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- Ferdos, Fariba, 1966, et al.
(författare)
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Influence of a thin GaAs cap layer on structural and optical properties of InAs quantum dots
- 2002
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 81:7, s. 1195-7
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Tidskriftsartikel (refereegranskat)abstract
- In this letter we investigate the changes in the surface morphology and emission wavelength of InAs quantum dots (QDs) during initial GaAs encapsulation by atomic force microscopy and photoluminescence. The density (2.9×1010 cm-2) and height (7.9±0.4 nm) of the uncapped QDs decrease and saturate at 0.6×1010 cm-2 and 4 nm, respectively, after the deposition of 4 monolayers (MLs) of GaAs. A model for the evolution of surface morphology is proposed. Photoluminescence spectra of the surface dots show a wavelength shift from 1.58 to 1.22 ?m when the GaAs capping layer thickness increases from 0 to 8 MLs.
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- Ferdos, Fariba, 1966, et al.
(författare)
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Influence of initial GaAs and AlAs cap layers on InAs quantum dots grown by molecular beam epitaxy
- 2003
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 251:1-4, s. 145-9
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Tidskriftsartikel (refereegranskat)abstract
- Capping of InAs quantum dots (QDs) with AlAs or GaAs causes a significant change in the structural properties of the QDs. However, there is a basic difference between these two capping materials. The GaAs capping causes a dramatic reduction of the dot density and height. AlAs capping, on the other hand, results in a partly suppressed height reduction and a higher dot density.
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- Ferdos, Fariba, 1966, et al.
(författare)
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Influence of thin GaAs and AlAs cap layers on the structural properties of InAs quantum dots grown by molecular beam epitaxy
- 2002
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Ingår i: International Conference on Molecular Beam Epitaxy, 2002. ; , s. 285-6
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Konferensbidrag (refereegranskat)abstract
- Self-organised InAs quantum dots (QDs) are used as optical gain material in long wavelength lasers on GaAs. The measured QD height and density are often used as figures of merits, and great efforts have been made to maximise these two parameters to extend the wavelength coverage. In this work, we investigate the influence of initial GaAs and AlAs cap layers on the structural properties of InAs QDs. The study clearly shows that capping of InAs QDs causes a strong modification of not only the QD shape and height but also the QD density
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- Ferdos, Fariba, 1966, et al.
(författare)
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Optimisation of MBE growth conditions for InAs quantum dots on (001) GaAs for 1.3 μm luminescence
- 2001
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 227-228, s. 1140-5
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of the optimised growth conditions for InAs quantum dots (QDs) grown on GaAs substrates by solid source molecular beam epitaxy (SSMBE). Growth conditions for best luminescence intensity and linewidth were found within narrow windows of substrate temperature (500-520°C) and nominal InAs layer thickness (3.3-3.7 monolayers). The emission wavelength of such InAs QDs capped by GaAs was around 1.24 ?m. However, this is redshifted to 1.3 ?m or more by capping the InAs QDs with a thin layer of InxGa1-xAs. The results show that both In content and thickness of the capping layer can be used to tune the emission wavelength. Atomic force microscopy images show that the surface recovers to two-dimensional when depositing In0.2Ga0.8As while remaining three-dimensional when depositing In0.4Ga0.6As.
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- Liu, Qing, et al.
(författare)
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Roquinimex inhibits dextran sodium sulfate-induced murine colitis
- 2003
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Ingår i: Inflammation Research. - : Springer Science and Business Media LLC. - 1420-908X .- 1023-3830. ; 52:2, s. 64-68
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Roquinimex is a modulator of the immune system and has been shown to attenuate induction of several inflammatory and autoimmune diseases. The objective of the present study was to determine the efficacy of roquinimex in a model of murine colitis. Materials and methods: For this purpose, Balb/c mice were exposed to 5% dextran sodium sulfate (DSS) in the drinking water for five to six days. Roquinimex (300 mg kg(-1) day(-1)) was administered by subcutaneous (s.c.) injection 3 days prior to and throughout the treatment period with DSS. In separate experiments, 300 mg kg(-1) day(-1) of roquinimex was given therapeutically after initiation of DSS challenge. Results: DSS provoked clinical signs of colitis, reduced crypt height (CH) and increased mucosal damage score (MDS) as analyzed by histology. In addition, challenge with DSS increased the colonic content of myeloperoxidase (MPO). Prophylactic administration of DSS-treated mice with roquinimex significantly reduced clinical signs of colitis, MDS and the CH-reduction. Moreover, in roquinimex treated animals, the MPO activity was significantly reduced by more than 50% compared to DSS control mice. Notably, therapeutic administration of roquinimex in DSS-treated mice also significantly inhibited the MDS, CH-reduction and MPO activity. Conclusions: These findings suggest that roquinimex strongly inhibits murine colitis and may provide a novel pharmacological approach to treat inflammatory bowel disease.
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- Wan, M X, et al.
(författare)
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Protective effect of low molecular weight heparin on experimental colitis: role of neutrophil recruitment and TNF-alpha production.
- 2002
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Ingår i: Inflammation Research. - 1420-908X. ; 51:4, s. 182-187
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: The purpose of this study was to examine the impact and mechanism of action of low molecular weight heparin (LMWH) in a model of murine colitis. MATERIALS AND METHODS: Balb/c mice were exposed to 5% dextran sodium sulfate (DSS) in the drinking water for five days. LMWH (500 units/kg/day) was administered by subcutaneous injection prior to and throughout the treatment period with DSS. Clinical disease activity index (DAI), including body weight loss, stool consistency and blood in feces were examined daily. Moreover, crypt height (CH), mucosal damage score (MDS), myeloperoxidase (MPO) activity and tumor necrosis factor-alpha (TNF-alpha) content in the colon were determined. RESULTS: DSS increased DAI, MDS, MPO activity and TNF-alpha production and decreased CH. Administration of LMWH markedly reduced DAI, MDS and reversed the CH-reduction. Moreover, in LMWH-treated animals, the MPO activity was reduced by more than 67% whereas mucosal levels of TNF-alpha was similar compared to DSS control mice. CONCLUSIONS: These findings suggest that LMWH inhibits murine colitis by interference with neutrophil recruitment and that LMWH may provide a novel pharmacological approach to treatment of inflammatory bowel disease.
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