| 1. |
- Afrasiabi, Roodabeh, et al.
(författare)
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Microwave mediated synthesis of semiconductor quantum dots
- 2012
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Ingår i: Physica Status Solidi. C, Current topics in solid state physics. - : Wiley. - 1610-1634 .- 1610-1642. ; 9:7, s. 1551-1556
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Tidskriftsartikel (refereegranskat)abstract
- Colloidal quantum dots (QD) have tuneable optoelectronic properties and can be easily handled by simple solution processing techniques, making them very attractive for a wide range of applications. Over the past decade synthesis of morphology controlled high quality (crystalline, monodisperse) colloidal QDs by thermal decomposition of organometallic precursors has matured and is well studied. Recently, synthesis of colloidal QDs by microwave irradiation as heating source is being studied due to the inherently different mechanisms of heat transfer, when compared to solvent convection based heating. Under microwave irradiation, polar precursor molecules directly absorb the microwave energy and heat up more efficiently. Here we report synthesis of colloidal II-VI semiconductor QDs (CdS, CdSe, CdTe) by microwave irradiation and compare it with conventional synthesis based on convection heating. Our findings show that QD synthesis by microwave heating is more efficient and the chalcogenide precursor strongly absorbs the microwave radiation shortening the reaction time and giving a high reaction yield.
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| 2. |
- Aggerstam, Thomas, et al.
(författare)
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AlGaN/GaN high-electron-mobility transistors on sapphire with Fe-doped GaN buffer layer by MOVPE
- 2006
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Ingår i: Physica Status Solidi C - Current Topics in Solid State Physics. - : Wiley. ; , s. 2373-2376
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Konferensbidrag (refereegranskat)abstract
- A simple AlGaN/GaN HEMT structure without any interlayer on Fe-doped GaN (GaN:Fe) grown by LP-MOVPE in one single run on sapphire is demonstrated. The surface segregation of Fe in GaN occurring during growth is identified. Hall measurements yield 2DEG (two dimensional electron gas) mobilities of 1700 and 10700 cm2/Vs and sheet carrier concentrations of 5.1×10 12 and 5.7×1012 cm-2 at 300 K and 20 K, respectively. Good pinch-off current-voltage (ID-VD) characteristics is observed from AlGaN/GaN HEMTs. A maximum drain current density of 0.6 A/mm and a peak extrinsic transconductance of 200 mS/mm have been observed. The HEMT structure yields very good device isolation as indicated by an isolation current of ≀1 nA at 20 V.
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| 3. |
- Aiboushev, A. V., et al.
(författare)
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Enhanced luminescence and two-photon absorption of silver nano-clusters
- 2009
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Ingår i: Physica Status Solidi c. - : Wiley. - 1862-6351 .- 1610-1642. ; 6:0, s. S162-S166
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Tidskriftsartikel (refereegranskat)abstract
- Luminescence of silver nanoparticles photo-deposited on titan dioxide nanoparticles of mesoporous film is studied. Luminescence was registered under the two-photon excitation by femto-second laser pulses of Ti:sapphire laser. It was observed that Ag/ TiO2 mesoporous films have high concentration of bright luminescence spots which reveal stability to degradation under long illumination. Various configurations of silver nanoparticles are analyzed to explain the physics of bright luminescence spots ( hot spots). Luminescence intensity reveals hot spots dependence on the polarization of excitation laser pulse. Properties of Ag/TiO2 system can be useful for single molecule spectroscopy and visualization of biological objects. Aapplication of Ag/ TiO2 mesoporous films for Raman scattering spectroscopy de-menstruated for the case of Rhodamine B.
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| 4. |
- Arwin, Hans, 1950-, et al.
(författare)
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Infrared ellipsometry studies of thermal stability of protein monolayers and multilayers
- 2008
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Ingår i: Physica Status Solidi. C: Current Topics in Solid State Physics. - Weinheim, Germany : Wiley-VCH Verlagsgesellschaft. - 1862-6351. ; 5:5, s. 1438-1441
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Tidskriftsartikel (refereegranskat)abstract
- Methodology for studies of effects of heating multilayers of human serum albumin (HSA) and anti-HSA is presented. Multilayers of anti-HSA were prepared on silicon substrates and studied with infrared spectroscopic ellipsometry equipped with a heat stage. The refractive index N = n + ik and the layer thickness are determined and the amide bands are analyzed. It is found that HSA/anti-HSA multilayers are stable for shorter times at temperatures above 100 °C, except for small thickness changes. Also pilot studies of effects of heating monolayers of proteins adsorbed on gold substrates is presented.
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| 5. |
- Bakker, Jimmy W.P., et al.
(författare)
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Immunodetection using computer screen photo-assisted ellipsometry
- 2008
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Ingår i: Physica Status Solidi. C: Current Topics in Solid State Physics. - Weinheim, Germany : Wiley-VCH Verlagsgesellschaft. - 1862-6351. ; 5:5, s. 1431-1433
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Tidskriftsartikel (refereegranskat)abstract
- Detection of antibody-antigen reactions is demonstrated by measuring changes in reflectance of light polarized parallel to the plane of incidence, using a computer screen as light source and a web camera as detector, giving results similar to traditional off-null ellipsometry and in accordance with a simplified theoretical model.
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| 6. |
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| 7. |
- Berlind, Torun, 1965-, et al.
(författare)
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Effects of ion concentration on refractive indices offluids measured by the minimum deviation technique
- 2008
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Ingår i: Physica Status Solidi. C, Current topics in solid state physics. - Weinheim : WILEY-VCH Verlag GmbH & Co. KGaA. - 1610-1634 .- 1610-1642. ; 5:5, s. 1249-1252
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Tidskriftsartikel (refereegranskat)abstract
- The prism minimum deviation technique has been used to measure the fluid dependence of refractive indices. Fluids with varying ion concentration (0 to 1.0 M) and varying protein concentration (0.01-10 mg/ml) have been examined and the measurements show that these parameters influence the refractive index values. Also it is shown by simulations that it is important to take the change of refractive index of the fluid into account when evaluating insitu protein adsorption measurements.
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| 8. |
- Bi, Zhaoxia, et al.
(författare)
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InN quantum dots on GaN nanowires grown by MOVPE
- 2014
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Ingår i: physica status solidi (c). - : Wiley. - 1862-6351 .- 1610-1642 .- 1610-1634. ; 11, s. 421-424
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Tidskriftsartikel (refereegranskat)abstract
- In this work, growth of InN quantum dots (QDs) on GaN nanowires (NWs) by metal-organic vapour phase epitaxy is demonstrated, illustrating the feasibility to combine 0D and 1D structures for nitride semiconductors. Selective area growth was used to generate arrays of c-oriented GaN NWs using Si3N4 as the mask material. In general, InN QDs tend to form at the NW edges between the m-plane side facets, but the QD growth can also be tuned to the side facets by controlling the growth temperature and the growth rate. TEM characterization reveals that I1-type stacking faults are formed in the QDs and originate from the misfit dislocations at the InN/GaN interface. Photoluminescence measurement at 4 K shows that the peak shifts to high energy with reduced dot size. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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| 9. |
- Campoy-Quiles, M., et al.
(författare)
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On the determination of anistropy in polymer thin films : A comparative study of optical techniques
- 2008
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Ingår i: Physica Status Solidi. C: Current Topics in Solid State Physics. - Weinheim, Germany : Wiley-VCH Verlagsgesellschaft. - 1862-6351. ; 5:5, s. 1270-1273
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Tidskriftsartikel (refereegranskat)abstract
- We have used seven different techniques to measure the anisotropic refractive index of poly(vinylcarbazole) films. These techniques are: two types of variable angle spectroscopic ellipsometry (VASE) with multiple sample analysis, Interference enhanced VASE, Transmittance combined with VASE, Polarised Reflectance, beta-scan VASE, and prism coupling. We have found the average ordinary and extraordinary indices at 633 nm to be no = nTE = 1.675 ± 0.008, and ne = nTM = 1.722 ± 0.018, respectively, consistent amongst methods and conclusive on the magnitude of Δn in polymer films.
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| 10. |
- Chulapakorn, Thawatchart, 1988-, et al.
(författare)
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MeV ion irradiation effects on the luminescence properties of Si-implanted SiO2-thin films
- 2016
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Ingår i: Physica Status Solidi (C) Current Topics in Solid State Physics. - : Wiley-VCH Verlagsgesellschaft. - 1862-6351 .- 1610-1634 .- 1610-1642. ; 13:10-12, s. 921-926
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Tidskriftsartikel (refereegranskat)abstract
- The effects of MeV heavy ion irradiation at varying fluence and flux on excess Si, introduced in SiO2 by keV ion implantation, are investigated by photoluminescence (PL). From the PL peak wavelength (λ) and decay lifetime (τ), two PL sources are distinguished: i) quasi-direct recombination of excitons of Si-nanoparticles (SiNPs), appearing after thermal annealing (λ > 720 nm, τ ∼ μs), and ii) fast-decay PL, possibly due to oxide-related defects (λ ∼ 575-690 nm, τ ∼ ns). The fast-decay PL (ii) observed before and after ion irradiation is induced by ion implantation. It is found that this fast-decay luminescence decreases for higher irradiation fluence of MeV heavy ions. After thermal annealing (forming SiNPs), the SiNP PL is reduced for samples irradiated by MeV heavy ions but found to stabilize at higher level for higher irradiation flux; the (ii) band vanishes as a result of annealing. The results are discussed in terms of the influence of electronic and nuclear stopping powers.
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