| 1. |
- Aberg, I, et al.
(författare)
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Nanoscale tungsten aerosol particles embedded in GaAs
- 2002
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 80:16, s. 2976-2978
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Tidskriftsartikel (refereegranskat)abstract
- GaAs containing buried nanoscale tungsten particles has been characterized electrically. The particles were produced using a special aerosol process and were embedded in GaAs by epitaxial overgrowth. Two different particle sizes were investigated separately. When the particle concentration was increased, a conductance drop of about 500 times was observed. A simulation model, based on a random distribution of the particles, was developed and used to support our findings. The major advantage of our method is the simplicity and low processing cost.
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| 2. |
- Achermann, M, et al.
(författare)
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Carrier and field dynamics around nanoscale Schottky contacts investigated by ultrafast near-field optics
- 2002
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 65:4
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Tidskriftsartikel (refereegranskat)abstract
- We present femtosecond-resolved optical near-field pump-probe measurements of spatiotemporal carrier dynamics around a single nanoscale tungsten (W) disk embedded in GaAs. In these samples, Schottky contacts are formed at the W/GaAs interface. The experimental results are modeled by a selfconsistent treatment of the drift-diffusion equation for the carriers and Poisson's equation for the built-in electric field. At lower optically excited carrier densities, we observe that the built-in field suppresses electron transport towards and trapping into the metal particles. In this regime, an accumulation of carriers is seen at the edge of the depletion region of the Schottky contacts. The calculation reveals that the formation of a self-induced dynamic potential well is the origin of this result. In the high-density regime, efficient carrier transport towards and trapping into the W nanoparticle take place, resulting from the screening of the built-in field. These results allow us to describe measurements of the carrier dynamics in annealed low-temperature grown GaAs and demonstrate that the coupling of the carrier and field dynamics can substantially affect carrier trapping in metal-semiconductor composite materials.
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| 3. |
- Borgström, Magnus, et al.
(författare)
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Arrays of Ge islands on Si(001) grown by means of electron-beam pre-patterning
- 2003
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484. ; 14:2, s. 264-267
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Tidskriftsartikel (refereegranskat)abstract
- We show that well-defined arrays of self-assembled Ge dots on Si(001) can be grown after pre-patterning the Si surface by means of an electron beam. The electron beam produces C-containing growth masks. The overgrowth of these masks with Si results in pits at the Si surface, in and around which Ge dots nucleate selectively. A manifold of different arrays can be obtained. Almost perfect arrays of quadruples of dots nucleate in the intersections of the four {11n} facets. This way of producing quantum dot arrays is very promising for producing dot structures suitable for use in the study of, for instance, dot-dot tunnelling and related effects.
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| 4. |
- Borgström, Magnus, et al.
(författare)
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InAs quantum dots grown on InAlGaAs lattice matched to InP
- 2003
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 252:4, s. 481-485
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present InAs quantum dots prepared on an InxAlyGa1-x-yAs surface by metal organic vapor phase epitaxy. Atomic force microscopy measurements indicate that dots grown on material with higher Al content are smaller, and that the local dot densities on step-bunched facets formed on the vicinal (0 0 1) surfaces increase. We find that these dots show luminescence at very long wavelengths, lambda(room temperature) approximate to 2.1 mum, and that the emission wavelengths are blue-shifted when the Al content is increased in the layer onto which dot material is deposited. (C) 2003 Elsevier Science B.V. All rights reserved.
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| 5. |
- Borgström, Magnus, et al.
(författare)
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Quadruples of Ge dots grown on patterned Si surfaces
- 2003
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 259:3, s. 262-266
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present the results of Ge deposition on a pre-pattemed Si surface. By partially overgrowing nanometer-sized electron beam-induced carbon deposits, faceted pits form at the Si surface and well-defined arrays of self-assembled Ge dots can be grown site selectively in and around those. Typically, four closely spaced Ge islands are formed by preferential nucleation around the pits. By varying the pattern of C-deposits a manifold of different arrays can be obtained. (C) 2003 Elsevier B.V. All rights reserved.
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| 6. |
- Borgström, Magnus, et al.
(författare)
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Site control of InAs quantum dots on a patterned InP surface: As/P exchange reactions
- 2003
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Ingår i: Journal of Crystal Growth. - 0022-0248. ; 248, s. 310-316
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Tidskriftsartikel (refereegranskat)abstract
- In this paper. we present the effect of annealing temperature and annealing time on InAs site-controlled quantum dot growth. Individual InAs quantum dots formed by self-assembling have been positioned into holes, created by partial overgrowth of electron beam induced nano-carbon deposits by metal organic vapor phase epitaxy. As/P exchange reactions produce material sufficient for selective dot nucleation in the holes. Results. showing that As/P exchange reactions occur even when capping the dots with InP are presented. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 7. |
- Borgström, Magnus, et al.
(författare)
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Site-control of InAs quantum dots on a patterned InP surface: As/P exchange reactions
- 2002
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Ingår i: 7th International Conference on Nanometer-Scale Science and Technology and 21st European Conference on Surface Science.
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Konferensbidrag (refereegranskat)abstract
- We present the effect of annealing temperature and annealing time on InAs/InP site-controlled quantum dot growth. Electron beam pre-patterning forms carbon nano-deposits at the InP surface, which then can be used as growth masks to form nano-holes at the surface. By only annealing of the patterned InP surface under an arsine ambient, As/P exchange reactions produce material sufficient for selective dot nucleation in the holes at the surface
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| 8. |
- Borgström, Magnus, et al.
(författare)
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Site-controlled Ge quantum dot growth on Si by the use of electron beam pre-patterning
- 2002
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Ingår i: 7th International Conference on Nanometer-Scale Science and Technology and 21st European Conference on Surface Science.
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Konferensbidrag (refereegranskat)abstract
- By growth of Si on substrates that have been pre-patterned by electron-beam induced carbon nano-growth masks, nano-holes form at the Si surface. We have grown self-assembled Ge quantum dots in these holes by ultra high vacuum chemical vapour phase deposition (UHV-CVD). We usually find four dots in each hole. By varying the amount of deposited Ge, we can obtain either four dome-shaped or four pyramid-shaped dots in the majority of holes. These dot arrangements could be used for the realisation of the simplest functional cell for quantum-dot cellular automata (QCA)
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| 9. |
- Borgström, Magnus, et al.
(författare)
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Size- and shape-controlled GaAs nano-whiskers grown by MOVPE: a growth study
- 2004
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 260:1-2, s. 18-22
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the Au-catalyzed GaAs <111 > B whisker growth under low-pressure metal-organic vapour phase epitaxy conditions. By varying the growth temperature we found a maximum in the whisker growth rate at about 450-475degreesC. With increasing temperature the growth rate decreases due to competing growth at the (111) substrate surface and at the {I 101 whisker side facets, which leads to significant tapering of the whiskers. For low temperatures, the growth rate R in the In R = f (1/T)-plot results in an Arrhenius activation energy of about 67-75 kJ/mol, a value which is in agreement with activation energies reported for low-temperature planar growth of GaAs from TMG and AsH3. The Au acts as a local catalyst and as a collector of reactants, enabling a liquid-phase-epitaxy-like growth with high growth rates at the GaAs (111)B/(Au,Ga) interface.
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| 10. |
- Borgström, Magnus, et al.
(författare)
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Spontaneous InAs quantum dot nucleation at strained InP/GaInAs interfaces
- 2003
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 83:23, s. 4830-4832
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Tidskriftsartikel (refereegranskat)abstract
- We present a cross-sectional scanning-tunneling microscopy investigation of twofold stacked InAs quantum dots in InP, between layers of GaInAs. The dots are vertically aligned, and images with atomic resolution show that the dots consist of pure InAs. Despite the intended twofold stacking of dots, three dots were often found in the stacks. The third dot formed immediately on top of the final InP layer, at the InP/GaInAs interface. Atomically resolved images of these spontaneously formed dots indicate that they also consist of pure InAs. The effect is discussed in terms of phase segregation of GaInAs and arsenic-phosphorus exchange reactions. (C) 2003 American Institute of Physics.
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