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Towards the controlled CVD growth of graphitic B-C-N atomic layer films： The key role of B-C delivery molecular precursor

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Nano Research 2016年第5期9卷 1221-1235页

作者： Hao wang Chong Zhao Lei Liu Zhi Xu Jiake wei Wenlong wang Xuedong Bai Enge wang In ternational Center for Quantum Materials School of Physics Peking University Beijing 100871 China beijing National Laboratory for Condensed Matter physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China Collaborative Innovation Center of Quantum Matter Beijing 100871 China

Graphene-like, ternary system B-C-N atomic layer materials promise highly tunable electronic properties and a plethora of potential applications. However, thus far, experimental synthesis of the B-C-N atomic layers normally yields a microscopic phase-segregated structure consisting of pure C and BN domains. Further, growing the truly ternary B-C-N phase layers with homogenous atomic arrangements has proven to be very challenging. Here, in designing a better- controlled process for the chemical vapor deposition （CVD） growth of B-C-N atomic layer films with the minimized C and BN phase segregation, we selected trimethyl borane （TMB）, a gaseous organoboron compound with pre-existing B--C bonds, as the molecular precursor to react with ammonia （NH3） gas that serves as the nitrification agent. The use of this unique B-C delivery precursor allows for the successful synthesis of high-quality and large-area B-C-N atomic layer films. Moreover, the TMB/NH3 reactant combination can offer a high level of tunability and control of the overall chemical composition of B-C-N atomic layers by regulating the relative partial pressure of two gaseous reactants. Electrical transport measurements show that a finite energy gap can be opened in the as-grown B-C-N atomic layers and its tunability is essentially dependent on the relative C to BN atomic compositions. On the basis of carefully controlled experiments, we show that the pre-existing B-C bonds in the TMB molecular precursor have played a crucial role in effectively reducing the C and BN phase segregation problem, thereby facilitating the formation of truly ternary B-C-N phase atomic layers.

关键词： graphitic B-C-N atomic layer chemical vapor deposition B-C delivery precursor minimized phase segregation

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Half-integer Shapiro steps in MgB_(2) focused He ion beam Josephson junctions

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Chinese physics B 2024年第8期33卷 483-489页

作者：殷大利蔡欣炜徐铁权孙瑞宁韩颖张焱王越甘子钊 Applied Superconductivity Center State Key Laboratory for Mesoscopic PhysicsSchool of PhysicsPeking UniversityBeijing 100871China

Half-integer microwave induced steps(Shapiro steps)have been observed in many different Josephson junction systems,which have attracted a lot of attention because they signify the deviation of current phase relation(CPR)and uncover many unconventional physical *** this article,we first report the discovery of half-integer Shapiro steps in MgB_(2)focused He ion beam(He-FIB)Josephson *** half-integer steps'dependence on microwave frequency,temperature,microwave power,and magnetic field is also *** find that the existence of half-integer steps can be controlled by the magnetic field periodically,which is similar to that of high temperature superconductor(HTS)grain boundary junctions,and the similarity of the microstructures between gain boundary junctions and He-FIB junctions is *** a consequence,we mainly attribute the physical origin of half-integer steps in MgB_(2)He-FIB junctions to the model that a He-FIB junction is analogous to a parallel junctions'*** results show that He-FIB technology is a promising platform for researching CPR in junctions made of different superconductors.

关键词： Josephson junction half-integer Shapiro steps MgB_(2) focused helium ion beam

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Layered kagome compound Na_(2)Ni_(3)S_(4)with topological flat band

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Chinese physics B 2024年第5期33卷 153-159页

作者：叶君耀林益浩王浩哲宋志达冯济谢韦伟贾爽 International Center for Quantum Materials School of PhysicsPeking UniversityBeijing 100871China Department of Chemistry Michigan State UniversityMI48824USA Hefei National Laboratory Hefei 230088China Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials Peking UniversityBeijing 100871China

We report structural and electronic properties of Na_(2)Ni_(3)S_(4),a quasi-two-dimensional compound composed of alternating layers of[Ni_(3)S_(4)]^(2-)and Na^(+).The compound features a remarkable Ni-based kagome lattice with a square planar configuration of four surrounding S atoms for each Ni *** and electrical measurements reveal a weak paramagnetic insulator with a gap of about 0.5 *** band structure calculation highlights a set of topological flat bands of the kagome lattice derived from the rotated dxz-orbital with C_(3)+T symmetry in the presence of crystal-field splitting.

关键词： kagome lattice flat band

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Elastic scattering of ^(13)C and ^(14)C isotopes on a ^(208)Pb target at energies of approximately five times the Coulomb barriers

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Chinese physics C 2024年第3期48卷 65-71页

作者：杨过段芳芳王康杨彦云孙志宇 Valdir Guimarães 庞丹阳陈文棣金磊许世伟马军兵马朋白真汪凌昊刘泉王惠仁吕冰锋郭松 Mukhi Kumar Raju 王秀华李荣华张玉虎周小红胡正国徐瑚珊 CAS Key Laboratory of High Precision Nuclear Spectroscopy Institute of Modern PhysicsChinese Academy of SciencesLanzhou 730000China school of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100080China Instituto de Física Universidade de São PauloRua do Matão1371São Paulo 05508-090SPBrazil school of physics and beijing Key Laboratory of Advanced Nuclear Materials and physics Beihang UniversityBeijing 100191China school of physics Science and Engineering Tongji UniversityShanghai 200092China school of physics and Optoelectronic Engineering Anhui UniversityHefei 230601China Department of physics GITAM School of ScienceGITAM UniversityVisakhapatnam 530045India

The elastic scattering angular distributions of ^(13)C at 340 MeV and ^(14)C at 294 MeV and 342 MeV on a ^(208)Pb target,which correspond to approximately five times the Coulomb barriers,were measured at the Radioactive Ion Beam Line in *** data were analyzed within the optical model and continuum-discretized coupled-channels(CDCC)framework,and the results of both calculations could effectively account for the experimental *** differential cross sections of elastic scattering revealed no particular suppression at the Coulomb nuclear interference peak angles,suggesting that the breakup coupling effects on the elastic scattering angular distributions were negligibly small in this incident energy *** contributions from the couplings with inelastic states to the elastic cross sections were of minor importance within the angular range covered by these experiments.

关键词： elastic scattering radioactive ion beam angular distribution optical model coupling effects

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Discovery of tip induced unconventional superconductivity on Weyl semimetal

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Science Bulletin 2017年第6期62卷 425-430页

作者： He wang Huichao wang Yuqin Chen Jiawei Luo Zhujun Yuan Jun Liu Yong wang Shuang Jia Xiong-Jun Liu jian wei Jian wang International Center for Quantum Materials School of Physics Peking University Beijing 100871 China Collaborative Innovation Center of Quantum Matter Beijing China Center of Electron Microscopy State Key Laboratory of Silicon Materials School of Materials Sdence and Engineering Zhejiang University Hangzhou 310027 China

Weyl fermion is a massless Dirac fermion with definite chirality,which has been long pursued since *** it has not been observed as a fundamental particle in nature,Weyl fermion can be realized as low-energy excitation around Weyl point in Weyl semimetal,which possesses Weyl fermion cones in the bulk and nontrivial Fermi arc states on the surface. As a firstly discovered Weyl semimetal,Ta As crystal possesses 12 pairs of Weyl points in the momentum space,which are topologically protected against small perturbations. Here,we report for the first time the tip induced superconductivity on Ta As crystal by point contact spectroscopy. The zero bias conductance peak as well as a conductance plateau with double conductance peaks and sharp double dips are observed in the point contact spectra simultaneously,indicating unconventional superconductivity. Our further theoretical study suggests that the induced superconductivity may have nontrivial topology. The present work opens a new route in investigating the novel superconducting states based on Weyl materials.

关键词： Tip induced unconventional superconductivity Topological superconductivity Weyl semimetal TaAs Point contact spectroscopy

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Investigation of point-contact Andreev reflection on magnetic Weyl semimetal Co3Sn2S2

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Science china(physics,Mechanics & Astronomy) 2020年第8期63卷 107-113页

作者： He wang YanZhao Liu HuiBin Zhou HaoRan Ji Jiawei Luo Jiawei Zhang TianHeng wei PinYuan wang Shuang Jia Jian wang Department of physics Capital Normal UniversityBeijing 100048China International Center for Quantum Materials School of PhysicsPeking UniversityBeijing 100871China Collaborative Innovation Center of Quantum Matter Beijing 100871China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of SciencesBeijing 100190China beijing Academy of Quantum Information Sciences Beijing 100193China

Magnetic Weyl semimetals(WSMs)with broken time-reversal symmetry(TRS)hosting topological band structures are expected to provide an ideal platform for investigating topological superconductivity and ***,the experimental verification of magnetic WSMs is very *** recently,the kagome magnet Co3Sn2S2 was confirmed to be a magnetic WSM by both angle-resolved photoemission spectroscopy and scanning tunneling spectroscopy and consequently has become the focus of great *** paper reports a point-contact Andreev-reflection spectroscopy(PCARS)investigation on the(001)surface and the side surface of the Co3Sn2S2 single crystals,*** measurements from the sample’s(001)and side surfaces provide experimental evidence for transport spin polarization in the Co3Sn2S2 magnetic ***,the superconducting proximity effect in the Co3Sn2S2 single crystal is successfully *** point-contact spectra(PCS)along the in-plane direction cannot be well fitted by theoretical models based on s-wave pairing,indicating that possible triplet p-wave superconductivity may be triggered at the interface,which paves the way for the future exploration of the topological superconductivity and Majorana states in broken TRS WSMs.

关键词： magnetic Weyl semimetal point contact pairing symmetry superconducting proximity effect

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Defect suppression and energy level alignment in formamidinium-based perovskite solar cells

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Journal of Energy Chemistry 2022年第4期31卷 65-72页

作者： Yi wang Xiaobing wang Chenhui wang Renying Cheng Lanxin Zhao Xu wang Xuewen Zhang Jingzhi Shang Huang Zhang Lichen Zhao Yongguang Tu wei Huang Frontiers Science Center for Flexible Electronics Xi’an Institute of Flexible Electronics(IFE)&Xi’an Institute of Biomedical Materials and EngineeringNorthwestern Polytechnical UniversityXi’an 710072ShaanxiChina Engineering Research Centre of Environment-Friendly Functional Materials Ministry of EducationFujian Engineering Research Centre of Green Functional MaterialsHuaqiao UniversityXiamen 361021FujianChina Honors College Northwestern Polytechnical UniversityXi’an 710072ShaanxiChina State Key Laboratory for Artificial Microstructure and Mesoscopic physics School of PhysicsFrontiers Science Center for Nano-optoelectronics&Collaborative Innovation Center of Quantum MatterPeking UniversityBeijing 100871China Key Laboratory of Flexible Electronics(KLoFE)&Institution of Advanced Materials(IAM) Jiangsu National Synergetic Innovation Center for Advanced Materials(SICAM)Nanjing Tech UniversityNanjing 211816JiangsuChina Key Laboratory for Organic Electronics&Information Displays(KLOEID)&Institute of Advanced Materials(IAM) Nanjing University of Posts and TelecommunicationsNanjing 210023JiangsuChina

The vast majority of high-performance perovskite solar cells(PSCs) are based on a formamidinium lead iodide(FAPbI_(3))-dominant composition. Nevertheless, the FA-based perovskite films suffer from undesirable phase transition and defects-induced non-ideal interfacial recombination, which significantly induces energy loss and hinders the improvement of device performance. Herein, we employed 4-fluorophenylmethylammonium iodide(F-PMAI) to modulate surface structure and energy level alignment of the FA-based perovskite films. The superior optoelectronic films were obtained with reduced trap density, pure α-phase FAPbI_(3) and favorable energy band bending. The lifetime of photogenerated charge carriers increased from 489.3 ns to 1010.6 ns, and a more “p-type” perovskite film was obtained by the post-treatment with F-PMAI. Following this strategy, we demonstrated an improved power conversion efficiency of 22.59% for the FA-based PSCs with an open-circuit voltage loss of 399 m V.

关键词： Perovskite solar cells Defect suppression Energy level alignment Phase transition 4-Fluorophenylmethylammonium iodide

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Hemodynamic changes in hepatic sinusoids of hepatic steatosis mice

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World Journal of Gastroenterology 2019年第11期25卷 1355-1365页

作者： Jing Fan Chong-Jiu Chen Yu-Chen wang wei Quan Jian-wei wang wei-Guang Zhang Department of Anatomy Histology and EmbryologySchool of Basic Medical SciencesPeking University Health Science Center

BACKGROUND Fatty liver(FL) is now a worldwide disease. For decades, researchers have been kept trying to elucidate the mechanism of FL at the molecular level, but rarely involve the study of morphology and medical physics. Traditionally, it was believed that hemodynamic changes occur only when fibrosis occurs, but it has been proved that these changes already show in steatosis stage, which may help to reveal the pathogenesis and its progress. Because the pseudolobules are not formed during the steatosis stage, this phenomenon may be caused by the compression of the liver microcirculation and changes in the *** To understand the pathogenesis of hepatic steatosis and to study the hemodynamic changes associated with hepatic *** Eight-week-old male C57 BL/6 mice were divided into three groups randomly(control group, 2-wk group, and 4-wk group), with 16 mice per group. A hepatic steatosis model was established by subcutaneous injection of carbon tetrachloride in mice. After establishing the model, liver tissue from mice was stained with hematoxylin and eosin(HE), and oil red O stains. Blood was collected from the angular vein, and hemorheological parameters were estimated. A two-photon fluorescence microscope was used to examine the flow properties of red blood cells in the hepatic *** Oil red O staining indicated lipid accumulation in the liver after CCl_4 *** staining indicated narrowing of the hepatic sinusoidal vessels. No significant difference was observed between the 2-wk and 4-wk groups of mice onmorphological examination. Hemorheological tests included whole blood viscosity(mPas, γ = 10 s-1/γ = 100 s-1)(8.83 ± 2.22/4.69 ± 1.16, 7.73 ± 2.46/4.22 ±1.32, and 8.06 ± 2.88/4.22 ± 1.50), red blood cell volume(%)(51.00 ± 4.00, 42.00 ±5.00, and 40.00 ± 3.00), the content of plasma fibrinase(g/L)(3.80 ± 0.50, 2.90 ±0.80, and 2.30 ± 0.70), erythrocyte deformation index(%)(44.49 ± 5.81, 48.00 ±15.29, and 44.36 ± 15.01), eryt

关键词： Hepatic steatosis Hemodynamics Hepatic sinusoids Two-photon fluorescence microscopy Carbon tetrachloride

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Watts-level ultraviolet-CLED integrated light sources for efficient surface and air sterilization

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Journal of Semiconductors 2022年第7期43卷 61-67页

作者： wei Luo Tai Li Yongde Li Houjin wang Ye Yuan Shangfeng Liu weiyun wang Qi wang Junjie Kang Xinqiang wang Songshan Lake Materials Laboratory Dongguan 523808China State Key Laboratory of Artificial Microstructure and Mesoscopic physics school of physics Nano-Optoelectronics Frontier Center of Ministry of EducationPeking UniversityBeijing 100871China Dongguan Institute of Opto-Electronics Peking UniversityDongguan 523808China

With the epidemic of the coronavirus disease(COVID-19) infection, AlGaN-based ultraviolet-C light emitting diodes(UVC-LEDs) have attracted widespread attention for their sterilization application. However, the sterilization characters of high power integrated light sources(ILSs) haven’t been widely investigated before utilizing in public sanitary security. In this work,by integrating up to 195 UVC-LED chips, high power UVC-LED ILSs with a light output power(LOP) of 1.88 W were demonstrated. The UVC-LED ILSs were verified to have efficient and rapid sterilization capability, which have achieved more than99.9% inactivation rate of several common pathogenic microorganisms within 1 s. In addition, the corresponding air sterilization module based on them was also demonstrated to kill more than 97% of Staphylococcus albus in the air of 20 m3 confined room within 30 min. This work demonstrates excellent sterilization ability of UVC-LED ILSs with high LOP, revealing great potential of UVC-LEDs in sterilization applications in the future.

关键词： ultraviolet-C LED integrated light source surface sterilization air sterilization

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竖直周期外驱力下的颗粒碰撞自组织研究

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物理实验 2024年第2期44卷 58-63页

作者：赵梓茗王伟周路群北京大学物理学院北京100871

对竖直方向振动诱导的颗粒碰撞进行了理论和实验的探究.按照近似原则选取恰当参量,在准理想气体近似下对颗粒系统做极限假设,用热力学方法分析系统得出系统状态量服从的微分方程,针对该方程不可解析求解问题,提出了有效的修正方法并做... 详细信息

对竖直方向振动诱导的颗粒碰撞进行了理论和实验的探究.按照近似原则选取恰当参量,在准理想气体近似下对颗粒系统做极限假设,用热力学方法分析系统得出系统状态量服从的微分方程,针对该方程不可解析求解问题,提出了有效的修正方法并做级数修正.基于热力学输运和逐级展开研究受竖直驱动的颗粒系统的碰撞,展示了对颗粒系统的的研究思路,对文献中没有指明的恒温近似做进一步处理,给出温度分布方程和一阶修正,证明该近似在实验条件下成立.

关键词：颗粒动力学自组织周期驱动

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