电子科技大学电子科学与工程学院太赫兹中心，四川 成都 611731
碘化铯（CsI）光电阴极广泛应用于超快诊断中，光电子的空间分布、能量分布、时间分布等与条纹变像管的整体性能有着密切的关联。本文联合粒子仿真软件Geant4和三维电磁软件CST实现了对CsI光电阴极的光电子产生与控制过程的全动态模拟。采用Geant4软件对CsI光电阴极的光电转换过程进行建模，分析了二次电子出射能量、时间、位置、角度等发射特性；通过数据交互，统计了出射光电子的分布规律，然后将其应用于CST中建立阴极发射模型，并在CST中设计出一款弧矢、子午方向上放大倍率皆为2的各向异性聚焦条纹变像管。
X射线光学 Geant4 联合仿真 碘化铯 光电发射特性 各向异性聚焦条纹变像管
Author Affiliations
Abstract
1 State Key Laboratory for Mesoscopic Physics & Department of Physics, Collaborative Innovation Center of Quantum Matter & Frontiers Science Center for Nano-optoelectronics, Beijing Academy of Quantum Information Sciences, Peking University, Beijing 100871, China
2 Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Kaiserslautern 67663, Germany
3 College of Physics Science & Technology, Hebei University, Baoding 071002, China
4 Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
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The two-dimensional electron gas (2DEG) generated at the LaAlO3/SrTiO3 interface has been in the focus of oxides research since its first discovery. Although oxygen vacancies play an important role in the generation of the insulator-to-metal transition of the SrTiO3 bare surface, their contribution at the LaAlO3/SrTiO3 interface remains unclear. In this work, we investigated a LaAlO3/SrTiO3 heterostructure with regional distribution of defect-based localized polar sites at the interface. Using static and time-resolved threshold photoemission electron microscopy, we prove that oxygen vacancies are induced near those polar sites, resulting in the increase of carrier density of the 2DEG states. In addition, oxygen-related surface states were uncovered, which we attributed to the release of lattice oxygen during the formation of oxygen vacancies. Such effects are mainly found spatially located around the defect sites at the buried interface, while other regions remain unaffected. Our results confirm that the itinerant electrons induced by oxygen vacancies can coexist with the charge transfer mechanism in the LaAlO3/SrTiO3 heterostructure, together leading to the formation of the metallic interface. These observations provide fundamental insights into the nature of LaAlO3/SrTiO3 interface based 2DEG and unique perspectives for potential applications.
two-dimensional electron gas photoemission electron microscopy strontium titanate defect states Opto-Electronic Science
2022, 1(7): 210011
Author Affiliations
Abstract
1 Key Laboratory of Space Applied Physics and Chemistry, Ministry of Education, and Shaanxi Key Laboratory of Optical Information Technology, School of Science, North Western Polytechnical University, Xi’an 710072, China
2 Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583, Singapore
3 LEES Program, Singapore-MIT Alliance for Research & Technology (SMART), Singapore 138602, Singapore
A polarization-insensitive plasmonic absorber is designed consisting of Au fishnet structures on a TiO2 spacer/Ag mirror. The fishnet structures excite localized surface plasmon and generate hot electrons from the absorbed photons, while the TiO2 layer induces Fabry–Perot resonance, and the Ag mirror acts as a back reflector. Through optimizing the TiO2 layer thickness, numerical simulation shows that 97% of the incident light is absorbed in the Au layer. The maximum responsivity and external quantum efficiency of the device can approach 5 mA/W and ～1%, respectively, at the wavelength of 700 nm.
plasmonic absorber Fabry–Perot resonance internal photoemission surface plasmon Chinese Optics Letters
2020, 18(5): 052402
1 北海道大学电子科学研究所, 日本 札幌 001-0020
3 北京大学物理学院, 北京 100871
对超快光电子显微技术的基本原理和主要应用进行了简单介绍。着重介绍了超快光电子显微镜在纳米光子学,特别是在表面等离激元光子学领域中的研究进展,主要包括近场成像、近场光谱以及时间分辨的动力学过程。这些研究有助于更直观深刻地理解表面等离激元的基本性质、不同模式之间的相互作用,以及更好地设计及拓展表面等离激元的应用。最后,对该技术的应用前景进行了展望。
超快光学 近场 光电子显微技术 表面等离激元 飞秒激光 时间分辨测量
1 南京理工大学 电子工程与光电技术学院, 南京 210094
2 微光夜视技术重点实验室, 西安 710065
基于超高真空光电阴极制备与表面分析互联装置开展了反射式GaAs光电阴极激活实验, 并利用扫描聚焦X射线光电子能谱对化学清洗后及Cs/O激活后的阴极表面进行了微区分析.通过X射线激发样品产生二次电子图像定位需要分析的微小区域, 更加准确地检测了阴极表面存在的杂质.检测发现化学清洗后的GaAs阴极样品会受到金属压片的二次污染, 出现钠、铯污染.表面分析和激活实验表明, 高温加热和激活并不能去除钠污染, 且此污染会影响表面砷的脱附, 阻碍激活过程中Cs、O的吸附, 降低阴极的光电发射性能.采用扫描聚焦X射线成像技术对阴极表面进行微区选点分析, 有助于更加准确地分析阴极激活前后的表面成分变化.
GaAs光电阴极 扫描聚焦X射线成像技术 微区分析 表面污染 光电发射 GaAs photocathode Scanning focused Xray imaging technology Microarea analysis Surface contamination Photoemission
Author Affiliations
Abstract
1 Research Institute for Electronic Science, Hokkaido University, Sapporo 001-0021, Japan
2 College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
We studied the near-field properties of localized surface plasmon resonances in finite linear gold nanochains using photoemission electron microscopy (PEEM). The localization of the electromagnetic field in the near-field region was mapped at high spatial resolution. By tuning the excitation laser wavelength, we can obtain the near-field spectra, from which the energy splitting between longitudinal (L) and transverse (T) plasmon modes can be revealed. In particular, the L-mode red shifts and the T-mode blue shifts with increasing chain length. The red shift of the L-mode is highly dependent on the gap distance. In contrast, the T-mode almost remains constant within the range of gap distance we investigated. This energy splitting between the L-mode and the T-mode of metallic chains is in agreement with previous far-field measurements, where it was explained by dipole-dipole near-field coupling. Here, we provide direct proof of this near-field plasmon coupling in nanochains via the above-described near-field measurements using PEEM. In addition, we explore the energy transport along the gold nanochains under excitation at oblique illumination via PEEM measurements together with numerical simulations.
surface plasmon resonance metallic nanochains near-field imaging photoemission electron microscopy Opto-Electronic Advances
2019, 2(4): 180030
东南大学 电子科学与工程学院 信息显示与可视化国际合作实验室, 江苏 南京 210096
表面等离激元共振衰减诱导热电子, 因其能量高、分布窄、打破半导体禁带宽度限制等特点被广泛应用于拓展半导体光电转换的响应光谱, 如拓展宽禁带半导体的响应光谱至可见光波段, 拓展硅的响应波段至近红外。此外, 还可以通过调节表面等离激元结构调控响应光谱和实现偏振探测, 在实现硅基近红外光电探测领域具有重要的应用价值。从表面等离激元以及表面等离激元内光电效应的机理出发, 综述了表面等离激元热电子原理在实现硅基近红外光电探测方面的研究进展, 并总结了表面等离激元结构的形貌, 尺寸、分布等因素对热电子的产生(外量子效率)和注入效率(内量子效率)的影响。最后展望了基于表面等离激元结构的硅基肖特基结近红外光电探测的研究方向。
表面等离激元 内光电效应 硅基 近红外 光电探测 surface plasmon internal photoemission effect (IPE) silicon-based near-infrared photoelectronic dectection 红外与激光工程
2019, 48(2): 0203002
北京大学物理学院人工微结构与介观物理国家重点实验室, 北京 100871
通过对激光脉冲频谱的相位、振幅或偏振进行调制，可以获得不同时域分布的激光脉冲。这些特性不同的激光脉冲在物理过程和光学器件研究中具有重要的应用。随着光发射电子显微镜、超灵敏探测光谱仪、扫描近场显微等技术的发展，激光脉冲整形技术在微纳米光学中的应用日益深入。总结了近年来激光脉冲整形与测量技术的发展，综述了激光脉冲整形在近场光学、光发射电子显微镜、单分子光谱中的应用研究进展。
物理光学 脉冲整形 超快光谱 光发射电子显微镜 单分子光谱 光学学报
2016, 36(10): 1026007
1 中南大学 先进材料超微结构与超快过程研究所, 湖南 长沙410083
2 Department of Physics and Astronomy, University of Rochester, Rochester, NY14627, USA
结合紫外光电子能谱(UPS)、X射线光电子能谱(XPS)和原子力显微镜(AFM)等实验手段系统研究了C8-BTBT沉积在层状MoS2基底上的界面能级匹配、薄膜生长和分子取向。研究发现C8-BTBT分子竖直生长在MoS2上,生长过程中界面的真空能级(VL)、最高占据态轨道(HOMO)和电离能(IP)都出现了非常规的弯曲现象。这种能级弯曲行为可归因于直立分子从界面相到体相的转变过程中,其分子倾斜角(θ)存在一定的渐变,这种渐变会在沿表面法线方向诱导出一系列的层间电偶极,最终导致能级的弯曲。同时θ的变化也会改变薄膜的表面极化强度,引起IP的逐渐减小。能级的弯曲在界面处形成类P-N结的效应会对C8-BTBT基电子器件的性能有很大的影响。
光电子能谱 能级匹配 分子取向 薄膜生长 photoemission spectroscopy (PES) C8-BTBT C8-BTBT energy level alignment molecular orientation film growth
