| 1. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Chen, X, et al.
(författare)
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Bismuth Effects on Electronic Levels in GaSb(Bi)/AlGaSb Quantum Wells Probed by Infrared Photoreflectance
- 2015
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Ingår i: Chinese Physics Letters. - 0256-307X .- 1741-3540. ; 32:6
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Tidskriftsartikel (refereegranskat)abstract
- GaSb(Bi)/Al0.2Ga0.8Sb single quantum wells are characterized by a Fourier transform infrared spectrometerbased photoreflectance method at 77 K. Spatially direct and indirect transitions between the electronic levels at and above the effective band gap are well resolved. The shifts of the electronic levels with Bi incorporation are identified quantitatively. The results show that the upshift of the valence band edge is clarified to be dominant, while the Bi-induced downshift of the conduction band edge does exist and contributes to the band gap reduction in the GaSbBi quantum-well layer by (29±6)%.
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| 3. |
- Liu, Y., et al.
(författare)
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Bandwidth scaling of phase-modulated CW comb through four-wave mixing on silicon nano-waveguide
- 2013
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Ingår i: 2013 Conference on Lasers and Electro-Optics, CLEO 2013; San Jose, CA; United States; 9 June 2013 through 14 June 2013. - 9781557529725 ; , s. Art. no. 6833039-
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Konferensbidrag (refereegranskat)abstract
- We demonstrate a scheme to scale the bandwidth of a frequency comb generated by phase modulation of CW lasers using four-wave mixing in a silicon nano-waveguides, resulting in >100 comb lines spaced by 10-GHz within 5-dB bandwidth.
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| 4. |
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| 5. |
- Hansson, Josef, 1991, et al.
(författare)
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Bipolar electrochemical capacitors using double-sided carbon nanotubes on graphite electrodes
- 2020
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 451
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Tidskriftsartikel (refereegranskat)abstract
- The electrochemical capacitor (EC) is a key enabler for the miniaturized self-powered systems expected to become ubiquitous with the advent of the internet-of-things (IoT). Vertically aligned carbon nanotubes (VACNTs) on graphite holds promise as electrodes for compact and low-loss ECs. However, as with all ECs, the operating voltage is low, and miniaturization of higher voltage devices necessitates a bipolar design. In this paper, we demonstrate a bipolar EC using graphite/VACNTs electrodes fabricated using a joule heating chemical vapor deposition (CVD) setup. The constructed EC contains one layer of double-sided VACNTs on graphite as bipolar electrode. Compared to a series connection of two individual devices, the bipolar EC has 22% boost in volumetric energy density. More significant boost is envisaged for stacking more bipolar electrode layers. The energy enhancement is achieved without aggravating self-discharge (71.2% retention after 1 h), and at no sacrifice of cycling stability (96.7% over 50000 cycles) owing to uniform growth of VACNTs and thus eliminating cell imbalance problems.
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| 6. |
- Li, G. H., et al.
(författare)
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Surface element segregation and electrical conductivity of lithium layered transition-metal oxide cathode materials
- 2018
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 427, s. 226-232
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Tidskriftsartikel (refereegranskat)abstract
- Surface element segregation and electric conductivity are critical in determining lithium storage ability of given cathode materials, which are poorly understood and not correlated with the structure and overall performance. Here, layered lithium transition-metal oxides, one of the state-of-the-art cathode materials for lithium ion batteries are chosen to study. A serial of LiNixCo1-2xMnxO2 samples were prepared via a solid state reaction and subsequently characterized by XRD in conjunction with structural refinement, XPS depth profiling, and AC impedance spectroscopy. Slightly different expansion rates are observed for lattice parameters (a and c/3) with varying of Ni content, which is attributed to the increase of average metalion radius and an increase of e(g) electron that enhances the columbic repulsion between transition metal and oxygen atoms. XPS depth profiling results show that surface composition is significantly deviated from bulk, in which Ni and Mn atoms tend to enrich in the surface region, while Co element is relatively deficient. Further, surface element segregation is alleviated by the increase of Ni/Mn content. Moreover, increasing the Ni/Mn content also raises the activation energy of bulk conduction.
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| 7. |
- Li, Jia Kai, et al.
(författare)
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Effects of growth conditions on optical quality and surface morphology of InGaAsBi
- 2018
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Ingår i: Chinese Physics B. - : IOP Publishing. - 1674-1056. ; 27:4
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Tidskriftsartikel (refereegranskat)abstract
- The effects of Bi flux and pressure of AsH3 on Bi incorporation, surface morphology and optical properties of In-GaAsBi grown by gas source molecular beam epitaxy are studied. It is found that using relatively low pressure of AsH 3 and high Bi flux can strengthen the effect on the incorporation of Bi and increase its content linearly with Bi flux until it nearly reaches a saturation value. The result from Rutherford backscattering spectroscopy (RBS) confirms that the Bi incorporation can increase up to 1.13%. By adjusting Bi and As flux, we could improve the surface morphology of InGaAsBi sample. Room temperature photoluminescence shows strong and broad light emission at energy levels much smaller than the InGaAs bandgap.
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| 8. |
- Rusydi, A., et al.
(författare)
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Metal-insulator transition in manganites: Changes in optical conductivity up to 22 eV
- 2008
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 78:12, s. 125110 (art. no.)-
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Tidskriftsartikel (refereegranskat)abstract
- The electronic response of doped manganites at the transition from the paramagnetic insulating to the ferromagnetic metallic state in La(1-x)Ca(x)MnO(3) for x=0.3 and 0.2 was investigated by dc conductivity, ellipsometry, and vacuum ultraviolet reflectance for energies between 0 and 22 eV. A stabilized Kramers-Kronig transformation yields the optical conductivity and reveals changes in the optical spectral weight up to 22 eV at the metal-to-insulator transition. In the observed energy range, the spectral weight is conserved within 0.3%. The redistribution of spectral weight in this surprisingly broad energy range has important ramifications for the effective low-energy physics. We discuss the importance of the charge-transfer, Coulomb on-site, Jahn-Teller, and long-range Coulomb screening effects to the electronic structure.
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| 9. |
- Su, F., et al.
(författare)
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Hydrological response to future climate changes for the major upstream river basins in the Tibetan Plateau
- 2016
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 136, s. 82-95
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Tidskriftsartikel (refereegranskat)abstract
- The impacts of future climate change on water balance for the headwater basins of six major rivers in the Tibetan Plateau are assessed using the well-established VIC-glacier land surface hydrological model driven by composite projections of 20 CMIP5 GCMs under scenarios RCP2.6, RCP4.5, and RCP8.5. At the plateau scale, the annual precipitation is projected to increase by 5.0–10.0% in the near term (2011–2040) and 10.0–20.0% in the long term (2041–2070) relative to the reference period 1971–2000. The annual temperature is projected to increase for all the scenarios with the greatest warming in the northwest (2.0–4.0 °C) and least in the southeast (1.2–2.8 °C). The total runoff of the study basins would either remain stable or moderately increase in the near term, and increase by 2.7–22.4% in the long term relative to the reference period, as a result of increased rainfall-induced runoff for the upstream of the Yellow, Yangtze, Salween, and Mekong and increased glacier melt for the upper Indus. In the upper Brahmaputra, more than 50.0% of the total runoff increase is attributed to the increased glacier melt in the long run. The annual hydrograph remains practically unchanged for all the monsoon-dominated basins. However, for the westerly-controlled basin (upper Indus), an apparent earlier melt and a relatively large increase in spring runoff are observed for all the scenarios, which would increase water availability in the Indus Basin irrigation scheme during the spring growing season.
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| 10. |
- Zaidi, A. A., et al.
(författare)
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A Preliminary Study on Waveform Candidates for 5G Mobile Radio Communications Above 6 GHz
- 2016
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Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. ; 2016-July
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Konferensbidrag (refereegranskat)abstract
- This paper provides an overview and preliminary comparison of several multi-carrier and single-carrier waveforms that are potential candidates for future 5G mobile radio communications above 6 GHz. The waveforms are assessed primarily based on the established and known results as well as recent findings keeping in view the design requirements that are relevant to using frequencies above 6 GHz, especially the millimeter wave frequencies. The Key Performance Indicators and degrees of freedom in the design of different waveforms and their potential applications for mm-wave communications are discussed. Certain features that are particularly interesting for mm-wave communication and require further investigations are also highlighted. Furthermore, a common framework for synthesizing different waveform candidates has been developed. Finally, a preliminary qualitative comparison of different multicarrier and single carrier waveforms has been derived.
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