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Kinetics of hydrogen constrained graphene growth on cu substrate

Nano Research 2024年第11期17卷 9284-9292页

作者： Xiucai Sun Shuang Lou Weizhi Wang Xuqin Liu Xiaoli Sun Yuqing Song Weimin Yang Zhongfan Liu Beijing Graphene Institute (BGI) Beijing 100095 China College of Mechanical and Electrical Engineering Beijing University of Chemical Technology Beijing 100029 China School of Instrument and Electronics North University of China Taiyuan 030051 China Center for Nanochemistry Beijing Science and Engineering Center for Nanocarbons Beijing National Laboratory for Molecular Science College of Chemistry and Molecular Engineering Peking University Beijing 100871 China

Chemical vapor deposition (CVD) has shown great promise for the large-scale production of high-quality graphene films for industrial applications. Atomic-scale theoretical studies can help experiments to deeply understand the graphene growth mechanism, and serve as theoretical guides for further experimental designs. Here, by using density functional theory calculations, ab-initio molecular dynamics simulations, and microkinetic analysis, we systematically investigated the kinetics of hydrogen constrained graphene growth on cu substrate. The results reveal that the actual hydrogen-rich environment of CVD results in CH as the dominating carbon species and graphene H-terminated edges. CH participated island sp2 nucleation avoids chain cyclization process, thereby improving the nucleation and preventing the formation of non-hexameric ring defects. The graphene growth is not simply C-atomic activity, rather, involves three main processes: CH species attachment at the growth edge, leading to a localized sp3 hybridized carbon at the connecting site;excess H transfer from the sp3 carbon to the newly attached CH;and finally dehydrogenation to achieve the sp2 reconstruction of the newly grown edge. The threshold reaction barriers for the growth of graphene zigzag (ZZ) and armchair (AC) edges were calculated as 2.46 and 2.16 eV, respectively, thus the AC edge grows faster than the ZZ one. Our theory successfully explained why the circumference of a graphene island grown on cu substrates is generally dominated by ZZ edges, which is a commonly observed phenomenon in experiments. In addition, the growth rate of graphene on cu substrates is calculated and matches well with existing experimental observations.

关键词： graphene growth chemical vapor deposition theoretical calculation cu substrate hydrogen constraint effect

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Theoretical investigations on the growth of graphene by oxygenassisted chemical vapor deposition

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Nano Research 2024年第6期17卷 4645-4650页

作者： Xiaoli Sun Chaojie Yu Yujia Yang Zhihao Li Jianjian Shi Wanjian Yin Zhongfan Liu Beijing Graphene Institute(BGI) Beijing 100095China School of Physics and Electronics Shandong Normal UniversityJinan 250014China College of Energy Soochow Institute for Energy and Materials InnovationsLight Industry Institute of Electrochemical Power SourcesSUDA-BGI Collaborative Innovation CenterSoochow UniversitySuzhou 215006China School of Electronic Engineering Chengdu Technological UniversityChengdu 611730China Center for Nanochemistry Beijing National Laboratory for Molecular SciencesCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China

Recently,graphene has drawn considerable attention in the field of electronics,owing to its favorable conductivity and high carrier *** to the industrialization of graphene is its high-quality microfabrication via chemical vapor ***,many problems remain in its preparation,such as the not fully understood cracking mechanism of the carbon source,the mechanism of its substrate oxidation,and insufficient defect repair *** help close this capability gap,this study leverages density functional theory to explore the role of O in graphene *** effects of cu substrate oxidation on carbon source cracking,nucleation barriers,crystal nucleus growth,and defect repairs are *** was found to reduce energy change during dehydrogenation,rendering the process ***,the adsorbed O in graphene or its cu substrate can promote defect repair and edge growth.

关键词： density functional theory oxygen-assisted graphene growth chemical vapor deposition cu substrate

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Enhancement of nucleation of diamond films deposited on copper substrate by nickel modification layer

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Transactions of Nonferrous Metals Society of China 2013年第3期23卷 667-673页

作者：刘学璋魏秋平翟豪余志明中南大学材料科学与工程学院长沙410083 中南大学粉末冶金国家重点实验室长沙410083

A Ni layer with a thickness of about 100 nm was sputtered on cu substrates,followed by an ultrasonic seeding with nanodiamond ***-quality diamond film with its crystalline grains close to thermal equilibrium shape was deposited on cu substrates by hot-filament chemical vapor deposition（HF-CVD）,and the sp2 carbon content was less than 5.56%.The nucleation and growth of diamond film were investigated by micro-Raman spectroscopy,scanning electron microscopy,and X-ray *** results show that the nucleation density of diamond on the Ni-modified cu substrates is 10 times higher than that on blank cu *** enhancement mechanism of the nucleation kinetics by Ni modification layer results from two effects：namely,the nanometer rough Ni-modified surface shows an improved absorption of nanodiamond particles that act as starting points for the diamond nucleation during HF-CVD process;the strong catalytic effect of the Ni-modified surface causes the formation of graphite layer that acts as an intermediate to facilitate diamond nucleation quickly.

关键词： diamond film nickel interlayer cu substrate chemical vapor deposition nucleation kinetics surface modification

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Growth behavior of CVD diamond in microchannels of cu template

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Transactions of Nonferrous Metals Society of China 2015年第6期25卷 2009-2017页

作者：刘学璋张雄伟余志明江西科技师范大学材料与机电学院南昌330013 中南大学材料科学与工程学院长沙410083

Deposition of diamond inside the trenches or microchannels by chemical vapor deposition （CVD） is limited by the diffusion efficiency of important radical species for diamond growth （H, CH3） and the pore depth of the substrate template. By ultrasonic seeding with nanodiamond suspension, three-dimensional （3D） penetration structure diamond was successfully deposited in cylindrical microchannels of cu template by hot-filament chemical vapor deposition. Micro-Raman spectroscopy and scanning electron microscopy （SEM） were used to characterize diamond film and the effects of microchannel depth on the morphology, grain size and growth rate of diamond film were comprehensively investigated. The results show that diamond quality and growth rate sharply decrease with the increase of the depth of cylindrical microchannel. Individual diamond grain develops gradually from faceted crystals into micrometer cluster, and finally to ballas-type nanocrystalline one. In order to modify the rapid decrease of diamond quality and growth rate, a new hot filament apparatus with a forced gas flow through cu microchannels was designed. Furthermore, the growth of diamond film by new apparatus was compared with that without a forced gas flow, and the enhancement mechanism was discussed.

关键词： chemical vapor deposition diamond template cu substrate microchannel

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