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Density functional theory calculation of the properties of carbon vacancy defects in silicon carbide

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Nanotechnology and Precision Engineering 2020年第4期3卷 211-217页

作者： XiuhongWang Junlei Zhao Zongwei Xu Flyura Djurabekova Mathias Rommel Ying Song Fengzhou Fanga State Key Laboratory of Precision Measuring Technology&Instruments Centre of MicroNano Manufacturing TechnologyTianjin UniversityTianjin 300072China Department of Physics and Helsinki Institute of Physics University of HelsinkiP.O.Box 43FI-00014 HelsinkiFinland Department of Electrical and Electronic Engineering Southern University of Science and TechnologyShenzhen 518055China Fraunhofer Institute for Integrated Systems and Device Technology IISB Schottkystrasse 1091058 ErlangenGermany

As a promisingmaterial for quantumtechnology,silicon carbide(SiC)has attracted great interest inmaterials *** vacancy is a dominant defect in ***,understanding the properties of this defect is critical to its application,and the atomic and electronic structures of the defects needs to be *** this study,density functional theorywas used to characterize the carbon vacancy defects in hexagonal(h)and cubic(k)lattice *** zero-phonon line energies,hyperfine tensors,and formation energies of carbon vacancies with different charge states(2−,−,0,+and 2+)in different supercells(72,128,400 and 576 atoms)were calculated using standard Perdew-Burke-Ernzerhof and Heyd-Scuseria-Ernzerhof *** show that the zero-phonon line energies of carbon vacancy defects are much lower than those of divacancy defects,indicating that the former is more likely to reach the excited state than the *** hyperfine tensors of VC+(h)and VC+(k)were *** of the calculated hyperfine tensor with the experimental results indicates the existence of carbon vacancies in SiC *** calculation of formation energy shows that the most stable carbon vacancy defects in the material are VC 2+(k),VC+(k),VC(k),VC−(k)and VC 2−(k)as the electronic chemical potential increases.

关键词： Density functional theory Silicon carbide carbon vacancy

Synthesis of carbon nitride in moist environments:A defect engineering strategy toward superior photocatalytic hydrogen evolution reaction

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Journal of Energy Chemistry 2021年第3期30卷 403-413页

作者： Shuquan Huang Feiyue Ge Jia Yan Hongping Li Xingwang Zhu Yuanguo Xu Hui Xu Huaming Li School of Chemistry and Chemical Engineering Institute for Energy ResearchJiangsu UniversityZhenjiang 212013JiangsuChina Department of Applied Biology and Chemical Technology and the State Key Laboratory of Chirosciences The Hong Kong Polytechnic UniversityHung HomHong KongChina

Intimate understanding of the synthesis-structure-activity relationships is an accessible pathway to overcome the intrinsic challenges of carbon nitride(g-C_(3)N_(4))*** work looks in the effects of humidity of the synthesis process to the morphology,chemical structure,band structure as well as the photocatalytic activity of g-C_(3)N_(4) *** g-C_(3)N_(4) samples were prepared by heating melem in four gas environments:dry Ar,dry Air,moist Ar and moist *** photocatalytic activity measurements revealed that the samples synthesized in moist inert and oxidic gases environments displayed 20 and 10 times the photocata lytic H_(2) evolution activity of the samples synthesized in dry inert and oxidic gases environments,*** reasons for this remarkable variety in photocata lytic activities had been through *** all,the terminations of the carbon vacancies were identified as the dominant factor in enhancing H_(2) evolution *** work here thus demonstrating an example of defect engineering.

关键词： H_(2)evolution,g-C_(3)N_(4) carbon vacancy Terminal functional groups

Mechanism on carbon Vacancies in Polymeric carbon Nitride for CO2 Photoreduction

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Chinese Journal of Structural Chemistry 2020年第12期39卷 2068-2076,2053页

作者： LIU Shao-Hua LI Yi DING Kai-Ning CHEN Wen-Kai ZHANG Yong-Fan LIN Wei State Key Laboratory of Photocatalysis on Energy and Environment College of ChemistryFuzhou UniversityFuzhou 350108China Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry Xiamen 361005China

Defect engineering has being regarded as one of the effective ways to regulate chemical and electronic structure of ***,our collaborative work has shown experimentally that carbon vacancy on polymeric carbon nitride(CV)can greatly improve the CO2 to CO conversion with a 45-fold improvement over the polymeric carbon nitride(***.,2019,58,1134).In order to clarify the detailed mechanism of promotion,we have systematically studied the electronic properties of CV and hydrogenated CV(CV+H)as well as the effective CO2 reduction reaction through density functional theory *** found that it is the synergistic effect for the CO2 reduction reaction in the CV systems,as the onset potentials of several CVs are much lower than that of the polymeric carbon *** particular,the onset potentials of CV1,CV2,and CV2+H are around 0.9~1.5 eV with a strong chemisorbed CO2 on *** with the analysis of the electronic properties,our results confirm that defect engineering increases the lifetime of photo-generated charges,improves photocatalytic activity,and promotes the CO2 reduction reaction on the defected polymeric carbon nitrides.

关键词： polymeric carbon nitride(PCN) carbon vacancy reaction mechanism CO2 reduction density functional theory(DFT)

Electron paramagnetic resonance characterization of aluminum ion implantation-induced defects in 4H-SiC

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Nanotechnology and Precision Engineering 2019年第4期2卷 157-162页

作者： Xiuhong Wang Zongwei Xua Mathias Rommel Bing Dong Le Song Clarence Augustine TH Tee Fengzhou Fang State Key Laboratory of Precision Measuring Technology&Instruments Tianjin UniversityTianjin 300072China Fraunhofer Institute for Integrated Systems and Device Technology(IISB) Schottkystrasse 10Erlangen 91058Germany Department of Electrical Engineering Faculty of EngineeringUniversity of MalayaKuala Lumpur 50603Malaysia Centre of Advanced Research Enabler Facility Faculty of EngineeringUniversity of MalayaKuala Lumpur 50603Malaysia

Deep-level defects in silicon carbide(SiC)are critical to the control of the performance of SiC electron *** this paper,deep-level defects in aluminumion-implanted 4H-SiC after high-temperature annealingwere studied using electron paramagnetic resonance(EPR)spectroscopy at temperatures of 77 K and 123 K under different illumination *** showed that the main defect in aluminum ion-implanted 4H-SiC was the positively charged carbon vacancy(VC+),and the higher the doping concentration was,the higher was the concentration of VC+.Itwas found that the type of material defectwas independent of the doping concentration,although more VC+defects were detected during photoexcitation and at lower *** results should be helpful in the fundamental research of p-type 4H-SiC fabrication in accordance with functional device development.

关键词： Electron paramagnetic resonance Silicon carbide Defects carbon vacancy

Characteristics of Ni-based ohmic contacts on n-type 4H-SiC using different annealing methods

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Nanotechnology and Precision Engineering 2021年第1期4卷 44-47页

作者： Ziwei Zhou Weiwei He Zhenzhong Zhang Jun Sun Adolf Schöner Zedong Zheng Research and Development Department BASiC Semiconductor Ltd.Shenzhen 518000China Department of Electrical Engineering Tsinghua UniversityBeijing 100084China

Nickel is an excellent ohmic-contact metal on *** paper discusses the formation mechanism of nickel ohmic contact on 4HSiC by assessing the electrical properties and microstructural *** high-temperature annealing,the phase of nickel-silicon compound can be observed with X-ray diffraction,and the contact resistance also changes.A comparative experiment was designed to use X-ray diffraction and energy-dispersive spectroscopy to clarify the difference of ohmic-contact material composition and elemental analysis between samples prepared using pulsed laser annealing and rapid thermal *** is found that more Ni2Si and carbon vacancies formed at the interface in the sample prepared using pulsed laser annealing,resulting in a better ohmic-contact characteristic.

关键词： Laser annealing Rapid thermal annealing Ohmic contact Ni 4H-SiC carbon vacancy

Ohmic Contact Properties of Multi-Metal Films on n-Type 4H-SiC

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Journal of Semiconductors 2007年第2期28卷 149-153页

作者：韩茹杨银堂王平崔占东李亮西安电子科技大学宽禁带半导体材料与器件教育部重点实验室西安710071 中国电子科技集团公司第13研究所石家庄050051

An investigation of Au/Ti/Ni and Au/Ti/Pt ohmic contacts to n-type 4H-SiC and the behavior of metal films on SiC with thermal anneals is reported. Specific contact resistance as low as 2. 765 x 10^-6Ω·cm^2 was achieved after rapid thermal annealing in N2 for 2min at 950℃. SIMS analysis shows that the formation of Ni silicide after annealing supported a number of carbon atoms＇ outdiffusion from the SiC to form interstitial compound TiC. This process can create abundant C vacancies near the interface. It is the carbon defect layer that enhances the defect-assisted tunneling. The interface band structure within the defect level could make it clear why the metal-SiC contacts become ohmic during annealing.

关键词： silicon carbide ohmic contact carbon vacancy interface band structure