| 1. |
- Jacobsson, Jesper, 1984-, et al.
(författare)
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An open-access database and analysis tool for perovskite solar cells based on the FAIR data principles
- 2022
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Ingår i: Nature Energy. - : Springer Nature. - 2058-7546. ; 7:1, s. 107-115
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Tidskriftsartikel (refereegranskat)abstract
- Large datasets are now ubiquitous as technology enables higher-throughput experiments, but rarely can a research field truly benefit from the research data generated due to inconsistent formatting, undocumented storage or improper dissemination. Here we extract all the meaningful device data from peer-reviewed papers on metal-halide perovskite solar cells published so far and make them available in a database. We collect data from over 42,400 photovoltaic devices with up to 100 parameters per device. We then develop open-source and accessible procedures to analyse the data, providing examples of insights that can be gleaned from the analysis of a large dataset. The database, graphics and analysis tools are made available to the community and will continue to evolve as an open-source initiative. This approach of extensively capturing the progress of an entire field, including sorting, interactive exploration and graphical representation of the data, will be applicable to many fields in materials science, engineering and biosciences.
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| 2. |
- Dammann, M., et al.
(författare)
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Reliability and degradation mechanism of AlGaN/GaN HEMTs for next generation mobile communication systems
- 2009
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Ingår i: Microelectronics and Reliability. - : Elsevier BV. - 0026-2714. ; 49:5, s. 474-477
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Tidskriftsartikel (refereegranskat)abstract
- Excellent reliability performance of AlGaN/GaN HEMTs on SiC substrates for next generation mobile communication systems has been demonstrated using DC and RF stress tests on 8 x 60 mu m wide and 0.5 mu m long AlGaN/GaN HEMTs at a drain voltage of V-d = 50 V. Drain current recovery measurements after stress indicate that the degradation is partly caused by slow traps generated in the SiN passivation or in the HEMT epitaxial layers. The traps in the SiN passivation layer were characterized using high and low frequency capacitance-voltage (CV) measurements of MIS test structures on thick lightly doped GaN layers. (C) 2009 Elsevier Ltd. All rights reserved.
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| 3. |
- Hanifpour, Fatemeh, et al.
(författare)
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Investigation into the mechanism of electrochemical nitrogen reduction reaction to ammonia using niobium oxynitride thin-film catalysts
- 2022
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 403
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Tidskriftsartikel (refereegranskat)abstract
- Niobium oxynitride (NbOxNy) thin films with varying combined non-metal vs. metal stoichiometries ( x + y ) and N/O stoichiometric ratios (y/x) are investigated for their ability to catalyze the nitrogen re-duction reaction and ammonia synthesis at ambient conditions. Electrochemical impedance spectroscopy and ammonia measurements show stark differences both in nitrogen vs. argon media on each surface and on the surfaces in the series when the combined stoichiometry of N + O vs. Nb increases. Surface stability checks at fixed intervals during the experiments and surface characterization after the experiments us -ing X-ray diffraction reveal the least changes occurred to the surface with the highest N + O stoichiometry. Based on these observations, an ammonia synthesis mechanism is proposed. Isotope labeling experiments on the most promising surface of the series, however, show no sign of catalytically produced ammonia, possibly due to the lack of stability of the surface to endure through the ammonia production cycle.
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| 4. |
- Hanifpour, Fatemeh, et al.
(författare)
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Operando quantification of ammonia produced from computationally-derived transition metal nitride electro-catalysts
- 2022
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Ingår i: Journal of Catalysis. - : Elsevier. - 0021-9517 .- 1090-2694. ; 413, s. 956-967
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical reduction of dinitrogen to ammonia is investigated in a micro-reactor flow-cell using thin films of VN, CrN, NbN and ZrN. Chronoamperometry loops are used for ammonia production analysis. Operando ammonia quantification is accomplished in a flow injection analyzer. Results show the effect of presence/absence of N-2(g) within both the electrochemical characterization and ammonia production for ZrN. However, no ammonia is detected from studies on CrN. VN and NbN are inactivated upon reacting their N atoms of the surface top layer(s). Results obtained from ammonia measurements, electrochemical impedance spectroscopy analysis, surface stability checks, and surface characterization using X-ray reflectivity, reveal certain trends indicating catalytic behavior for ZrN. However, the concentration of produced ammonia is below the detection limit of the methods devised to analyze the samples from isotope labeling experiments. The onset of ammonia production on ZrN appears to be in close agreement with that predicted previously by computational studies.
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| 5. |
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| 6. |
- Khosa, Rabia Y., et al.
(författare)
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Electrical characterization of high k-dielectrics for 4H-SiC MIS devices
- 2019
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Ingår i: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 98, s. 55-58
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Tidskriftsartikel (refereegranskat)abstract
- We report promising results regarding the possible use of AlN or Al 2 O 3 as a gate dielectric in 4H-SiC MISFETs. The crystalline AlN films are grown by hot wall metal organic chemical vapor deposition (MOCVD) at 1100 °C. The amorphous Al 2 O 3 films are grown by repeated deposition and subsequent low temperature (200 °C) oxidation of thin Al layers using a hot plate. Our investigation shows a very low density of interface traps at the AlN/4H-SiC and the Al 2 O 3 /4H-SiC interface estimated from capacitance-voltage (CV) analysis of MIS capacitors. Current-voltage (IV) analysis shows that the breakdown electric field across the AlN or Al 2 O 3 is ∼ 3 MV/cm or ∼ 5 MV/cm respectively. By depositing an additional SiO 2 layer by plasma enhanced chemical vapor deposition at 300 °C on top of the AlN or Al 2 O 3 layers, it is possible to increase the breakdown voltage of the MIS capacitors significantly without having pronounced impact on the quality of the AlN/SiC or Al 2 O 3 /SiC interfaces.
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| 7. |
- Khosa, Rabia Y., et al.
(författare)
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Electrical characterization of MOCVD grown single crystalline ALN thin films on 4H-SiC
- 2019
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Ingår i: Materials Science Forum. - : Trans Tech Publications Ltd. - 1662-9752 .- 0255-5476. ; 963 MSF, s. 460-464, s. 460-464
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Konferensbidrag (refereegranskat)abstract
- We report on a very low density of interface traps at the AlN/4H-SiC interface estimated from capacitance-voltage (CV) analysis of metal-insulator-semiconductor (MIS) capacitors. Single crystalline aluminum nitride (AlN) films are grown by metal organic chemical vapor deposition (MOCVD). Current-voltage (IV) analysis shows that the breakdown electric field across the AlN dielectric is 3 MV/cm. By depositing an additional SiO2 layer on top of the AlN layer it is possible to increase the breakdown voltage of the MIS capacitors significantly without having pronounced impact on the quality of the AlN/SiC interface.
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| 8. |
- Khosa, Rabia Y., et al.
(författare)
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Electrical properties of 4H-SiC MIS capacitors with AlN gate dielectric grown by MOCVD
- 2019
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Ingår i: Solid-State Electronics. - : Elsevier BV. - 0038-1101 .- 1879-2405. ; 153, s. 52-58
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Tidskriftsartikel (refereegranskat)abstract
- We report on the electrical properties of the AlN/4H-SiC interface using capacitance- and conductance-voltage (CV and GV) analysis of AlN/SiC MIS capacitors. The crystalline AlN layers are made by hot wall MOCVD. CV analysis at room temperature reveals an order of magnitude lower density of interface traps at the AlN/SiC interface than at nitrided SiO2/SiC interfaces. Electron trapping in bulk traps within the AlN is significant when the MIS capacitors are biased into accumulation resulting in a large flatband voltage shift towards higher gate voltage. This process is reversible and the electrons are fully released from the AlN layer if depletion bias is applied at elevated temperatures. Current-voltage (IV) analysis reveals that the breakdown electric field intensity across the AlN dielectric is 3–4 MV/cm and is limited by trap assisted leakage. By depositing an additional SiO2 layer on top of the AlN layer, it is possible to increase the breakdown voltage of the MIS capacitors significantly without having much impact on the quality of the AlN/SiC interface.
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| 9. |
- Sigmundsson, F., et al.
(författare)
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Intrusion triggering of the 2010 Eyjafjallajökull explosive eruption
- 2010
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Ingår i: Nature. ; 468:7322, s. 426-430
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Tidskriftsartikel (refereegranskat)abstract
- Gradual inflation of magma chambers often precedes eruptions at highly active volcanoes. During such eruptions, rapid deflation occurs as magma flows out and pressure is reduced1–3. Less is known about the deformation style at moderately active volcanoes, such as Eyjafjallajo¨kull, Iceland, where an explosive summit eruption of trachyandesite beginning on 14 April 2010 caused exceptional disruption to air traffic, closing airspace over much of Europe for days. This eruption was preceded by an effusive flank eruption of basalt from 20 March to 12 April 2010. The 2010 eruptions are the culmination of 18 years of intermittent volcanic unrest4–9. Here we show that deformation associated with the eruptions was unusual because it did not relate to pressure changes within a single magma chamber. Deformation was rapid before the first eruption (.5mm per day after 4 March), but negligible during it. Lack of distinct co-eruptive deflation indicates that the net volume of magma drained from shallow depth during this eruption was small; rather, magma flowed from considerable depth. Before the eruption, a 0.05km3 magmatic intrusion grew over a period of three months, in a temporally and spatially complex manner, as revealed by GPS (Global Positioning System) geodetic measurements and interferometric analysis of satellite radar images. The second eruption occurred within the ice-capped caldera of the volcano, with explosivity amplified by magma–ice interaction. Gradual contraction of a source, distinct from the pre-eruptive inflation sources, is evident from geodetic data. Eyjafjallajo¨kull’s behaviour can be attributed to its off-rift setting with a ‘cold’ subsurface structure and limited magma at shallow depth, as may be typical for moderately active volcanoes. Clear signs of volcanic unrest signals over years to weeks may indicate reawakening of such volcanoes, whereas immediate short-term eruption precursors may be subtle and difficult to detect.
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| 10. |
- Tilak, V., et al.
(författare)
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Scattering Mechanisms in Silicon Carbide MOSFETs with Gate Oxides Fabricated using Sodium Enhanced Oxidation Technique
- 2009
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Ingår i: Materials Science Forum. - : Trans Tech Publications, Ltd.. - 1662-9752 .- 0255-5476. - 9780878493579 ; 600-603, s. 687-690
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Konferensbidrag (refereegranskat)abstract
- The improvement of the SiC-SiO(2) interface has been the main focus of research in SiC MOSFET technology due to the presence of high density of interface traps (D(it)) leading to poor threshold voltage temperature stability and poor mobility. In SiC MOSFETs with the gate oxide grown in the presence of sodium, known as sodium enhanced oxidation(SEO), a lower Dit and higher field effect mobility has been observed [1]. Hall effect measurements were performed from 125 degrees K-225 degrees K on such MOSFET samples. The Hall measurements were made as a function of temperature for various sheet charge concentrations. The sheet charge density was measured as a function of gate bias at 225 degrees K and there is very little trapped charge in the sample with oxide grown by SEO while about 50% of the total charge is trapped in a sample with N(2)O grown oxide annealed in NO. In samples with oxide grown by SEO, there is a monotonic increase in mobility with sheet charge density and the mobility also increases with temperature. This is an indication that the main scattering mechanism is Coulomb scattering in this regime.
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