scholarly journals FIELD DESORPTION MICROSCOPY OF CARBON-COATED FIELD ELECTRON EMITTERS

2021 ◽  
pp. 25-31
Author(s):  
Дмитрий Петрович Бернацкий ◽  
Виктор Георгиевич Павлов
Keyword(s):  
Carbon Nanostructures ◽  
Carbon Film ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Multilayer Graphene ◽  
Field Desorption ◽  
Continuous Mode ◽  
Mode Field ◽  
Field Electron ◽  
Electron Emitters

Полевые электронные эмиттеры в форме металлического острия с пленкой углерода на поверхности обладают рядом перспективных эксплуатационных свойств. Характеристики эмиттера зависят от фазового состава, толщины и однородности пленки. Определение параметров пленок толщиной в один или несколько моноатомных слоев представляет определённые трудности. В данной работе образование и характеристики углеродных наноструктур на поверхности полевых эмиттеров из иридия и рения исследуются с помощью полевой десорбционной микроскопии непрерывного режима. На полевых десорбционных изображениях области углеродных наноструктур проявляются в виде локальных вспышек (лавинообразная десорбция). При покадровом анализе видеозаписей вспышек обнаружено несколько стадий формирования вспышек и выявлены различия в протекании десорбции с углеродных наноструктур на иридии и на рении. Обнаруженные различия объясняются образованием на иридии однослойного, а на рении многослойного графена. Десорбционные изображения выявляют неоднородности и локальные различия толщины пленки. Показано, что полевая десорбционная микроскопия непрерывного режима позволяет определять закономерности формирования полевых десорбционных изображений различных углеродных наноструктур, в частности, однослойного и многослойного графена на поверхности полевого эмиттера, и проводить диагностику поверхности после науглероживания и контролировать однородность получаемого покрытия. Получаемые данные полезны для разработки технологии эффективных полевых электронных эмиттеров. Field electron emitters in the form of a metal tip with a carbon film on the surface have a number of promising operational properties. The characteristics of the emitter depend on the phase composition, thickness and uniformity of the film. Determining the parameters of films with a thickness of one or more monoatomic layers presents certain difficulties. In this paper, the formation and characteristics of carbon nanostructures on the surface of field emitters made of iridium and rhenium are studied using continuous-mode field desorption microscopy. In the field desorption images, the regions of carbon nanostructures appear as local flashes (avalanche-like desorption). Frame-by-frame analysis of flash video recordings revealed several stages of the flash formation and revealed differences in the desorption from carbon nanostructures on iridium and rhenium. The found differences are explained by formation of the single-layer graphene on iridium and a multilayer graphene on rhenium. Desorption images reveal inhomogeneities and local differences in the film thickness. It is shown that continuous-mode field desorption microscopy makes it possible to determine the regularities of formation of the field desorption images of various carbon nanostructures, in particular, the single-layer and multilayer graphene on the surface of the field emitter, and to diagnose the surface after carburization. Besides, control the uniformity of the resulting coating is possible. The obtained data are useful for developing technology of the effective field electronic emitters.

Graphene Production With Stirred Media Mills

2010 ◽  
Vol 1259 ◽  
Author(s):  
Catharina Knieke ◽  
Angela Berger ◽  
Wolfgang Peukert
Keyword(s):  
Large Scale ◽  
Chemical Properties ◽  
Single Layer ◽  
Single Layer Graphene ◽  
High Yield ◽  
Graphene Sheets ◽  
Multilayer Graphene ◽  
Scale Production ◽  
Graphite Particles ◽  
Media Milling

AbstractSince the discovery of stable graphene sheets by Novoselov und Geim in 2004 the one atom thick carbon material has been attracted great interest because of its outstanding physical, mechanical and chemical properties. Although there had been intensive research to find new ways in the preparation of single-layer graphene sheets in the last few years, especially the large-scale production of graphene still remains challenging. In this paper we present a new approach, which allows the high-yield production of graphene sheets in a simple stirred media milling process. Under mild milling conditions single- and multilayer graphene sheets have been successfully produced from commercial graphite powder in a liquid medium. During the delamination procedure, the graphite particles were stressed between the milling beads. Shear and compressive normal forces can lead under mild milling conditions, i.e. low stress energies, to a continuous mechanical peeling of graphene sheets from the graphite surface. By means of Atomic Force Microscopy a high yield of single- and multilayer graphene sheets was detected. A concentration of exfoliated sheets of 2 wt% starting from a 5 wt% suspension of coarse graphite particles could be determined after a milling time of only 3 h. This concentration is much higher than those, which were reached by most of the known chemical methods. Since stirred media milling can be realized as large-scale process, a high-yield and low-cost production of graphene flakes becomes possible at ambient temperature.

scholarly journals Tight-Binding Investigation of Structural and Vibrational Properties of Graphene-Single Wall Carbon Nanotube Junctions

2020 ◽  
Author(s):  
Juhi Srivastava ◽  
Anshu Gaur
Keyword(s):  
Charge Transfer ◽  
Carbon Nanostructures ◽  
Tight Binding ◽  
Single Layer ◽  
Hybrid Nanostructures ◽  
Structural Deformation ◽  
Single Layer Graphene ◽  
Vibrational Properties ◽  
Carbon Nanotube Junctions ◽  
Hybrid Devices

Hybrid carbon nanostructures based on single walled carbon nanotubes (SWNT) and single layer graphene (SLG) are drawing much attention lately for their applications in a range of efficient hybrid devices. Few recent studies, addressing the interaction behavior at the heterojunction, consider charge transfer between the constituents (SWNT and SLG) to be responsible for changes in the electronic and vibrational properties in their hybrid system. We report the effect of various factors, arising due to the interactions between atoms of SWNT and SLG, on the structural and vibrational roperties of hybrid nanostructures investigated computationally within the framework of tight-binding DFT. These factors such as the van der Waal’s (vdW) forces, structural deformation and the charge transfer, are seen to affect the Raman active phonon frequencies of SWNT and SLG in the hybrid nanostructure. These factors are already known to affect the vibrational properties on SWNT and SLG separately and in this work, we have explored their role and interplay between these factors in hybrid systems. The contribution of different factors to the total shift observed in phonon frequencies are estimated and it is perceived from our findings that not only the charge transfer but the structural deformations and the vdW forces also affect the vibrational properties of components within the hybrid, with structural deformation being the leading factor. With decreasing separation between SWNT and SLG, the charge transfer and the vdW forces, both increase. However, the increase in vdW forces is relatively much higher and likely to be the main cause for larger Raman shifts observed at smaller separations.

scholarly journals Printing of Crumpled CVD Graphene via Blister-Based Laser-Induced Forward Transfer

Nanomaterials ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 1103 ◽  
Author(s):  
Maxim S. Komlenok ◽  
Pavel A. Pivovarov ◽  
Margarita A. Dezhkina ◽  
Maxim G. Rybin ◽  
Sergey S. Savin ◽  
...  
Keyword(s):  
Carbon Film ◽  
Graphene Film ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Original Structure ◽  
Si Substrate ◽  
Layer Graphene ◽  
Forward Transfer ◽  
Laser Techniques ◽  
Original Crystal

The patterning and transfer of a two-dimensional graphene film without damaging its original structure is an urgent and difficult task. For this purpose, we propose the use of the blister-based laser-induced forward transfer (BB-LIFT), which has proven itself in the transfer of such delicate materials. The ease of implementation of laser techniques reduces the number of intermediate manipulations with a graphene film, increasing its safety. The work demonstrates the promise of BB-LIFT of single-layer graphene from a metal surface to a SiO2/Si substrate. The effect of the parameters of this method on the structure of transferred graphene islands is investigated. The relevance of reducing the distance between irradiating and receiving substrates for the transfer of free-lying graphene is demonstrated. The reasons for the damage to the integrity of the carbon film observed in the experiments are discussed. The preservation of the original crystal structure of transferred graphene is confirmed by Raman spectroscopy.

scholarly journals Epitaxial Growth of Uniform Single-Layer and Bilayer Graphene with Assistance of Nitrogen Plasma

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3217
Author(s):  
Shaoen Jin ◽  
Junyu Zong ◽  
Wang Chen ◽  
Qichao Tian ◽  
Xiaodong Qiu ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Large Scale ◽  
Single Layer ◽  
Bilayer Graphene ◽  
Nitrogen Plasma ◽  
Single Layer Graphene ◽  
Scanning Tunneling ◽  
Multilayer Graphene ◽  
Two Dimensional ◽  
Graphene Films

Graphene was reported as the first-discovered two-dimensional material, and the thermal decomposition of SiC is a feasible route to prepare graphene films. However, it is difficult to obtain a uniform single-layer graphene avoiding the coexistence of multilayer graphene islands or bare substrate holes, which give rise to the degradation of device performance and becomes an obstacle for the further applications. Here, with the assistance of nitrogen plasma, we successfully obtained high-quality single-layer and bilayer graphene with large-scale and uniform surface via annealing 4H-SiC(0001) wafers. The highly flat surface and ordered terraces of the samples were characterized using in situ scanning tunneling microscopy. The Dirac bands in single-layer and bilayer graphene were measured using angle-resolved photoemission spectroscopy. X-ray photoelectron spectroscopy combined with Raman spectroscopy were used to determine the composition of the samples and to ensure no intercalation or chemical reaction of nitrogen with graphene. Our work has provided an efficient way to obtain the uniform single-layer and bilayer graphene films grown on a semiconductive substrate, which would be an ideal platform for fabricating two-dimensional devices based on graphene.

scholarly journals Tight-Binding Investigation of Structural and Vibrational Properties of Graphene-Single Wall Carbon Nanotube Junctions

2020 ◽  
Author(s):  
Juhi Srivastava ◽  
Anshu Gaur
Keyword(s):  
Charge Transfer ◽  
Carbon Nanostructures ◽  
Tight Binding ◽  
Single Layer ◽  
Hybrid Nanostructures ◽  
Structural Deformation ◽  
Single Layer Graphene ◽  
Vibrational Properties ◽  
Carbon Nanotube Junctions ◽  
Hybrid Devices

Hybrid carbon nanostructures based on single walled carbon nanotubes (SWNT) and single layer graphene (SLG) are drawing much attention lately for their applications in a range of efficient hybrid devices. Few recent studies, addressing the interaction behavior at the heterojunction, consider charge transfer between the constituents (SWNT and SLG) to be responsible for changes in the electronic and vibrational properties in their hybrid system. We report the effect of various factors, arising due to the interactions between atoms of SWNT and SLG, on the structural and vibrational roperties of hybrid nanostructures investigated computationally within the framework of tight-binding DFT. These factors such as the van der Waal’s (vdW) forces, structural deformation and the charge transfer, are seen to affect the Raman active phonon frequencies of SWNT and SLG in the hybrid nanostructure. These factors are already known to affect the vibrational properties on SWNT and SLG separately and in this work, we have explored their role and interplay between these factors in hybrid systems. The contribution of different factors to the total shift observed in phonon frequencies are estimated and it is perceived from our findings that not only the charge transfer but the structural deformations and the vdW forces also affect the vibrational properties of components within the hybrid, with structural deformation being the leading factor. With decreasing separation between SWNT and SLG, the charge transfer and the vdW forces, both increase. However, the increase in vdW forces is relatively much higher and likely to be the main cause for larger Raman shifts observed at smaller separations.

Interactions between C and Cu atoms in single-layer graphene: direct observation and modelling

Nanoscale ◽  
2016 ◽  
Vol 8 (1) ◽  
pp. 529-535 ◽  
Author(s):  
Emi Kano ◽  
Ayako Hashimoto ◽  
Tomoaki Kaneko ◽  
Nobuo Tajima ◽  
Takahisa Ohno ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Direct Observation ◽  
Energy Barrier ◽  
Carbon Nanostructures ◽  
Morphological Changes ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Layer Graphene ◽  
Doped Graphene ◽  
Aberration Corrected

We directly observed unique morphological changes in Cu-doped graphene by aberration-corrected TEM. DFT calculations reveal a reduction of energy barrier that caused rotation of C–C bonds near Cu atoms. Our results suggest that individual Cu atoms can catalyse reconstruction of carbon nanostructures.

Field Electron Emission Characteristics and Physical Mechanism of Individual Single-Layer Graphene

ACS Nano ◽  
2010 ◽  
Vol 4 (11) ◽  
pp. 6332-6336 ◽  
Author(s):  
Zhiming Xiao ◽  
Juncong She ◽  
Shaozhi Deng ◽  
Zikang Tang ◽  
Zhibing Li ◽  
...  
Keyword(s):  
Electron Emission ◽  
Physical Mechanism ◽  
Single Layer ◽  
Field Electron Emission ◽  
Single Layer Graphene ◽  
Emission Characteristics ◽  
Layer Graphene ◽  
Field Electron

scholarly journals Unconventional satellite resistance peaks in moiré superlattice of h-BN/ AB-stacked tetralayer-graphene heterostructures

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Fumiya Mukai ◽  
Kota Horii ◽  
Ryoya Ebisuoka ◽  
Kenji Watanabe ◽  
Takashi Taniguchi ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Fermi Surface ◽  
Energy Gap ◽  
Hexagonal Boron Nitride ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Multilayer Graphene ◽  
Two Dimensional ◽  
Layer Graphene ◽  
Superlattice Structure

AbstractMost studies on moiré superlattices formed from a stack of h-BN (two-dimensional hexagonal boron nitride) and graphene have focused on single layer graphene; graphene with multiple layers is less understood. Here, we show that a moiré superlattice of multilayer graphene shows features arising from the anisotropic Fermi surface affected by the superlattice structure. The moiré superlattice of a h-BN/AB-stacked tetralayer graphene heterostructures exhibited resistivity peaks showing a complicated dependence on the perpendicular electric field. The peaks were not due to secondary Dirac cones forming, but rather opening of the energy gap due to folding of the anisotropic Fermi surface. In addition, superlattice peaks resulted from mixing of light- and heavy-mass bilayer-like bands via the superlattice potential. The gaps did not open on the boundary of the superlattice Brillouin zone, but rather opened inside it, which reflected the anisotropy of the Fermi surface of multilayer graphene.

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