nitride as thermal materials in real devices. Specifically, the fundamental heat dissipation pathways of joule-heated graphene channels are inspected within the framework of silicon-based electronics as well as next-generation flexible electronic architectures. The study reveals that lateral heat spreading is essential to mitigating hot-spot formation. As a result, the inclusion of h-BN as a thermal interface material between the active graphene layer and the underlying support facilitates significant reductions in device operating temperatures due to enhanced lateral heat spreading. More than a passive thermal layer, an h-BN support increases the intrinsic thermal conductivity of graphene relative to other support materials based on an additional study in this work. An analytical solution of the phonon Boltzmann transport equation is derived to explain the observed phenomenon
