| 1. |
- Persson, Clas Marcus, et al.
(författare)
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Electronic band-edge structure, effective masses, and optical absorption of Si1-xGex using an extended FPLAPW/VCA/LDA+U computational method
- 2006
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Ingår i: Brazilian journal of physics. - : Sociedade Brasileira de Fisica. - 0103-9733 .- 1678-4448. ; 36:2 A, s. 447-450
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Tidskriftsartikel (refereegranskat)abstract
- Electronic band-edge structure and optical properties of Si 1-xGex are investigated theoretically emloying a full-potential linearized augmented plane wave (FPLAPW) method. The exchange-correlation potential in the local density approximation (LDA) is corrected by an on-site Coulomb potential (i.e., within the LDA.+USIC approach) acting asymmetrically on the atomic-like orbitals in the muffin-tin spheres. The electronic structure of the Si1-xGex is calculated self-consistently, assuming a Td symmetrized Hamiltonian and a linear behavior of the valence-band eigenfunctions for Si, SiGe, and Ge with respect to Ge composition x, assuming randomly alloyed crystal structure, i.e., a "virtual-crystal like" approximation (VGA). We show that this approach yields accurate band-gap energies, effective masses, dielectric function, and optical properties of Si1-xGex. We perform absorption measurements showing the band-gap energy for x < 0.25.
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| 2. |
- Da Silva, A. F., et al.
(författare)
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Linear optical response of Si1-xGex compounds
- 2005
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Ingår i: Quantum Sensing and Nanophotonic Devices II. - : SPIE - International Society for Optical Engineering. - 081945706X ; 5732:1, s. 556-564
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Konferensbidrag (refereegranskat)abstract
- Si1-xGex is a good candidate as a substitute material for Si in a low-power and high-speed semiconductor device technologies. Optical devices, such as heterojunction bipolar transistors, are already in industrial production. The samples are grown on Si(001) with both n-and p-type impurities and with different Ge concentrations. The linear optical response of Si 1-x Gex is investigated theoretically using a full-potential linearized augmented plane wave method with respect to composition x. The calculated real and imaginary parts of the dielectric function ε e(ω) = ε1(ω) + iε 2(ω) were found to be in good agreement with recent spectroscopic ellipsometry measurements performed by Bahng et al., J. Phys.: Condens. Matter 13, 777 (2001). We also perform absorption measurements for different type of samples showing the variation of energy gaps as a function of Ge concentrations.
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| 3. |
- Ericson, Ann-Charlott, et al.
(författare)
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The Effects of Capsaicin on Gastrin Secretion in Isolated Human Antral Glands : Before and After Ingestion of Red Chilli
- 2009
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Ingår i: Digestive Diseases and Sciences. - : Springer Science and Business Media LLC. - 0163-2116 .- 1573-2568. ; 54:3, s. 491-498
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Tidskriftsartikel (refereegranskat)abstract
- Background: Capsaicin is known to have regulatory effects on gastrointestinal functions via the vanilloid receptor (VR1). We reported previously that endocrine-like cells in the human antrum express VR1. Aim: To identify VR1-expressing endocrine-like cells in human antral glands and to examine whether stimulation with capsaicin causes release of gastrin, somatostatin, and serotonin. Further, to investigate the effects of a chilli-rich diet. Methods: Gastroscopic biopsies were received from 11 volunteers. Seven of the 11 subjects agreed to donor gastric biopsies a second time after a 3-week chilli-rich diet containing 1.4-4.2 mg capsaicin/day. VR1-immunoreactive cells were identified by double-staining immunohistochemistry against gastrin, somatostatin, and serotonin. For the stimulation studies, we used an in vitro method where antral glands in suspension were stimulated with 0.01 mM capsaicin and physiological buffer was added to the control vials. The concentrations of secreted hormones were detected and calculated with radioimmunoassay (RIA). Results: The light microscopic examination revealed that VR1 was localized in gastrin cells. The secretory studies showed an increase in release of gastrin and somatostatin compared to the control vials (P = 0.003; P = 0.013). Capsaicin-stimulation caused a consistent raise of the gastrin concentrations in the gland preparations from all subjects. A chilli-rich diet had an inhibitory effect on gastrin release upon stimulation compared to the results that were obtained before the start of the diet. Conclusion: This study shows that capsaicin stimulates gastrin secretion from isolated human antral glands, and that a chilli-rich diet decreases this secretion.
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| 4. |
- Willander, Magnus, 1948, et al.
(författare)
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Fundamentals and properties of zinc oxide nanostructures: optical and sensing applications
- 2008
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Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 43:4, s. 352-61
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we will give an overview of the status of catalytic growth and of low-temperature chemical growth of ZnO nanostructures performed in our laboratory. Particularly results employing different substrates will be discussed. The second part deals with structural and optical properties of ZnO nanorods. The results from high resolution transmission electron microscope (HRTEM), scanning electron microscope (SEM), photoluminescence (PL), Cathodoluminescence (CL), and Electroluminescence (EL), on single nanowires will be shown. Our results on surface morphology, bulk and the position of the catalyst as well as the optical properties including UV emission, lasing and white emission will all be presented and discussed. In the third part experimental results from electroluminescence of ZnO nanorods on different substrates in the UV in addition to excellent white light emission obtained from samples grown at low temperature are to be given and discussed. Finally the sensing of molecules in water by ZnO nanorods will be discussed from a theoretical point of view. Also fundamental properties of polaritons and excitons in ZnO nanostructures are to be highlighted.
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| 5. |
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| 6. |
- Willander, Magnus, 1948, et al.
(författare)
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Solid and soft nanostructured materials: fundamentals and applications
- 2005
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Ingår i: Microelectronics Journal. - : Elsevier BV. - 0026-2692. ; 36:11, s. 940-949
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Tidskriftsartikel (refereegranskat)abstract
- The scientific work worldwide on nanostructured materials is extensive as well as the work on the applications of nanostructured materials. We will review quasi two-, one- and zero-dimensional solid and soft materials and their applications. We will restrict ourselves to a few examples from partly fundamental aspects and partly from application aspects. We will start with trapping of excitons in semiconductor nanostructures. The subjects are: physical realizations, phase diagrams, traps, local density approximations, and mesoscopic condensates. From these fundamental questions in solid nanomaterials we will move to trapping of molecules in water using nanostructured electrodes. We will also discuss how to manipulate water (create vortices) by nanostructure materials. The second part deals with nanorods (nano-wires). Particularly we will exemplify with ZnO nanorods. The reason for this is that ZnO has: a very strong excitons binding energy (60 meV) and strong photon–excitons coupling energy, a strong tendency to create nanostructures, and properties which make the material of interest for both optoelectronics and for medical applications. We start with the growth of crystalline ZnO nanorods on different substrates, both crystalline (silicon, silicon carbide, sapphire, etc) and amorphous substrates (silicon dioxide, plastic materials, etc) for temperatures from 50 °C up to 900 °C. The optical properties and crystalline properties of the nanorods will be analyzed. Applications from optoelectronics (lasers, LEDs, lamps, and detectors) are analyzed and also medical applications like photodynamic cancer therapy are taken up. The third part deals with nano-particles in ZnO for sun screening. Skin cancer due to the exposure from the sun can be prevented by ZnO particles in a paste put on the exposed skin.
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