| 1. |
- Donchev, V., et al.
(författare)
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Photoluminescene line-shape analysis in quantum wells embedded in superlattices
- 2001
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Ingår i: Materials science & engineering. C, biomimetic materials, sensors and systems. - 0928-4931 .- 1873-0191. ; 15:1-2, s. 75-77
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Tidskriftsartikel (refereegranskat)abstract
- The temperature evolution of the main photoluminescence (PL) mechanisms, in GaAs quantum wells embedded in short-period AlAs/GaAs superlattices, is investigated. PL spectra are measured from 2 to 300 K. A detailed line-shape analysis of the PL peaks is performed by means of a statistical model, including both free exciton and free carrier recombination. The fits based on this model reproduce satisfactorily the experimental PL line shapes and allow to assess quantitatively the relative contributions of free excitons and free carriers to the radiative recombination at different temperatures. The results indicate the predominant role of free excitons in the radiative recombination up to room temperature, and are consistent with the mass action law. © 2001 Elsevier Science B.V. All rights reserved.
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| 3. |
- Tatte, T, et al.
(författare)
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Transparent and conductive Sb-doped tin oxide SPM tips prepared by sol-gel method
- 2002
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Ingår i: Materials Science and Engineering C: Materials for Biological Applications. - 0928-4931. ; 19:1-2, s. 101-104
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Tidskriftsartikel (refereegranskat)abstract
- The rapid progress in scanning probe microscopy (SPM) techniques in the last decade has induced an increasing need for manufacturing advanced SPM tips. One important case is conductive and transparent tips. For such tips, only a few techniques have been proposed. which are either expensive or have poor reproducibility. We here propose a simple and cheap sol-gel technique to prepare fibers with a suitably sharp apex so that they can be used as SPM tips. The fibers were spinned off from a high-viscosity solution of tin alkoxide and SbCl3 hydrolysed in hurnid air and baked at 520 degreesC for several hours. The radii of the resulting tips were estimated by transmission electron microscopy to be less than 50 am. The resistivity of the transparent fibers was measured using different Sb-doping (0.5-1 wt.%) of the tin oxide, The temperature dependence of the conductivity and light absorption were investigated down to liquid He temperatures.
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| 4. |
- Xu, Hongqi, et al.
(författare)
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A novel device principle for nanoelectronics
- 2002
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Ingår i: Materials Science and Engineering C: Materials for Biological Applications. - 0928-4931. ; 19:1-2, s. 417-420
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Tidskriftsartikel (refereegranskat)abstract
- We report on the results of our recent theoretical and experimental investigations of a novel, room temperature electrical property of three-terminal ballistic junctions (TBJs). For a symmetric TBJ device, it is found that when finite voltages V-1 and V-r are applied in push-pull fashion, with V-1 = V and V-r = - V. to the left and right branches, the voltage output V-c from the central branch will always be negative. This property is in strong contrast to a symmetric three-terminal device made from conventional diffusive conductors, for which Ohm's law predicts a constant zero output of V-c for all V-1 - V-c.This novel characteristic appears even when the device symmetry is broken, provided that V is greater than the threshold. It is also shown that the TBJ devices show a good parabolic behavior for V-c vs. V in a large range of voltages V.
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| 5. |
- Bahroudi, A, et al.
(författare)
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Effect of ductile and frictional decollements on style of extension
- 2003
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Ingår i: Journal of Structural Geology. - 0191-8141 .- 1873-1201. ; 25:9, s. 1401-1423
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Tidskriftsartikel (refereegranskat)abstract
- Scaled analogue models were used to study the effect of frictional and ductile detachments on thin-skinned extension. Models consisted of two halves; one half is the ductile and the other has a frictional detachment. Extension occurred above two different basal configurations: a stretchable rubber sheet and a folded, banded sheet intended to produce homogeneous and heterogeneous extension, respectively. Model parameters varied systematically and included the brittle/ductile thickness ratio, rheologies, and bulk strain. Structures in the two halves are compared in profiles and plan views. A series of graben developed above both halves of models extended above a banded sheet, although there were differences in style, propagation rate and width of the deformation zone between the two halves. Different rates of propagation of structures in the two halves led to the formation of an accommodation or transfer zone parallel to the extension direction. Most relay ramps and inflection of normal faults in this zone indicate differential extension between the two halves.In contrast, in models extended above a stretchable rubber sheet, extensional structures such as horst and graben developed only above the ductile detachment. Model results indicate that heterogeneous mechanical stratigraphy and displacement rate have no effect on extensional structure above a rubber sheet. However, above 20% bulk extension, deformation becomes heterogeneous along multiple sets of conjugate faults oblique to the extension direction.
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| 9. |
- Harris, Lyal, et al.
(författare)
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Centrifuge modelling of folding in high grade rocks during rifting
- 2003
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Ingår i: Journal of Structural Geology. - : Elsevier. - 0191-8141 .- 1873-1201. ; 25:2, s. 291-305
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Tidskriftsartikel (refereegranskat)abstract
- Centrifuge modelling is used to simulate the progressive development of structures in a simplified crustal profile during rifting. This paper focuses on folding of ductile layers representing the middle to lower crust. Displacement along a pre-existing cut in the layer representing mantle lithosphere creates a broad shear zone in overlying ductile layers and an asymmetric rift in upper layers. The footwall of the ‘mantle lithosphere’ layer and overlying shear zone are rotated to sub-horizontal during rise of the basal ductile layer (representing asthenosphere) as an isostatic response to thinning in the extended model. Synthetic and antithetic faults develop in models with thicker ductile ‘crustal’ layers. Although upper, semi-brittle layers, representing upper crust constitute a simple fault-bounded or sag ‘basin’, the underlying ductile layers are complexly folded. Open, upright folds developed over the crest of the footwall ‘mantle lithosphere’ layer are tightened and increased in amplitude as they progressively rotate to a recumbent attitude. Refolding occurs during rise of the basal ductile material representing asthenosphere and from boudinage of overlying competent layers. This study suggests that regional-scale folds in some high-grade terrains previously interpreted as evolving in a convergent margin tectonic setting may instead be produced as a result of flow of the ductile crust during rifting.
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