Scattering Theory of Graphene Grain Boundaries

The implementation of graphene-based electronics requires fabrication processes that are able to cover large device areas, since the exfoliation method is not compatible with industrial applications. The chemical vapor deposition of large-area graphene represents a suitable solution; however, it has an important drawback of producing polycrystalline graphene with the formation of grain boundaries, which are responsible for the limitation of the device’s performance. With these motivations, we formulate a theoretical model of a single-layer graphene grain boundary by generalizing the graphene Dirac Hamiltonian model. The model only includes the long-wavelength regime of the charge carrier transport, which provides the main contribution to the device conductance. Using symmetry-based arguments deduced from the current conservation law, we derive unconventional boundary conditions characterizing the grain boundary physics and analyze their implications on the transport properties of the system. Angle resolved quantities, such as the transmission probability, are studied within the scattering matrix approach. The conditions for the existence of preferential transmission directions are studied in relation with the grain boundary properties. The proposed theory provides a phenomenological model to study grain boundary physics within the scattering approach, and represents per se an important enrichment of the scattering theory of polycrystalline graphene. Moreover, the outcomes of the theory can contribute to understanding and limiting the detrimental effects of graphene grain boundaries, while also providing a benchmark for more elaborate techniques.

Download Full-text

Scattering Theory of Graphene Grain Boundaries

10.20944/preprints201808.0167.v1 ◽

2018 ◽

Author(s):

Francesco Romeo ◽

Antonio Di Bartolomeo

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Scattering Theory ◽

Chemical Vapor ◽

Transmission Probability ◽

Industrial Applications ◽

Large Area ◽

Current Conservation ◽

Long Wavelength ◽

Boundary Properties

The implementation of graphene-based electronics requires fabrication processes able to cover large device areas since exfoliation method is not compatible with industrial applications. Chemical vapor deposition of large-area graphene represents a suitable solution having the important drawback of producing polycrystalline graphene with formation of grain boundaries, which are responsible for limitation of the device performance. With these motivations, we formulate a theoretical model of graphene grain boundary by generalizing the graphene Dirac Hamiltonian model. The model only includes the long-wavelength regime of the particle transport, which provides the main contribution to the device conductance. Using symmetry-based arguments deduced from the current conservation law, we derive unconventional boundary conditions characterizing the grain boundary physics and analyze their implications on the transport properties of the system. Angle resolved quantities, such as the transmission probability, are studied within the scattering matrix approach. The conditions for the existence of preferential transmission directions are studied in relation with the grain boundary properties. The proposed theory provides a phenomenological model to study grain boundary physics within the scattering approach and represents per se an important enrichment of the scattering theory of graphene. Moreover, the outcomes of the theory can contribute in understanding and limiting detrimental effects of graphene grain boundaries also providing a benchmark for more elaborated techniques.

Download Full-text

Grain Boundary and Misorientation Angle Dependent Thermal Transport in Single-layer MoS2

Nanoscale ◽

10.1039/d1nr05113j ◽

2022 ◽

Author(s):

Ke Xu ◽

Ting Liang ◽

Zhisen Zhang ◽

Xuezheng Cao ◽

Meng Han ◽

...

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Misorientation Angle ◽

Thermal Transport ◽

Single Layer ◽

Large Area ◽

Grain Misorientation

Grain boundaries (GBs) are inevitable defects in large-area MoS2 samples but play a key role in their properties, however, the influence of grain misorientation on thermal transport remains largely unknown...

Download Full-text

Effect of a Balanced Concentration of Hydrogen on Graphene CVD Growth

Journal of Nanomaterials ◽

10.1155/2016/9640935 ◽

2016 ◽

Vol 2016 ◽

pp. 1-10 ◽

Cited By ~ 14

Author(s):

S. Chaitoglou ◽

E. Pascual ◽

E. Bertran ◽

J. L. Andujar

Keyword(s):

Copper Substrate ◽

Single Layer ◽

Chemical Vapor ◽

Experimental System ◽

Single Layer Graphene ◽

Growth Time ◽

Monolayer Graphene ◽

Flow Ratio ◽

Large Area ◽

Hydrogen Flow

The extraordinary properties of graphene make it one of the most interesting materials for future applications. Chemical vapor deposition (CVD) is the synthetic method that permits obtaining large areas of monolayer graphene. To achieve this, it is important to find the appropriate conditions for each experimental system. In our CVD reactor working at low pressure, important factors appear to be the pretreatment of the copper substrate, considering both its cleaning and its annealing before the growing process. The carbon precursor/hydrogen flow ratio and its modification during the growth are significant in order to obtain large area graphene crystals with few defects. In this work, we have focused on the study of the methane and the hydrogen flows to control the production of single layer graphene (SLG) and its growth time. In particular, we observe that hydrogen concentration increases during a usual growing process (keeping stable the methane/hydrogen flow ratio) resulting in etched domains. In order to balance this increase, a modification of the hydrogen flow results in the growth of smooth hexagonal SLG domains. This is a result of the etching effect that hydrogen performs on the growing graphene. It is essential, therefore, to study the moderated presence of hydrogen.

Download Full-text

The effect of growth parameters on the intrinsic properties of large-area single layer graphene grown by chemical vapor deposition on Cu

Carbon ◽

10.1016/j.carbon.2011.07.063 ◽

2012 ◽

Vol 50 (1) ◽

pp. 134-141 ◽

Cited By ~ 65

Author(s):

Murari Regmi ◽

Matthew F. Chisholm ◽

Gyula Eres

Keyword(s):

Chemical Vapor Deposition ◽

Vapor Deposition ◽

Growth Parameters ◽

Single Layer ◽

Chemical Vapor ◽

Single Layer Graphene ◽

Intrinsic Properties ◽

Large Area ◽

Layer Graphene

Download Full-text

Improving contact performance of graphene on p-type GaN thin films with V-pits microstructures

International Journal of Modern Physics B ◽

10.1142/s0217979218400520 ◽

2018 ◽

Vol 32 (19) ◽

pp. 1840052

Author(s):

Ruo-Nong Song ◽

Wen-Cheng Ke

Keyword(s):

Thin Films ◽

Ohmic Contact ◽

Carrier Transport ◽

Single Layer ◽

Chemical Vapor ◽

Single Layer Graphene ◽

Visible Range ◽

Organic Chemical ◽

Metal Organic ◽

P Type

This study presents the electrical properties of graphene that directly is contact on two types of p-type GaN thin films. The diameter of several hundred nanometer V-pits were formed on the p-GaN thin films by adjusting the NH3 flow rate during the metal organic chemical vapor deposition epitaxial process. The single-layer graphene with a high transmittance of 97% in the visible range was transferred on p-GaN thin films to form an Ohmic contact. The V-pits provide more carrier transport paths that promote the carrier tunneling into p-GaN thin films, resulting in a better Ohmic contact performance. In addition, the increased current value was attributed to the presence of V-pits on the p-GaN thin films.

Download Full-text

Improved Mobility and Bias Stability of Thin Film Transistors Using the Double-Layer a-InGaZnO/a-InGaZnO:N Channel

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2016.12340 ◽

2016 ◽

Vol 16 (4) ◽

pp. 3659-3663

Author(s):

H Yu ◽

L Zhang ◽

X. H Li ◽

H. Y Xu ◽

Y. C Liu

Keyword(s):

Thin Film ◽

Double Layer ◽

Thin Film Transistors ◽

Carrier Transport ◽

Single Layer ◽

Channel Structure ◽

Gate Insulator ◽

Large Area ◽

Threshold Voltage Shift ◽

High Carrier

The amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) were demonstrated based on a double-layer channel structure, where the channel is composed of an ultrathin nitrogenated a-IGZO (a-IGZO:N) layer and an undoped a-IGZO layer. The double-layer channel device showed higher saturation mobility and lower threshold-voltage shift (5.74 cm2/Vs, 2.6 V) compared to its single-layer counterpart (0.17 cm2/Vs, 7.23 V). The improvement can be attributed to three aspects: (1) improved carrier transport properties of the channel by the a-IGZO:N layer with high carrier mobility and the a-IGZO layer with high carrier concentration, (2) reduced interfacial trap density between the active channel and the gate insulator, and (3) higher surface flatness of the double-layer channel. Our study reveals key insights into double-layer channel, involving selecting more suitable electrical property for back-channel layer and more suitable interface modification for active layer. Meanwhile, room temperature fabrication amorphous TFTs offer certain advantages on better flexibility and higher uniformity over a large area.

Download Full-text

Correction: Direct chemical vapor deposition synthesis of large area single-layer brominated graphene

RSC Advances ◽

10.1039/c9ra90038a ◽

2019 ◽

Vol 9 (28) ◽

pp. 16057-16057

Author(s):

Maria Hasan ◽

Wang Meiou ◽

Liu Yulian ◽

Sami Ullah ◽

Huy Q. Ta ◽

...

Keyword(s):

Chemical Vapor Deposition ◽

Vapor Deposition ◽

Single Layer ◽

Chemical Vapor ◽

Large Area

Correction for ‘Direct chemical vapor deposition synthesis of large area single-layer brominated graphene’ by Maria Hasan et al., RSC Adv., 2019, 9, 13527–13532.

Download Full-text