| 51. |
- Borgström, Magnus, et al.
(författare)
-
Site-control of InAs quantum dots on a patterned InP surface: As/P exchange reactions
- 2002
-
Ingår i: 7th International Conference on Nanometer-Scale Science and Technology and 21st European Conference on Surface Science.
-
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
|
|
| 52. |
- Borgström, Magnus, et al.
(författare)
-
Site-controlled Ge quantum dot growth on Si by the use of electron beam pre-patterning
- 2002
-
Ingår i: 7th International Conference on Nanometer-Scale Science and Technology and 21st European Conference on Surface Science.
-
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)
|
|
| 53. |
- Borgström, Magnus, et al.
(författare)
-
Size- and shape-controlled GaAs nano-whiskers grown by MOVPE: a growth study
- 2004
-
Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 260:1-2, s. 18-22
-
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.
|
|
| 54. |
- Borgström, Magnus, et al.
(författare)
-
Spontaneous InAs quantum dot nucleation at strained InP/GaInAs interfaces
- 2003
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 83:23, s. 4830-4832
-
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.
|
|
| 55. |
- Borgström, Magnus T., et al.
(författare)
-
Towards Nanowire Tandem Junction Solar Cells on Silicon
- 2018
-
Ingår i: IEEE Journal of Photovoltaics. - 2156-3381. ; 8:3, s. 733-740
-
Tidskriftsartikel (refereegranskat)abstract
- The development of photovoltaics as a serious means of producing renewable energy has accelerated greatly in the last ten years, with prices for silicon-based solar cell systems dropping dramatically in the last few years. The next great opportunity for photovoltaics following this competitiveness in prices will be to enhance the cell and panel efficiencies. It is quite generally seen that the most viable platform on which this should be realized will be as augmented silicon solar cells, in which a top cell will be combined with the silicon bottom cell in a tandem configuration, by which the efficiency can be enhanced by a factor from 20% to 50%, depending on details of the approach. In this paper, we report on the status of one such approach, namely, with a top cell comprising III-V nanowires, connected to the bottom silicon cell in a two-terminal or four-terminal configuration. Among the most important opportunities, we show that a substrate-free growth, called Aerotaxy, offers a radical reduction in the total price picture. Besides the description of the key technical approaches, we also discuss the environmental issues.
|
|
| 56. |
- Borschel, Christian, et al.
(författare)
-
A New Route toward Semiconductor Nanospintronics : Highly Mn-Doped GaAs Nanowires Realized by Ion-Implantation under Dynamic Annealing Conditions
- 2011
-
Ingår i: Nano letters (Print). - Washington : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 11:9, s. 3935-3940
-
Tidskriftsartikel (refereegranskat)abstract
- We report on highly Mn-doped GaAs nanowires (NWs) of high crystalline quality fabricated by ion beam implantation, a technique that allows doping concentrations beyond the equilibrium solubility limit. We studied two approaches for the preparation of Mn-doped GaAs NWs: First, ion implantation at room temperature with subsequent annealing resulted in polycrystalline NWs and phase segregation of MnAs and GaAs. The second approach was ion implantation at elevated temperatures. In this case, the single-crystallinity of the GaAs NWs was maintained, and crystalline, highly Mn-doped GaAs NWs were obtained. The electrical resistance of such NWs dropped with increasing temperature (activation energy about 70 meV). Corresponding magnetoresistance measurements showed a decrease at low temperatures, indicating paramagnetism. Our findings suggest possibilities for future applications where dense arrays of GaMnAs nanowires may be used as a new kind of magnetic material system.
|
|
| 57. |
|
|
| 58. |
- Boyd, Erin E., et al.
(författare)
-
Scanning gate imaging of quantum dots in 1D ultra-thin InAs/InP nanowires
- 2011
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 22:18
-
Tidskriftsartikel (refereegranskat)abstract
- We use a scanning gate microscope (SGM) to characterize one-dimensional ultra-thin (diameter approximate to 30 nm) InAs/InP heterostructure nanowires containing a nominally 300 nm long InAs quantum dot defined by two InP tunnel barriers. Measurements of Coulomb blockade conductance versus backgate voltage with no tip present are difficult to decipher. Using the SGM tip as a charged movable gate, we are able to identify three quantum dots along the nanowire: the grown-in quantum dot and an additional quantum dot near each metal lead. The SGM conductance images are used to disentangle information about individual quantum dots and then to characterize each quantum dot using spatially resolved energy-level spectroscopy. S Online supplementary data available from stacks.iop.org/Nano/22/185201/mmedia
|
|
| 59. |
|
|
| 60. |
- Bryllert, Tomas, et al.
(författare)
-
Designed emitter states in resonant tunneling through quantum dots
- 2002
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 80:15, s. 2681-2683
-
Tidskriftsartikel (refereegranskat)abstract
- Resonant tunneling through a single layer of self-assembled quantum dots (QDs) is compared to tunneling through two layers of vertically aligned (stacked) dots. The difference can be viewed as going from a two-dimensional emitter to a zero-dimensional emitter. The temperature dependence of current peaks originating in tunneling through individual QDs and individual stacks is used to clarify this point. In addition, we show that the statistical size distribution of self-assembled quantum dots causing the inhomogeneous broadening in luminescence experiments can be analyzed in a resonant tunneling experiment. (C) 2002 American Institute of Physics.
|
|
