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702 results on '"Wetzel, C."'

4. Ultrasensitive tunability of the direct bandgap of 2D InSe flakes via strain engineering

Author

Li, Y, Wang, T, Wu, M, Cao, T, Chen, Y, Sankar, R, Ulaganathan, RK, Chou, F, Wetzel, C, Xu, CY, Louie, SG, and Shi, SF

Subjects
2D materials, flexible optoelectronics, strain, band structure engineering, InSe, Macromolecular and Materials Chemistry, Materials Engineering, Nanotechnology
Abstract

InSe, a member of the layered materials family, is a superior electronic and optical material which retains a direct bandgap feature from the bulk to atomically thin few-layers and high electronic mobility down to a single layer limit. We, for the first time, exploit strain to drastically modify the bandgap of two-dimensional (2D) InSe nanoflakes. We demonstrated that we could decrease the bandgap of a few-layer InSe flake by 160 meV through applying an in-plane uniaxial tensile strain to 1.06% and increase the bandgap by 79 meV through applying an in-plane uniaxial compressive strain to 0.62%, as evidenced by photoluminescence (PL) spectroscopy. The large reversible bandgap change of ∼239 meV arises from a large bandgap change rate (bandgap strain coefficient) of few-layer InSe in response to strain, ∼154 meV/% for uniaxial tensile strain and ∼140 meV/% for uniaxial compressive strain, representing the most pronounced uniaxial strain-induced bandgap strain coefficient experimentally reported in 2D materials. We developed a theoretical understanding of the strain-induced bandgap change through first-principles DFT and GW calculations. We also confirmed the bandgap change by photoconductivity measurements using excitation light with different photon energies. The highly tunable bandgap of InSe in the infrared regime should enable a wide range of applications, including electro-mechanical, piezoelectric and optoelectronic devices.

Published
2018

5. On Complementing the Tracer Toolbox for Quantifying Hydrological Connectivity: Insights Gained from Terrestrial Diatom Tracer Experiments

Author

Pfister, L., Allen, S. T., Wetzel, C. E., Martínez-Carreras, N., Canadell, Josep G., Series Editor, Díaz, Sandra, Series Editor, Heldmaier, Gerhard, Series Editor, Jackson, Robert B., Series Editor, Levia, Delphis F., Series Editor, Schulze, Ernst-Detlef, Series Editor, Sommer, Ulrich, Series Editor, Wardle, David A., Series Editor, Carlyle-Moses, Darryl E., editor, Iida, Shin'ichi, editor, Michalzik, Beate, editor, Nanko, Kazuki, editor, and Tischer, Alexander, editor

Published
2020
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16. Carrier Localization in Gallium Nitride

Author

Wetzel, C., Walukiewicz, W., Haller, E.E., Ager, J.W., Chen, T., Fischer, S., Yu, P., Jeanloz, R., Grzegory, I., Porowski, S., Suski, T., Amano, H., and Akasaki, I.

Published
1996

21. Prognostische Wertigkeit der TSPO-PET bei Patienten mit Gliomrezidiv

Author

Quach, S., additional, Holzgreve, A., additional, Kaiser, L., additional, Dekorsy, F.J., additional, Unterrainer, M., additional, Bartos, L.M., additional, Ruf, V.C., additional, Wetzel, C., additional, Herms, J., additional, Riemenschneider, M.J., additional, Rupprecht, R., additional, Brendel, M., additional, Thon, N., additional, von Baumgarten, L., additional, Bartenstein, P., additional, Tonn, J.C., additional, and Albert, N.L., additional

Published
2022
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25. Instructional Effectiveness of Video Media.

Author

Wetzel, C. Douglas and Wetzel, C. Douglas

Abstract

This volume is a blend of media research, cognitive science research, and tradecraft knowledge regarding video production techniques. The research covers: visual learning; verbal-auditory information; news broadcasts; the value of motion and animation in film and video; simulation (including realism and fidelity); the relationship of text and graphics; computer-based learning using video and animated graphics; the role of effort in learning from media; and the concept of media symbol systems. When available, results from various meta-analysis are also reviewed. Media systems are discussed in terms of instructional effectiveness and cost benefits. Media systems include educational television, distance learning, and teacher education. Many of the benefits of video are practical ones, for example, convenience, access, standardization, and efficiency. Chapters include: "Forms of Educational Television"; "Processing Visual and Verbal Information"; "Dynamic Visual Presentations"; "Computer-Based Interactive Video"; "Video Production Methods and Tradecraft"; "Production Methods and Learning"; "Learning, Mental Effort, and the Perception of Media"; "Symbol Systems and Media"; and "Perspectives on Video Media." (Contains over 500 references.) (MAS)

Published
1994

26. Generative Aspects of the Computer Based Educational Software System (CBESS).

Author

Wetzel, C. Douglas

Abstract

Discussion of authoring tools for computer-based instruction (CBI) focuses on the Computer-Based Educational Software System developed for Navy training. Topics addressed include user experience and task difficulty; generative CBI techniques for memorization and technical vocabulary training; generating questions from a semantic network; and the impact of increased flexibility. (27 references) (LRW)

Published
1993

32. Boosting green GaInN/GaN light-emitting diode performance by a GaInN underlying layer

Author

Yong Xia, Wenting Hou, Liang Zhao, Mingwei Zhu, Detchprohm, T., and Wetzel, C.

Subjects
Gallium compounds -- Electric properties, Gallium nitrate -- Electric properties, Light-emitting diodes -- Innovations, Quantum wells -- Usage, Simulation methods -- Usage, Voltage -- Measurement, Business, Electronics, Electronics and electrical industries
Published
2010

36. Radiation effects on InGaN quantum wells and GaN simultaneously probed by ion beam-induced luminescence

Author

Tringe, J.W., Conway, A.M., Felter, T.E., Chan, W.J. Moberly, Castelaz, J., Lordi, V., Xia, Y., Stevens, C.G., and Wetzel, C.

Subjects
Light-emitting diodes -- Analysis, Business, Electronics, Electronics and electrical industries
Abstract

InGaN quantum well structures on GaN epilayers were exposed to 500 keV alpha particles to fluences above [10.sup.14] [cm.sup.2] to probe the relative radiation tolerance of the epilayer and wells. Performance was estimated by the intensity of ion-beam induced luminescence. Two separate types of quantum well structures emitted at 470 and 510 nm prior to irradiation, and only small wavelength shifts were observed even with the highest alpha fluences. Complementary cathodoluminescence experiments showed that luminescence in the quantum wells is strongly influenced by charges injected deep into the GaN epilayer. The 500 keV alpha penetration depth was ~1 [micro]m, so that defects were created at a faster rate in GaN compared to InGaN as alpha particles slowed and stopped within a minority carrier diffusion length of the quantum wells. However, the rate of luminescent decay was similar for both materials. Taken together with the cathodoluminescence data, this ion-beam induced luminescence comparison indicates that the quantum well luminescence decay rate is dominated by radiation-induced defects in the GaN epilayer. InGaN quantum wells are then demonstrated to be not more than a factor of ten more radiation sensitive than GaN, and may be substantially less sensitive than this upper bound. Index Terms--Alpha particle, InGaN, light-emitting diode, quantum well, radiation.

Published
2008

43. Nitride-based laser diodes using thick n-AlGaN layers

Author

Takeuchi, T., Detchprohm, T., Iwaya, M., Hayashi, N., Isomura, K., Kimura, K., Yamaguchi, M., Yamaguchi, S., Wetzel, C., Amano, H., Akasaki, I., Kaneko, Y. W., Shioda, R., Watanabe, S., Hidaka, T., Yamaoka, Y., Kaneko, Y. S., and Yamada, N.

Published
2000
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46. Piezoelectric Franz-Keldysh effect in strained GaInN/GaN heterostructures

Author

Wetzel, C., Takeuchi, T., Amano, H., and Akasaki, I.

Subjects
Semiconductors -- Optical properties, Piezoelectricity -- Research, Physics
Abstract

Research was conducted to examine the pseudomorphic Ga(sub 1-x)In(sub x)N/GaN single heterostructures in the composition range 0

Published
1999

50. Flow-regulated versus differential pressure shunt valves for treatment of idiopathic normal pressure hydrocephalus

Author

Görtz, L, Schulte, AP, Noé, P, Goldbrunner, R, Krischek, B, and Wetzel, C

Subjects
ddc: 610, 610 Medical sciences, Medicine
Abstract

Objective: Overdrainage and frequent reprogramming are common issues with programmable differential pressure (DP) valves after ventriculoperitoneal shunt surgery for idiopathic normal pressure hydrocephalus (iNPH). Non-programmable, flow-regulated (FR) valves may address these limitations, however, [for full text, please go to the a.m. URL], 70. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit der Skandinavischen Gesellschaft für Neurochirurgie

Published
2019
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