| 1. |
- Berg, Alexander, et al.
(författare)
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Growth of wurtzite AlxGa1-xP nanowire shells and characterization by Raman spectroscopy
- 2017
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 28:3
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Tidskriftsartikel (refereegranskat)abstract
- The phonon energies of AlGaP in wurtzite crystal structure are generally not known, as opposed to their zincblende counterparts, because AlGaP crystallizes in zincblende phase in bulk and thin films structures. However, in nanowires AlGaP can be grown in wurtzite crystal structure. In this work we have grown wurtzite GaP/AlGaP/GaP core-shell nanowires by use of MOVPE. After developing suitable growth conditions, the Al composition was determined by STEM-EDX measurements and the wurtzite AlGaP phonon energies by Raman spectroscopy. Raman measurements show a peak shift with increasing Al composition in the AlGaP shell. We find that the phonon energies for wurtzite AlGaP are slightly lower than for zincblende AlGaP. Our results can be used to determine the Al composition in wurtzite AlGaP by Raman scattering.
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| 2. |
- Harfeldt-Berg, Lovisa, et al.
(författare)
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Connecting organizational context to environmental sustainability initiatives and industrial symbiosis : Empirical results and case analysis
- 2023
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Ingår i: Sustainable Production and Consumption. - : Elsevier B.V.. - 2352-5509. ; 40, s. 210-219
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Tidskriftsartikel (refereegranskat)abstract
- Industrial symbiosis can move us closer to a circular economy and enable efficient and sustainable use of resources. Its potential has however been far from realized, and to increase our understanding of why that is, we investigate drivers, barriers, and outcomes associated with both broadly defined environmental sustainability initiatives and industrial symbiosis from an organizational context perspective. A mixed-methods approach is used, combining statistical analysis of survey material with an embedded case study at an industrial symbiosis network in Sotenäs, Sweden. The position of the customer order decoupling point (CODP), a critical aspect of supply chains that separates forecast-based operations from those tied to specific orders, enables comparisons between organizations with primarily forecast-driven operations from those with primarily order-driven operations. We find that the CODP plays an important role in organizations' commitments to sustainability initiatives in general, as organizations with different CODP positions experience different levels of benefits from such initiatives. We did not find that the CODP position had the same impact for industrial symbiosis initiatives. Our results indicate that both industrial symbiosis, a very specific type of sustainability initiative and collaboration, and environmental sustainability initiatives in a broad sense, are associated with multiple, positive business outcomes. However, case study participants also described that their industrial symbiosis participation was time consuming and associated with an added administrative burden. This could be a reason why such collaborations are not more prevalent, despite the potential of bringing about several positive business outcomes. Finally, our findings indicate that industrial symbiosis may bring business-related benefits to firms regardless of their CODP position, but then in order to understand why such networks are not more prevalent, we recommend that future research investigates ways of quantifying and distributing burdens and rewards associated with industrial symbiosis collaboration. © 2023 The Authors
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| 3. |
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| 4. |
- Jain, Vishal, et al.
(författare)
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Bias-dependent spectral tuning in InP nanowire-based photodetectors
- 2017
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Ingår i: Nanotechnology. - Bristol : IOP Publishing. - 0957-4484 .- 1361-6528. ; 28:11
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Tidskriftsartikel (refereegranskat)abstract
- Nanowire array ensembles contacted in a vertical geometry are extensively studied and considered strong candidates for next generations of industrial scale optoelectronics. Key challenges in this development deal with optimization of the doping profile of the nanowires and the interface between nanowires and transparent top contact. Here we report on photodetection characteristics associated with doping profile variations in InP nanowire array photodetectors. Bias-dependent tuning of the spectral shape of the responsivity is observed which is attributed to a Schottky-like contact at the nanowire-ITO interface. Angular dependent responsivity measurements, compared with simulated absorption spectra, support this conclusion. Furthermore, electrical simulations unravel the role of possible self-gating effects in the nanowires induced by the ITO/SiO x wrap-gate geometry. Finally, we discuss possible reasons for the observed low saturation current at large forward biases.
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| 5. |
- Jain, Vishal, et al.
(författare)
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InP/InAsP Nanowire-Based Spatially Separate Absorption and Multiplication Avalanche Photodetectors
- 2017
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Ingår i: ACS Photonics. - Washington : American Chemical Society (ACS). - 2330-4022. ; 4:11, s. 2693-2698
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Tidskriftsartikel (refereegranskat)abstract
- Avalanche photodetectors (APDs) are key components in optical communication systems due to their increased photocurrent gain and short response time as compared to conventional photodetectors. A detector design where the multiplication region is implemented in a large band gap material is desired to avoid detrimental Zener tunneling leakage currents, a concern otherwise in smaller band gap materials required for absorption at 1.3/1.55 μm. Self-assembled III-V semiconductor nanowires offer key advantages such as enhanced absorption due to optical resonance effects, strain-relaxed heterostructures, and compatibility with mainstream silicon technology. Here, we present electrical and optical characteristics of single InP and InP/InAsP nanowire APD structures. Temperature-dependent breakdown characteristics of p+-n-n+ InP nanowire devices were investigated first. A clear trap-induced shift in breakdown voltage was inferred from I-V measurements. An improved contact formation to the p+-InP segment was observed upon annealing, and its effect on breakdown characteristics was investigated. The band gap in the absorption region was subsequently varied from pure InP to InAsP to realize spatially separate absorption and multiplication APDs in heterostructure nanowires. In contrast to the homojunction APDs, no trap-induced shifts were observed for the heterostructure APDs. A gain of 12 was demonstrated for selective optical excitation of the InAsP segment. Additional electron-beam-induced current measurements were carried out to investigate the effect of local excitation along the nanowire on the I-V characteristics. Simulated band profiles and electric field distributions support our interpretation of the experiments. Our results provide important insight for optimization of avalanche photodetector devices based on III-V nanowires.
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| 6. |
- Otnes, Gaute, et al.
(författare)
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Strategies to obtain pattern fidelity in nanowire growth from large-area surfaces patterned using nanoimprint lithography
- 2016
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Ingår i: Nano Research. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 9:10, s. 2852-2861
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Tidskriftsartikel (refereegranskat)abstract
- Position controlled nanowire growth is important for nanowire-based optoelectronic components which rely on light emission or light absorption. For solar energy harvesting applications, dense arrays of nanowires are needed; however, a major obstacle to obtaining dense nanowire arrays is seed particle displacement and coalescing during the annealing stage prior to nanowire growth. Here, we explore three different strategies to improve pattern preservation of large-area catalyst particle arrays defined by nanoimprint lithography for nanowire growth. First, we see that heat treating the growth substrate prior to nanoimprint lithography improves pattern preservation. Second, we explore the possibility of improving pattern preservation by fixing the seed particles in place prior to annealing by modifying the growth procedure. And third, we show that a SiNx growth mask can fully prevent seed particle displacement. We show how these strategies allow us to greatly improve the pattern fidelity of grown InP nanowire arrays with dimensions suitable for solar cell applications, ultimately achieving 100% pattern preservation over the sampled area. The generic nature of these strategies is supported through the synthesis of GaAs and GaP nanowires. [Figure not available: see fulltext.]
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| 7. |
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| 8. |
- Sjöström, Mattias, et al.
(författare)
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A job-exposure matrix for occupational noise : development and validation.
- 2013
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Ingår i: Annals of Occupational Hygiene. - : Oxford University Press (OUP). - 0003-4878 .- 1475-3162. ; 57:6, s. 774-83
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To develop a job-exposure matrix (JEM) for occupational noise in Sweden and to estimate its validity.METHODS: The JEM, developed by a group of experienced occupational hygienists, contains 321 job families with information regarding occupational noise from 1970 to 2004. The occupational noise information derives from measurements collected from different sources. The time period label has a 5-year scale starting in 1970. The estimated average 8h (TWA) noise level in decibel [dB(A)] for every 5-year period was coded either as <75 dB(A), 75-84 dB(A), or ≥85 dB(A) and the risk of peak level exposure assessed. The validity of the JEM is tested, using Svensson's non-parametric methods based on classification consensus, reached by a second group of occupational hygienists.RESULTS/DISCUSSION: Validation results show ~ 80% agreement and no systematic differences, in classification, between the two different groups of occupational hygienists, classifying the occupational noise exposure. However, classification of peak level exposure did show a systematic difference in relative position. The results will give more power to the JEM that it gives a good general estimate for the occupational noise levels in Sweden for different job families during 1970-2004. We, thus, intend to use it in further studies and also make it available to collaborators.
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| 9. |
- Abata, E., et al.
(författare)
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Study of energy response and resolution of the ATLAS barrel calorimeter to hadrons of energies from 20 to 350 GeV
- 2010
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 621:1-3, s. 134-150
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Tidskriftsartikel (refereegranskat)abstract
- A fully instrumented slice of the ATLAS detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. In this paper, the results of the measurements of the response of the barrel calorimeter to hadrons with energies in the range 20-350 GeV and beam impact points and angles corresponding to pseudo-rapidity values in the range 0.2-0.65 are reported. The results are compared to the predictions of a simulation program using the Geant 4 toolkit. (C) 2010 Published by Elsevier B.V.
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| 10. |
- Adalbjörnsson, Stefan, et al.
(författare)
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Conjugate priors for Gaussian emission plsa recommender systems
- 2016
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Ingår i: 2016 24th European Signal Processing Conference, EUSIPCO 2016. - 9780992862657 ; 2016-November, s. 2096-2100
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Konferensbidrag (refereegranskat)abstract
- Collaborative filtering for recommender systems seeks to learn and predict user preferences for a collection of items by identifying similarities between users on the basis of their past interest or interaction with the items in question. In this work, we present a conjugate prior regularized extension of Hofmann's Gaussian emission probabilistic latent semantic analysis model, able to overcome the over-fitting problem restricting the performance of the earlier formulation. Furthermore, in experiments using the EachMovie and MovieLens data sets, it is shown that the proposed regularized model achieves significantly improved prediction accuracy of user preferences as compared to the latent semantic analysis model without priors.
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