Correlating nucleation density with heating ramp rates in continuous graphene film formation

Jung, Da Hee; Kang, Cheong; Son, Byung Hee; Ahn, Y. H.; Lee, Jin Seok

doi:10.1016/j.carbon.2014.09.016

Cited by 8 publications

(8 citation statements)

References 49 publications

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“…The fabrication began with synthesizing graphene on a copper foil using methane and hydrogen gases, and the synthesized graphene was transferred to a silicon substrate with a 300 nm thick SiO 2 layer. , To establish the graphene layer within the device channel, we used a reactive ion etching (RIE) to pattern the graphene to a size of 100 × 14 μm 2 . The patterned graphene layer was used as an anchor for MoS 2 synthesis in another atmosphere-pressure CVD chamber.…”

Section: Methodsmentioning

confidence: 99%

Evaluation of Transport Parameters in MoS₂/Graphene Junction Devices Fabricated by Chemical Vapor Deposition

Kim

Nguyen

Lee

et al. 2018

ACS Appl. Mater. Interfaces

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We demonstrated imaging of the depletion layer in a MoS/graphene heterojunction fabricated by chemical vapor deposition and obtained their transport parameters such as diffusion length, lifetime, and mobility by using scanning photocurrent microscopy (SPCM). The device exhibited a n-type operation, which was determined by the MoS layer with a lower mobility. The SPCM revealed the presence of the depletion layer at the heterojunction, whereas graphene provided an excellent electrical contact for the MoS layer without resulting in a rectifying behavior, even if they were anchored within a very short range. The polarity of the photocurrent signal switched when we applied a drain-source bias voltage, from which we extracted the potential barrier at the junction. More importantly, a bias-dependent SPCM allowed us to simultaneously record the diffusion lengths of both majority and minority carriers for the respective MoS and graphene layers. By combining the diffusion lengths with the lifetimes measured by femtosecond SPCM, we determined the electron and hole mobilities in each layer, from which we found that the electron mobility (160 cm V s) was higher than the hole mobility (80 cm V s) in MoS, whereas the hole mobility (15 000 cm V s) was relatively higher in graphene.

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Section: Methodsmentioning

confidence: 99%

Evaluation of Transport Parameters in MoS₂/Graphene Junction Devices Fabricated by Chemical Vapor Deposition

Kim

Nguyen

Lee

et al. 2018

ACS Appl. Mater. Interfaces

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“…Since the first demonstration of the growth of graphene by chemical vapor deposition (CVD) on copper, a variety of improvements such as achieving centimeter size single crystals − and high carrier mobility comparable to mechanically exfoliated graphene have been realized . These developments have made CVD growth on copper the most prominent method for graphene production for various suggested applications. − Therefore, the high demand for an economical and reproducible technique for the mass scale production of high quality graphene has led to many studies on CVD growth mechanisms. ,− Li et al demonstrated that due to the very low solubility of carbon in copper, surface-adsorption governs graphene growth and makes it a self-limited process . The growth terminates as soon as the copper surface is fully covered with graphene, since the active surface area on which to catalyze methane decomposition and supply the carbon source is lost.…”

Section: Introductionmentioning

confidence: 99%

Spontaneous Nucleation and Growth of Graphene Flakes on Copper Foil in the Absence of External Carbon Precursor in Chemical Vapor Deposition

Khaksaran

Kaya

2018

ACS Omega

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In this work, we uncover a mechanism initiating spontaneous nucleation of graphene flakes on copper foil during the annealing phase of chemical vapor deposition (CVD) process. We demonstrate that the carbon in the bulk of copper foil is the source of nucleation. Although carbon solubility in a pure copper bulk is very low, excess carbon can be embedded inside the copper foil during the foil production process. Using time-of-flight secondary ion mass spectrometry, we measured the distribution profile of carbon atoms inside the copper foils and its variation by thermal annealing. We also studied the role of hydrogen in the segregation of carbon from the bulk to the surface of copper during annealing by scanning electron microscopy and Raman analysis. We found that carbon atoms diffuse out from the copper foil and accumulate on its surface during annealing in the presence of hydrogen. Consequently, graphene crystals can be nucleated and grown while “any external” carbon precursor was entirely avoided. To our knowledge, this is the first time that such growth has been demonstrated to take place. We believe that this finding brings a new insight into the initial nucleation of graphene in the CVD process and helps to achieve reproducible growth recipes.

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“…In this growth process, graphene is synthesized by thermal decomposition of carbon precursor instead of sublimation of surface Si atoms from SiC substrate. By both using carbon precursor and controlling the dynamic flow in the chamber [ 11 ], various reaction parameters in affecting the number of layers and the defect degree of the synthesized graphene have been reported, such as annealing time, heating ramp rates [ 19 ], hydrogen partial pressure [ 20 ], and growth time [ 21 ]. Among them, EG by CVD process is more versatile than EG by sublimation of Si atoms from SiC surface.…”

Section: Introductionmentioning

confidence: 99%

Effect of Growth Pressure on Epitaxial Graphene Grown on 4H-SiC Substrates by Using Ethene Chemical Vapor Deposition

et al. 2015

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The Si(0001) face and C(000-1) face dependences on growth pressure of epitaxial graphene (EG) grown on 4H-SiC substrates by ethene chemical vapor deposition (CVD) was studied using atomic force microscopy (AFM) and micro-Raman spectroscopy (μ-Raman). AFM revealed that EGs on Si-faced substrates had clear stepped morphologies due to surface step bunching. However, This EG formation did not occur on C-faced substrates. It was shown by μ-Raman that the properties of EG on both polar faces were different. EGs on Si-faced substrates were relatively thinner and more uniform than on C-faced substrates at low growth pressure. On the other hand, D band related defects always appeared in EGs on Si-faced substrates, but they did not appear in EG on C-faced substrate at an appropriate growth pressure. This was due to the μ-Raman covering the step edges when measurements were performed on Si-faced substrates. The results of this study are useful for optimized growth of EG on polar surfaces of SiC substrates.

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Correlating nucleation density with heating ramp rates in continuous graphene film formation

Cited by 8 publications

References 49 publications

Evaluation of Transport Parameters in MoS₂/Graphene Junction Devices Fabricated by Chemical Vapor Deposition

Evaluation of Transport Parameters in MoS₂/Graphene Junction Devices Fabricated by Chemical Vapor Deposition

Spontaneous Nucleation and Growth of Graphene Flakes on Copper Foil in the Absence of External Carbon Precursor in Chemical Vapor Deposition

Effect of Growth Pressure on Epitaxial Graphene Grown on 4H-SiC Substrates by Using Ethene Chemical Vapor Deposition

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Correlating nucleation density with heating ramp rates in continuous graphene film formation

Cited by 8 publications

References 49 publications

Evaluation of Transport Parameters in MoS2/Graphene Junction Devices Fabricated by Chemical Vapor Deposition

Evaluation of Transport Parameters in MoS2/Graphene Junction Devices Fabricated by Chemical Vapor Deposition

Spontaneous Nucleation and Growth of Graphene Flakes on Copper Foil in the Absence of External Carbon Precursor in Chemical Vapor Deposition

Effect of Growth Pressure on Epitaxial Graphene Grown on 4H-SiC Substrates by Using Ethene Chemical Vapor Deposition

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Evaluation of Transport Parameters in MoS₂/Graphene Junction Devices Fabricated by Chemical Vapor Deposition

Evaluation of Transport Parameters in MoS₂/Graphene Junction Devices Fabricated by Chemical Vapor Deposition