| 1. |
- Breznau, Nate, et al.
(författare)
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Observing many researchers using the same data and hypothesis reveals a hidden universe of uncertainty
- 2022
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 119:44
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Tidskriftsartikel (refereegranskat)abstract
- This study explores how researchers analytical choices affect the reliability of scientific findings. Most discussions of reliability problems in science focus on systematic biases. We broaden the lens to emphasize the idiosyncrasy of conscious and unconscious decisions that researchers make during data analysis. We coordinated 161 researchers in 73 research teams and observed their research decisions as they used the same data to independently test the same prominent social science hypothesis: that greater immigration reduces support for social policies among the public. In this typical case of social science research, research teams reported both widely diverging numerical findings and substantive conclusions despite identical start conditions. Researchers expertise, prior beliefs, and expectations barely predict the wide variation in research outcomes. More than 95% of the total variance in numerical results remains unexplained even after qualitative coding of all identifiable decisions in each teams workflow. This reveals a universe of uncertainty that remains hidden when considering a single study in isolation. The idiosyncratic nature of how researchers results and conclusions varied is a previously underappreciated explanation for why many scientific hypotheses remain contested. These results call for greater epistemic humility and clarity in reporting scientific findings.
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| 2. |
- Eliasson, H., et al.
(författare)
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Modeling of high power impulse magnetron sputtering discharges with graphite target
- 2021
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Ingår i: Plasma sources science & technology. - : IOP Publishing Ltd. - 0963-0252 .- 1361-6595. ; 30:11
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Tidskriftsartikel (refereegranskat)abstract
- The ionization region model (IRM) is applied to model a high power impulse magnetron sputtering discharge in argon with a graphite target. Using the IRM, the temporal variation of the various species and the average electron energy, as well as internal parameters such as the ionization probability, back-attraction probability, and the ionized flux fraction of the sputtered species, is determined. It is found that thedischarge develops into working gas recycling and most of the discharge current at the cathode target surface is composed of Ar+ ions, which constitute over 90% of the discharge current, while the contribution of the C+ ions is always small (<5%), even for peak current densities close to 3 A cm(-2). For the target species, the time-averaged ionization probability is low, or 13-27%, the ion back-attraction probability during the pulse is high (>92%), and the ionized flux fraction is about 2%. It is concluded that in the operation range studied here it is a challenge to ionize carbon atoms, that are sputtered off of a graphite target in a magnetron sputtering discharge, when depositing amorphous carbon films.
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| 3. |
- Christian Roelofs, W. S., et al.
(författare)
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Light Emission in the Unipolar Regime of Ambipolar Organic Field-Effect Transistors
- 2013
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Ingår i: Advanced Functional Materials. - : Wiley-VCH Verlag. - 1616-301X .- 1616-3028. ; 23:33, s. 4133-4139
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Tidskriftsartikel (refereegranskat)abstract
- Light emission from ambipolar organic field-effect transistors (OFETs) is often observed when they are operated in the unipolar regime. This is unexpected, the light emission should be completely suppressed, because in the unipolar regime only one type of charge carrier is accumulated. Here, an electroluminescent diketopyrrolopyrrole copolymer is investigated. Local potential measurements by scanning Kelvin probe microscopy reveal a recombination position that is unstable in time due to the presence of injection barriers. The electroluminescence and electrical transport have been numerically analyzed. It is shown that the counterintuitive unipolar light emission is quantitatively explained by injection of minority carriers into deep tail states of the semiconductor. The density of the injected minority carriers is small. Hence they are relatively immobile and they recombine close the contact with accumulated majority carriers. The unipolar light output is characterized by a constant efficiency independent of gate bias. It is argued that light emission from OFETs predominantly originates from the unipolar regime when the charge transport is injection limited.
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| 4. |
- Germs, W. Chr., et al.
(författare)
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Charge transport in amorphous InGaZnO thin-film transistors
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 86:15
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the mechanism of charge transport in indium gallium zinc oxide (a-IGZO), an amorphous metal-oxide semiconductor. We measured the field-effect mobility and the Seebeck coefficient (S = Delta V/Delta T) of a-IGZO in thin-film transistors as a function of charge-carrier density for different temperatures. Using these transistors, we further employed a scanning Kelvin probe-based technique to determine the density of states of a-IGZO that is used as the basis for the modeling. After comparing two commonly used models, the band transport percolation model and a mobility edge model, we find that both cannot describe the full properties of the charge transport in the a-IGZO semiconductor. We, therefore, propose a model that extends the mobility edge model to allow for variable range hopping below the mobility edge. The extended mobility edge model gives a superior description of the experimental results. We show that the charge transport is dominated by variable range hopping below, rather than by bandlike transport above the mobility edge.
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