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Trap states induced by reactive ion etching in AlGaN/GaN high-electron-mobility transistors

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Chinese Physics B 2015年第11期24卷 460-463页

作者：罗俊赵胜雷宓珉瀚侯斌杨晓蕾张进成马晓华郝跃 Key Laboratory of Wide Band-Gap Semiconductor materials and Devices School of Microelectronics Xidian University School of advanced materials and Nanotechnology Xidian University

Frequency-dependent conductance measurements were carried out to investigate the trap states induced by reactive ion etching in A1GaN/GaN high-electron-mobility transistors （HEMTs） quantitatively. For the non-recessed HEMT, the trap state density decreases from 2.48 × 1013 ***-1 at an energy of 0.29 eV to 2.79 × 1012 ***-1 at ET = 0.33 eV. In contrast, the trap state density of 2.38 × 1013-1.10× 1014 ***-1 is located at ET in a range of 0.30-0.33 eV for the recessed HEMT. Thus, lots of trap states with shallow energy levels are induced by the gate recess etching. The induced shallow trap states can be changed into deep trap states by 350 ℃ annealing process. As a result, there are two different types of trap sates, fast and slow, in the annealed HEMT. The parameters of the annealed HEMT are ET = 0.29-0.31 eV and DT = 8.16× 1012-5.58 × 1013 ***-1 for the fast trap states, and ET = 0.37-0.45 eV and DT = 1.84×1013- 8.50 × 1013 ***-1 for the slow trap states. The gate leakage currents are changed by the etching and following annealing process, and this change can be explained by the analysis of the trap states.

关键词： AlGaN/GaN high-electron mobility transistors (HEMTs) annealing reactive ion etching trapstates

Microwave dielectric high-entropy ceramic Li(Gd_(0.2)Ho_(0.2)Er_(0.2)Yb_(0.2)Lu_(0.2))GeO_(4) with stable temperature coefficient for low-temperature cofired ceramic technologies

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Journal of materials Science & Technology 2021年第34期93卷 28-32页

作者： Huaicheng Xiang Lei Yao Junqi Chen Aihong Yang Haitao Yang Liang Fang Shenzhen Key Laboratory of Special Functional materials Shenzhen Engineering Laboratory for Advanced Technology of CeramicsGuangdong Research Center for Interfacial Engineering of Functional MaterialsCollege of Materials Science and EngineeringShenzhen UniversityShenzhen 518060China Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province.college of Physics and Optoelectronic Engineering Shenzhen UniversityShenzhen 518060China Guangxi Key Laboratory of Optical and Electronic materials and Devices College of Materials Science and EngineeringGuilin University of TechnologyCuilin 541004China

High-entropy ceramics are new single-phase materials with at least four cation or anion *** large configurational entropy is believed to enhance the simultaneous solubility of many components,which can be used to optimize certain *** this work,a high-entropy oxide,Li(Gd_(0.2)Ho_(0.2)Er_(0.2)Yb_(0.2)Lu_(0.2))GeO_(4)(LRG)was explored as a microwave dielectric ceramic for lowtemperature cofired ceramic *** LRG high-entropy ceramic with an olivine structure formed in the sintering temperature range of 1020-1100℃.The minimal distortion(5×10^(-4))of the[RO_(6)]octahedron led to a stable temperature coefficient of resonant frequency(τf)of-5.3 to-2.9 ppm/℃.Optimal microwave dielectric properties were achieved in the high-entropy ceramics at 1080℃ for 4 h with a relative density of 94.9%,a relative permittivity(ε_(r))of 7.2,and a quality factor(Q×f)of 29000 GHz(at15.3 GHz).For low-temperature cofired ceramic technology applications,the sintering temperature of the LRG high-entropy ceramic was reduced to 900℃ by the addition of 3 wt%H_(3)BO_(3),which exhibited outstanding microwave dielectric properties(ε_(r)=7.6,Q×f=11700 GHz,and τ_(f)=-7.4 ppm/℃)and a good chemical compatibility with silver.

关键词： High-entropy ceramic Octahedral distortion Microwave dielectric properties Stableτ_(f)

Defect Engineering of Carbons for energy Conversion and Storage Applications

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energy & Environmental materials 2023年第3期6卷 264-285页

作者： Xianyou Luo Heng Zheng Wende Lai Ping Yuan Shengwei Li De Li Yong Chen Guangdong Key Laboratory for Hydrogen energy Technologies School of Materials Science and Hydrogen EnergyFoshan UniversityFoshan 528000China State Key Laboratory of Marine Resource Utilization in South China Sea Hainan Provincial Key Laboratory of Research on Utilization of Si-Zr-Ti ResourcesHainan UniversityHaikou 570228China Key Laboratory of advanced energy materials Chemistry(Ministry of Education) Nankai UniversityTianjin 300071China

Sustainable energy conversion and storage technologies are a vital prerequisite for neutral future *** this end,carbon materials with attractive features,such as tunable pore architecture,good electrical conductivity,outstanding physicochemical stability,abundant resource,and low cost,have used as promising electrode materials for energy conversion and *** engineering could modulate the structures of carbon materials,thereby affecting their electronic *** presence of defects on carbons may lead to asymmetric charge distribution,change in geometrical configuration,and distortion of the electronic structure that may result in unexpected electrochemical *** this review,recent advances in defects of carbons used for energy conversion and storage were examined in terms of types,regulation strategies,and fine characterization means of *** applications of such carbons in supercapacitors,rechargeable batteries,and electrocatalysis were also *** perspectives toward the development of defect engineering carbons were *** all,novel insights related to improvement in high-performance carbon materials for future energy conversion and storage applications were provided.

关键词： carbon materials defect engineering electrocatalysis rechargeable batteries supercapacitors

Natural overlaying behaviors push the limit of planar cyclic deformation performance in few-layer MoS_(2) nanosheets

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InfoMat 2023年第9期5卷 64-77页

作者： Peifeng Li Guangjie Zhang Zhuo Kang Xin Zheng Yong Xie Chunyuan Liang Yizhi Zhang Xiaoyang Fang Rong Sun Zhiquan Liu Yeqiang Bu Yang Lu Yue Zhang Shenzhen Institute of advanced Electronic materials Shenzhen Institute of Advanced TechnologyChinese Academy of SciencesShenzhenthe People's Republic of China CAS Key Laboratory of Standardization and Measurement for Nanotechnology CAS Center for Excellence in NanoscienceNational Center for Nanoscience and TechnologyBeijingthe People's Republic of China Beijing advanced Innovation Center for materials Genome Engineering Beijing Key Laboratory for Advanced Energy Materials and TechnologiesUniversity of Science and Technology BeijingBeijingthe People's Republic of China State Key Laboratory for advanced Metals and materials School of Materials Science and EngineeringUniversity of Science and Technology BeijingBeijingthe People's Republic of China college of Chemistry and materials Engineering Zhejiang A&F UniversityHangzhouthe People's Republic of China Center for X-mechanics School of Aeronautics and AstronauticsZhejiang UniversityHangzhouPeople's Republic of China Department of Mechanical Engineering The University of Hong KongHong Kongthe People's Republic of China

As a typical two-dimensional(2D)transition metal dichalcogenides(TMDCs)material with nonzero band gap,MoS_(2)has a wide range of potential applications as building blocks in the field of *** stability and reliability of the corresponding nanoelectronic devices depend critically on the mechanical performance and cyclic reliability of 2D MoS_(2).Although an in situ technique has been used to analyze the mechanical properties of 2D materials,the cyclic mechanical behavior,that is,fatigue,remains a major challenge in the practical application of the *** study was aimed at analyzing the planar cyclic performance and deformation behavior of three-layer MoS_(2)nanosheets(NSs)using an in situ transmission electron microscopy(TEM)variable-amplitude uniaxial low-frequency and cyclic loading-unloading tensile acceleration *** also elucidated the strengthening effect of the natural overlaying affix fragments(other external NSs)or wrinkle folds(internal folds from the NS itself)on cycling performances and service life of MoS_(2)NSs by delaying the whole process of fatigue crack initiation,propagation,and *** results have been confirmed by molecular dynamics(MDs)*** overlaying enhancement effect effectively ensures the long-term reliability and stability of nanoelectronic devices made of few-layer 2D materials.

关键词： cyclic deformation performance few-layer MoS_(2) in situ TEM nanomechanics natural overlays strengthening effect

Performance measurement and evaluation of an ionic liquid electrospray thruster

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Chinese Journal of Aeronautics 2023年第3期36卷 1-15页

作者： Chengjin HUANG Jianling LI Mu LI School of Power and energy Northwestern Polytechnical UniversityXi’an 710072China Shenzhen Key Laboratory of Ultraintense Laser and advanced Material Technology Center for Advanced Material Diagnostic Technologyand College of Engineering PhysicsShenzhen Technology UniversityShenzhen 518118China

As a novel micro-propulsion system for small satellites(from micro to nano),the ionic liquid electro spray propulsion system is a promising ***,performance measurement and evaluation of the Ionic Liquid Electrospray Thruster(ILET)is one of the most challenging issues for practical application,due to the difficulties in the development of a prototype and direct measurements of micro-thrust and small flow *** address this issue,a Modular Ionic Liquid Electrospray Thruster(MILET)prototype is constructed,and a diagnostic system for thrust and mass flow rate is specially developed based on an analytical balance *** the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate as the propellant,a series of experiments is carried out on the MILET prototype under a wide operating condition through changing the applied voltage to control the *** different applied voltages,the thrust and the mass flow rate of the propellant are directly *** propulsive performance parameters of the thruster,such as thrust,specific impulse,thrust-to-power ratio,thruster efficiency,etc.,are comprehensively ***,a performance comparison is made between the MILET and other representative *** a relatively low applied voltage ranging from 1550 V to 2000 V,the MILET achieves a quasi-constant specific impulse of 1263 s with the averaged thrust-to-power ratio of 65.2μN/W and thruster efficiency of 40.7%.The performance of ILET is also compared with other typical electric *** results demonstrate that the ILET exhibits an excellent ability of minimalization with high specific impulse and thruster efficiency,which guarantees a great superiority in micro ***,the ways to further improve the performance of ILET are discussed,which further confirms the potential prospect of *** present result helps to advance the development and application of ILET.

关键词： Electrospray thruster Ionic liquids Performance measurement Performance estimation Micro-propulsion

Electroreduction of CO_(2) to C_(2)H_(4) Regulated by Spacing Effect:Mechanistic Insights from DFT Studies

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energy Material Advances 2023年第1期4卷 294-303页

作者： Xinze Bi Yifan Yan Hongzhi Wang Yuezhu Zhao Jiatao Zhang Mingbo Wu college of New energy College of Chemical EngineeringState Key Laboratory of Heavy Oil ProcessingChina University of Petroleum(East China)Qingdao 266580China Beijing Key Laboratory of Construction-Tailorable advanced Functional materials and Green Applications School of Chemistry and Chemical EngineerBeijing Institute of TechnologyBeijing 100081China

It is crucial to construct an efficient catalyst with high activity and excellent selectivity for realizing CO_(2) electroreduction reaction(CO_(2)ER)to high-value-added chemicals,especially the C2 *** functional theory(DFT)provides a powerful tool for investigating the promotional effect on C2 selectivity of finely tuned catalyst structures,which is currently difficult to control using experimental techniques,such as interatomic *** the work,5 Cu_(2)O catalyst models are constructed with different Cu-Cu atomic spacing(d_(Cu-Cu)).The results of DFT calculations show that adjusting the d_(Cu-Cu) can effectively tailor the electronic structures of active sites,enhance catalytic activity,and improve product ***,the Cu atom pair spaced at d_(Cu-Cu)=2.5Åcould optimize the adsorption configuration of*CO and enhance the binding strength of*CO,thus improving*CO adsorption energy and reducing the energy barrier of C-C *** work proves the feasibility of spacing effect in enhancing the C_(2)H_(4) selectivity of CO_(2) ER and provides a new idea for the catalyst modification for other reactions of polyprotons-coupled electrons.

关键词： catalyst selectivity spacing

Single-atom Sn-Zn pairs in CuO catalyst promote dimethyldichlorosilane synthesis

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National Science Review 2020年第3期7卷 600-608页

作者： Qi Shi Yongjun Ji Wenxin Chen Yongxia Zhu Jing Li Hezhi Liu Zhi Li Shubo Tian Ligen Wang Ziyi Zhong Limin Wang Jianmin Ma Yadong Li Fabing Su Gripm advanced materials Co. Ltd State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of Sciences Zhongke Langfang Institute of Process Engineering Beijing Key Laboratory of Construction Tailorable advanced Functional materials and Green Applications School of Materials Science and Engineering Beijing Institute of Technology Department of Chemistry Tsinghua University college of Engineering Guangdong Technion–Israel Institute of Technology (GTIIT) Technion–Israel Institute of Technology (IIT) School of Physics and Electronics Hunan University Institute of Industrial Chemistry and energy Technology Shenyang University of Chemical Technology

Single-atom catalysts are of great interest because they can maximize the atom-utilization efficiency and generate unique catalytic properties; however, much attention has been paid to single-site active components, rarely to catalyst promoters. Promoters can significantly affect the activity and selectivity of a catalyst, even at their low concentrations in catalysts. In this work, we designed and synthesized Cu O catalysts with atomically dispersed co-promoters of Sn and Zn. When used as the catalyst in the Rochow reaction for the synthesis of dimethyldichlorosilane, this catalyst exhibited much-enhanced activity,selectivity and stability compared with the conventional Cu O catalysts with promoters in the form of nanoparticles. Density functional theory calculations demonstrate that single-atomic Sn substitution in the Cu O surface can enrich surface Cu vacancies and promote dispersion of Zn to its atomic levels. Sn and Zn single sites as the co-promoters cooperatively generate electronic interaction with the Cu O support, which further facilitates the adsorption of the reactant molecules on the surface, thereby leading to the superior catalytic performance.

关键词： dual single-atom promoters CuO catalyst dimethyldichlorosilane synthesis Rochow reaction catalytic performance

Effects of Al and Co doping on the structural stability and high temperature cycling performance of LiNi_(0.5)Mn_(1.5)O_(4) spinel cathode materials

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Chinese Journal of Chemical Engineering 2023年第9期61卷 201-209页

作者： Jianfeng Cheng Meixuan Li Yutong Wang Jiexiang Li Jiawei Wen Chunxia Wang Guoyong Huang college of New energy and materials China University of Petroleum(Beijing)Beijing 102249China State Key Laboratory of Heavy Oil Processing College of Chemical EngineeringChina University of Petroleum(Beijing)Beijing 102249China

The poor structural stability and capacity retention of the high-voltage spinel-type LiNi_(0.5)Mn_(1.5)O_(4)(LNMO)limits their further ***,Al and Co were doped in LNMO materials for a more stable structure and *** LNMO,LiNi_(0.45)Al_(0.05)Mn_(1.5)O_(4)(LNAMO)and LiNi_(0.45)Co_(0.05)Mn_(1.5)O_(4)(LNCMO)were synthesized by calcination at 900℃ for 8 h,which was called as solid-phase method and applied universally in ***,FT-IR and CV test results showed the synthesized samples have cation disordering Fd-3m space group ***,the incorporation of Al and Co increased the cation disordering of LNMO,thereby increasing the transfer rate of Li+.The SEM results showed that the doped samples performed more regular and *** EDS elemental analysis confirmed the uniform distribution of each metal element in the ***,the doped samples showed better electrochemical properties than undoped *** LNAMO and LNCMO samples were discharged with specific capacities of 116.3 mA·h·g^(-1)and 122.8 mA·h·g^(-1)at 1 C charge/discharge rate with good capacity retention of 95.8% and 94.8% after 200 cycles at room temperature,*** capacity fading phenomenon of the doped samples at 50℃ and 1 C rate was significantly ***,cations doping also enhanced the rate performance,especially for the LNCMO,the discharge specific capacity of 117.9 mA·h·g^(-1)can be obtained at a rate of 5 C.

关键词： High voltage spinel Al/Co doping High temperature cycling stability

[Zn4O] Cluster-Based Metal-Organic Frameworks as Catalysts for Conversion of CO2

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Chinese Journal of Chemistry 2019年第5期37卷 474-478页

作者： Wanzhen Qiao Tianqun Song Bin Zhao college of Chemistry College of Chemistry Key Laboratory of Advanced Energy Material Chemistry MOE Nankai University Tianjin 300071 China Department of Chemistry Tianjin University Tianjin 300072 China

Summary of main observation and conclusion One unique two-dimensional (2D) Zn-MOF {Na[Zz1.5(μ4-O)(L)]}n (1) was synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction. Four Zn atoms are bridged through μ4-O to form [Zn4O] clusters, which are further linked to form a 2D layer n etwork through shari ng Zn as vertexes. 1 exhibits high thermal stability up to 280 ℃ and keeps stable in comm on solve nts and water solutions with pH ranging from 1 to 13. The catalytic studies reveal that compound 1 exhibits excellent catalytic activity for cycloaddition of CO2 with epoxides into cyclic carb on ates un der mild conditions. Furthermore, 1 dem on strates good gen erality in CO2 coupli ng reactio n with extensive epoxides. Importantly, 1 can be reused for at least five times without significant reduction in catalytic ability.

关键词： Zn4O ability