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  • 1
    Publication Date: 2015-11-28
    Description: Two-dimensional (2D) transition metal dichalcogenides have emerged as a promising material system for optoelectronic applications, but their primary figure of merit, the room-temperature photoluminescence quantum yield (QY), is extremely low. The prototypical 2D material molybdenum disulfide (MoS2) is reported to have a maximum QY of 0.6%, which indicates a considerable defect density. Here we report on an air-stable, solution-based chemical treatment by an organic superacid, which uniformly enhances the photoluminescence and minority carrier lifetime of MoS2 monolayers by more than two orders of magnitude. The treatment eliminates defect-mediated nonradiative recombination, thus resulting in a final QY of more than 95%, with a longest-observed lifetime of 10.8 +/- 0.6 nanoseconds. Our ability to obtain optoelectronic monolayers with near-perfect properties opens the door for the development of highly efficient light-emitting diodes, lasers, and solar cells based on 2D materials.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Amani, Matin -- Lien, Der-Hsien -- Kiriya, Daisuke -- Xiao, Jun -- Azcatl, Angelica -- Noh, Jiyoung -- Madhvapathy, Surabhi R -- Addou, Rafik -- KC, Santosh -- Dubey, Madan -- Cho, Kyeongjae -- Wallace, Robert M -- Lee, Si-Chen -- He, Jr-Hau -- Ager, Joel W 3rd -- Zhang, Xiang -- Yablonovitch, Eli -- Javey, Ali -- New York, N.Y. -- Science. 2015 Nov 27;350(6264):1065-8. doi: 10.1126/science.aad2114.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA 94720, USA. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. ; Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA 94720, USA. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia. Department of Electrical Engineering, Institute of Electronics Engineering, National Taiwan University, Taipei 10617, Taiwan, Republic of China. ; National Science Foundation Nanoscale Science and Engineering Center, University of California, Berkeley, Berkeley, CA 94720, USA. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. ; Department of Materials Science and Engineering, University of Texas, Dallas, Richardson, TX 75080, USA. ; Sensors and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, MD 20723, USA. ; Department of Electrical Engineering, Institute of Electronics Engineering, National Taiwan University, Taipei 10617, Taiwan, Republic of China. ; Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia. ; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. ; National Science Foundation Nanoscale Science and Engineering Center, University of California, Berkeley, Berkeley, CA 94720, USA. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. Department of Physics, King Abdulaziz University, Jeddah 21589, Saudi Arabia. ; Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA 94720, USA. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. ajavey@eecs.berkeley.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26612948" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2016-01-29
    Description: Wearable sensor technologies are essential to the realization of personalized medicine through continuously monitoring an individual's state of health. Sampling human sweat, which is rich in physiological information, could enable non-invasive monitoring. Previously reported sweat-based and other non-invasive biosensors either can only monitor a single analyte at a time or lack on-site signal processing circuitry and sensor calibration mechanisms for accurate analysis of the physiological state. Given the complexity of sweat secretion, simultaneous and multiplexed screening of target biomarkers is critical and requires full system integration to ensure the accuracy of measurements. Here we present a mechanically flexible and fully integrated (that is, no external analysis is needed) sensor array for multiplexed in situ perspiration analysis, which simultaneously and selectively measures sweat metabolites (such as glucose and lactate) and electrolytes (such as sodium and potassium ions), as well as the skin temperature (to calibrate the response of the sensors). Our work bridges the technological gap between signal transduction, conditioning (amplification and filtering), processing and wireless transmission in wearable biosensors by merging plastic-based sensors that interface with the skin with silicon integrated circuits consolidated on a flexible circuit board for complex signal processing. This application could not have been realized using either of these technologies alone owing to their respective inherent limitations. The wearable system is used to measure the detailed sweat profile of human subjects engaged in prolonged indoor and outdoor physical activities, and to make a real-time assessment of the physiological state of the subjects. This platform enables a wide range of personalized diagnostic and physiological monitoring applications.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gao, Wei -- Emaminejad, Sam -- Nyein, Hnin Yin Yin -- Challa, Samyuktha -- Chen, Kevin -- Peck, Austin -- Fahad, Hossain M -- Ota, Hiroki -- Shiraki, Hiroshi -- Kiriya, Daisuke -- Lien, Der-Hsien -- Brooks, George A -- Davis, Ronald W -- Javey, Ali -- P01 HG000205/HG/NHGRI NIH HHS/ -- England -- Nature. 2016 Jan 28;529(7587):509-14. doi: 10.1038/nature16521.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, USA. ; Berkeley Sensor and Actuator Center, University of California, Berkeley, California 94720, USA. ; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA. ; Stanford Genome Technology Center, Stanford School of Medicine, Palo Alto, California 94304, USA. ; Integrative Biology, University of California, Berkeley, California 94720, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26819044" target="_blank"〉PubMed〈/a〉
    Keywords: Adult ; Bicycling/physiology ; Body Water ; Calibration ; Electrolytes/analysis ; Female ; Glucose/analysis ; Healthy Volunteers ; Humans ; Lactic Acid/analysis ; Male ; Monitoring, Physiologic/*instrumentation/*methods ; Precision Medicine/instrumentation/methods ; Reproducibility of Results ; Running/physiology ; Skin ; Skin Temperature ; Sweat/*chemistry ; Young Adult
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2006-07-24
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 4
    Publication Date: 2019
    Description: 〈p〉In recent years, there have been tremendous advancements in the growth of monolayer transition metal dichalcogenides (TMDCs) by chemical vapor deposition (CVD). However, obtaining high photoluminescence quantum yield (PL QY), which is the key figure of merit for optoelectronics, is still challenging in the grown monolayers. Specifically, the as-grown monolayers often exhibit lower PL QY than their mechanically exfoliated counterparts. In this work, we demonstrate synthetic tungsten diselenide (WSe〈sub〉2〈/sub〉) monolayers with PL QY exceeding that of exfoliated crystals by over an order of magnitude. PL QY of ~60% is obtained in monolayer films grown by CVD, which is the highest reported value to date for WSe〈sub〉2〈/sub〉 prepared by any technique. The high optoelectronic quality is enabled by the combination of optimizing growth conditions via tuning the halide promoter ratio, and introducing a simple substrate decoupling method via solvent evaporation, which also mechanically relaxes the grown films. The achievement of scalable WSe〈sub〉2〈/sub〉 with high PL QY could potentially enable the emergence of technologically relevant devices at the atomically thin limit.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 5
    Publication Date: 2019
    Description: 〈p〉Defects in conventional semiconductors substantially lower the photoluminescence (PL) quantum yield (QY), a key metric of optoelectronic performance that directly dictates the maximum device efficiency. Two-dimensional transition-metal dichalcogenides (TMDCs), such as monolayer MoS〈sub〉2〈/sub〉, often exhibit low PL QY for as-processed samples, which has typically been attributed to a large native defect density. We show that the PL QY of as-processed MoS〈sub〉2〈/sub〉 and WS〈sub〉2〈/sub〉 monolayers reaches near-unity when they are made intrinsic through electrostatic doping, without any chemical passivation. Surprisingly, neutral exciton recombination is entirely radiative even in the presence of a high native defect density. This finding enables TMDC monolayers for optoelectronic device applications as the stringent requirement of low defect density is eased.〈/p〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
    Publication Date: 2015-11-26
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
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