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High-efficiency CdTe/CdS core/shell nanocrystals in water enabled by photo-induced colloidal hetero-epitaxy of CdS shelling at room temperature

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Nano Research 2015年第7期8卷 2317-2328页

作者： Hakimeh Zare Maziar Marandi Somayeh Fardindoost Vijay Kumar Sharma Aydan Yeltik Omid Akhavan Hilmi Volkan Demir Nima Taghavinia Institute for Nanoscience and Nanotechnology Shafif University of Technology Tehran 14588 Iran Department of Physics Faculty of Sciences Arak University Arak 38156-8-8349 Iran Department of Physics Department of Electrical and Electronics Engineering and UNAM-Institute of Materials Science and Nanotechnology Bilkent University Ankara Turkey Luminous Center of Excellence for Semiconductor Lighting and Displays Microelectronics Division School of Electrical and Electronics Engineering and Physics and Applied Physics Division School of Physical and Mathematical Sciences Nanyang Technological University Singapore 639798 Singapore Physics Department ShafifUniversity of Technology Tehran 14588 Iran

We report high-efficiency CdTe/CdS core/shell nanocrystals synthesized in water by epitaxially growing CdS shells on aqueous CdTe cores at room temperature, enabled by the controlled release of S species under low-intensity ultraviolet （UV） light illumination. The resulting photo-induced dissociation of S2O2- ions conveniently triggers the formation of critical two-dimensional CdS epitaxy on the CdTe surface at room temperature, as opposed to initiating the growth of individual CdS core-only nanocrystals. This controlled colloidal hetero-epitaxy leads to a substantial increase in the photoluminescence （PL） quantum yield （QY） of the shelled nanocrystals in water （reaching 64%）. With a systematic set of studies, the maximum PL QY is found to be almost independent of the illuminating UV intensity, while the shell formation kinetics required for reaching the maximum QY linearly depends on the illuminating UV intensity. A stability study of the QD films in air at various temperatures shows highly improved thermal stability of the shelled QDs （up to 120 ℃ in ambient air）. These results indicate that the proposed aqueous CdTe/CdS core/shell nanocrystals hold great promise for applications requiring efficiency and stability.

关键词： CdTe/CDs,core/shell nanocrystal thermal stability photochemical

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High resolution scanning gate microscopy measurements on InAs/GaSb nanowire Esaki diode devices

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Nano Research 2014年第6期7卷 877-887页

作者： James L. Webb Olof Perssor Kimberly A. Dick Claes Thelander Rainer Timm Anders Mikkelsen division of Synchrotron Radiation Research Lund University Sweden Center forAnalysis and Synthesis Lund University Sweden division of Solid State Physics Lund University Sweden

Gated transport measurements are the backbone of electrical characterization of nanoscale electronic devices. Scanning gate microscopy (SGM) is one such gating technique that adds crucial spatial information, accessing the localized properties of semiconductor devices. Nanowires represent a central device concept due to the potential to combine very different materials. However, SGM on semiconductor nanowires has been limited to a resolution in the 50-100 nm range. Here, we present a study by SGM of newly developed III–V semiconductor nanowire InAs/GaSb heterojunction Esaki tunnel diode devices under ultra-high vacuum. Sub-5 nm resolution is demonstrated at room temperature via use of quartz resonator atomic force microscopy sensors, with the capability to resolve InAs nanowire facets, the InAs/GaSb tunnel diode transition and nanoscale defects on the device. We demonstrate that such measurements can rapidly give important insight into the device properties via use of a simplified physical model, without the requirement for extensive calculation of the electrostatics of the system. Interestingly, by precise spatial correlation of the device electrical transport properties and surface structure we show the position and existence of a very abrupt (<10 nm) electrical transition across the InAs/GaSb junction despite the change in material composition occurring only over 30-50 nm. The direct and simultaneous link between nanostructure composition and electrical properties helps set important limits for the precision in structural control needed to achieve desired device performance.

关键词：半导体纳米线半导体器件隧道二极管高分辨率锑化镓砷化铟测量扫描

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An interconnect-free micro-electromechanical 7-bit arithmetic device for multi-operand programmable computing

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Microsystems & Nanoengineering 2023年第2期9卷 355-366页

作者： Xuecui Zou Usman Yaqoob Saly Ahmed Yue Wang Khaled Nabil Salama Hossein Fariborzi CEMSE division King Abdullah University of Science and TechnologyThuwal 23955Saudi Arabia

Computational power density and interconnection between transistors have grown to be the dominant challenges for the continued scaling of complementary metal-oxide-semiconductor(CMOS)technology due to limited integration density and computing ***,we designed a novel,hardware-efficient,interconnect-free microelectromechanical 7:3 compressor using three microbeam *** resonator is configured with seven equal-weighted inputs and multiple driven frequencies,thus defining the transformation rules for transmitting resonance frequency to binary outputs,performing summation operations,and displaying outputs in compact binary *** device achieves low power consumption and excellent switching reliability even after 3 ×10^(3) repeated *** performance improvements,including enhanced computational power capacity and hardware efficiency,are paramount for moderately downscaling ***,our proposed paradigm shift for circuit design provides an attractive alternative to traditional electronic digital computing and paves the way for multioperand programmable computing based on electromechanical systems.

关键词： computing hardware opera

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10 Gbps wavelength division multiplexing using UV-A, UV-B, and UV-C micro-LEDs

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Photonics Research 2022年第2期10卷 516-523页

作者： Daniel M.Maclure Jonathan J.D.McKendry Mohamed Sufyan Islim Enyuan Xie Cheng Chen Xiaobin Sun Xudong Liang Xiaohui Huang Hanaa Abumarshoud Johannes Herrnsdorf Erdan Gu Harald Haas Martin D.Dawson Institute of Photonics Department of PhysicsSUPAUniversity of StrathclydeGlasgow G11RDUK LiFi Research and Development Centre Department of Electronic&Electrical EngineeringUniversity of StrathclydeTechnology&Innovation CentreGlasgow G11RDUK Fraunhofer Center of Applied Photonics Technology&Innovation CentreGlasgow G11RDUK Zhixin semiconductor(Hangzhou)Co. Ltd.Hangzhou 311200China

Deep ultraviolet(DUV) optical wireless communications have seen increased interest in recent years due to the unique properties of light in this spectral region. However, the reported DUV data rates remain significantly lower than comparable demonstrations at visible wavelengths due to lower modulation bandwidths and/or output power of the sources. Here, we present a wavelength division multiplexing demonstration using three UV microlight-emitting diodes emitting at nominal peak wavelengths of 285, 317, and 375 nm, respectively, each with an emitting area of approximately 1369 μm^(2)(equivalent to circular device pixels of diameter;0 μm). Using orthogonal frequency division multiplexing, data rates of 4.17, 3.02, and 3.13 Gbps were achieved from the 285, 317, and 375 nm devices, respectively, for a combined data rate of 10.32 Gbps transmitted over a distance of 0.5 m.

关键词： Gbps multiplexing diodes

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Exciton dynamics in luminescent carbon nanodots： Electron-hole exchange interaction

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Nano Research 2016年第2期9卷 549-559页

作者： Bo Peng Xin Lu Shi Chen Cheng Hon Alfred Huan Qihua Xiong Evren Mutlugun Hilmi Volkan Demir Siu Fung Yu division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 Singapore NOVITAS Nanoelectronics Centre of Excellence School of Electrical and Electronic Engineering Nanyang Technological UniversitySingapore 639798 Singapore LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays School of Electrical and Electronic Engineering NanyangTechnological University Singapore 639798 Singapore Department of Applied Physics the Hong Kong Polytechnic University Hong Hum Hong Kong SAR China

The electron-hole exchange interaction significantly influences the optical properties of excitons and radiative decay. However, exciton dynamics in luminescent carbon dots （Cdots） is still not clear. In this study, we have developed a simple and efficient one-step strategy to synthesize luminescent Cdots using the pyrolysis of oleylamine. The sp^2 clusters of a few aromatic rings are responsible for the observed blue photoluminescence. The size of these clusters can be tuned by controlling the reaction time, and the energy gap between the π-π＊ states of the sp^2 domains decreases as the sp^2 cluster size increases. More importantly, the strong electron-hole exchange interaction results in the splitting of the exciton states of the sp^2 clusters into the singlet-bright and triplet-dark states with an energy difference ΔE, which decreases with increasing sp^2 cluster size owing to the reduction of the confinement energy and the suppression of the electron-hole exchange interaction.

关键词： carbon dots photoluminescence pyrolysis electron-hole exchange interaction energy splitting

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Blue TiO2 polymorph: An efficient material for dye-sensitized solar cells fabricated using a low-temperature sintering process

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Progress in Natural Science:Materials International 2018年第5期28卷 548-553页

作者： Huy Hao Nguyen Gobinda Gyawali Tae Ho Kim Sami Bin Humam Soo Wohn Lee Department of Environmental and Bio-chemical Engineering Sun Moon University division of Basic Engineering Sun Moon University division of Mechanics and ICT Convergence Engineering Sun Moon University

Recently,surface-disordered or non-stoichiometric TiO2,such as blue TiO2(B-TiO2),has received much attention owing to its unique properties,such as structural disorder near the surface and the existence of Ti3+ions and oxygen ***,surface-disordered TiO2has been applied for microwave absorption,photocatalysis,in photoelectrochemical sensors and rechargeable lithium-ion *** this work B-TiO2,a polymorph consisting of nanoparticles,nanotubes and nanosheets,was successfully synthesized and employed as a semiconductor layer in dye-sensitized solar cells(DSSCs)fabricated using a low-temperature heat treatment process(120°C).Based on the analyses of the experimental results regarding the structure and those from the characterization of B-TiO2,and its application to DSSCs,it has been found that the B-TiO2material has an effect on electron-hole pair *** conversion efficiency of the B-TiO2DSSC(BTiO2-DSSC)was 6.18%,whereas that of the TiO2-P25 DSSC(P25-DSSC)was 3.61%,and that of the TiO2polymorph DSSC(PTiO2-DSSC)which is the precursor of B-TiO2was 4.51%.

关键词： Surface-disordered TiO2 Blue TiO2 Dye-sensitized solar cell(DSSC) Oxygen vacancy Efficiency

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Analysis of the local discontinuous Galerkin method for the drift-diffusion model of semiconductor devices

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Science China Mathematics 2016年第1期59卷 115-140页

作者： LIU YunXian SHU Chi-Wang School of Mathematics Shandong University division of Applied Mathematics Brown University

We consider the drift-diffusion(DD) model of one dimensional semiconductor devices, which is a system involving not only first derivative convection terms but also second derivative diffusion terms and a coupled Poisson potential equation. Optimal error estimates are obtained for both the semi-discrete and fully discrete local discontinuous Galerkin(LDG) schemes with smooth solutions. In the fully discrete scheme, we couple the implicit-explicit(IMEX) time discretization with the LDG spatial discretization, in order to allow larger time steps and to save computational cost. The main technical difficulty in the analysis is to treat the inter-element jump terms which arise from the discontinuous nature of the numerical method and the nonlinearity and coupling of the models. A simulation is also performed to validate the analysis.

关键词：漂移扩散模型半导体器件模型有限元分析间断 Galerkin 全离散格式时间离散化最优误差估计

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Improving the Electrical Contact Property of Single-Walled Carbon Nanotube Arrays by Electrodeposition

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Nano-Micro Letters 2013年第4期5卷 242-246页

作者： Min Zhang Advanced Manufacturing division Graduate School at Shenzhen Tsinghua University

A parallel method for the fabrication of metal contacts on single-walled carbon nanotube(SWNT)arrays was presented and the electrical contact property was evaluated by a SWNT-field effect transistor structure. Copper and gold contacts were fabricated on both semiconducting SWNTs and metallic SWNTs by using a maskless electrodeposition process. The SWNT array remained a p-type semiconductor after the electrodeposition. The contact resistance between SWNT array and microelectrodes was reduced more than 50% by the established copper contacts. The source-drain current of the carbon nanotube field-effect transistor(CNT-FET)structure can be further increased from 7.9 μA to 9.2 μA when the copper contacts were replaced by gold ones,which is probably due to the better contact property to SWNT of gold contacts with fine grain size.

关键词： Carbon nanotube Electrodeposition Electrical contact

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On-demand synthesis of high-quality,blue-light-active ZnSe colloidal quantum wires

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National Science Review 2022年第10期9卷 137-146页

作者： Yi Li Chong Zhang Jie Tian Liang Wu Guo-Qiang Liu Hui-Hui Li Yu-Zhuo Zhang Zhen-Chao Shao Zhen He Shu-Hong Yu Department of Chemistry Institute of Biomimetic Materials and Chemistry Anhui Engineering Laboratory of Biomimetic Materials Division of Nanomaterials and Chemistry Hefei National Research Center for Physical Sciences at the Microscale University of Science and Technology of China Engineering and Materials Science Experiment Center University of Science and Technology of China

Beyond the state-of-the-art Cd-containing quantum wires(QWs),heavy-metal-free semiconductor QWs,such as ZnSe,are of great interest for next-generation environmental-benign ***,simultaneous,on-demand manipulation of their radial and axial sizes—that allows strong quantum confinement in the blue-light region—has so far been *** we present a two-step catalyzed growth strategy that enables independent,high-precision and wide-range controls over the diameter and length of ZnSe *** find that a new epitaxial orientation between the cubic-phase Ag2Se solid catalyst and wurtzite ZnSe QWs kinetically favors the formation of defect-free ultrathin *** to their high uniformity,the resulting blue-light-active,phase-pure ZnSe QWs exhibit well-defined excitonic absorption with the 1Se-1Shtransition linewidth as narrow as sub-13 *** the transient absorption spectroscopy,we further show that surface electron traps in these ZnSe QWs can be eliminated by thiol passivation,which results in long-lived charge carriers and high-efficiency solar-to-hydrogen conversion.

关键词： zinc selenide colloidal synthesis quantum wires heavy-metal-free solar conversion

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高速通讯芯片物理实现的工艺选择

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中国集成电路 2002年第4期11卷 62-64页

作者： Michael Bollesen 侯劲松 Cypress semiconductor Director of Strategic Marketing of Datacom division

随着通讯设备速度的不断提高,用来支持这种系统的SERDES(串行变换器和反向串行变换器)设计变得越来越复杂。除了考虑速度要求外,电路设计还必须考虑功耗和兼容性等问题。 OC-48/STM-16是一种光学接口器件,它的版图设计包含了一个光学无... 详细信息

随着通讯设备速度的不断提高,用来支持这种系统的SERDES(串行变换器和反向串行变换器)设计变得越来越复杂。除了考虑速度要求外,电路设计还必须考虑功耗和兼容性等问题。 OC-48/STM-16是一种光学接口器件,它的版图设计包含了一个光学无线收发机、SERDES和SONET/SDH框架。光学无线收发机实现光电转换的功能;

关键词：双极型晶体管工艺选择高速通讯无线收发机放大倍数变换器电路设计芯片设计光学接口压控振荡器

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