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- 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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| 2. |
- Hjort, Martin, et al.
(författare)
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Surface Chemistry, Structure, and Electronic Properties from Microns to the Atomic Scale of Axially Doped Semiconductor Nanowires.
- 2012
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851.
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Tidskriftsartikel (refereegranskat)abstract
- Using both synchrotron-based photoemission electron microscopy/spectroscopy and scanning tunneling microscopy/spectroscopy, we obtain a complete picture of the surface composition, morphology, and electronic structure of InP nanowires. Characterization is done at all relevant length scales from micrometer to nanometer. We investigate nanowire surfaces with native oxide and molecular adsorbates resulting from exposure to ambient air. Atomic hydrogen exposure at elevated temperatures which leads to the removal of surface oxides while leaving the crystalline part of the wire intact was also studied. We show how surface chemical composition will seriously influence nanowire electronic properties. However, opposite to, for example, Ge nanowires, water or sulfur molecules adsorbed on the exterior oxidized surfaces are of less relevance. Instead, it is the final few atomic layers of the oxide which plays the most significant role by strongly negatively doping the surface. The InP nanowires in air are rather insensitive to their chemical surroundings in contrast to what is often assumed for nanowires. Our measurements allow us to draw a complete energy diagram depicting both band gap and differences in electron affinity across an axial nanowire p-n junction. Our findings thus give a robust set of quantitative values relating surface chemical composition to specific electronic properties highly relevant for simulating the performance of nanoscale devices.
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| 6. |
- Ouattara, Lassana, et al.
(författare)
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Correlation lengths in stacked InAs quantum dot systems studied by cross-sectional scanning tunnelling microscopy
- 2007
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 18:14
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the influence of the InP spacer layer thickness on stacked InAs/InP quantum dots, using cross-sectional scanning tunnelling microscopy. We show that for a spacer layer thickness of up to 30 nm, the quantum dots are spatially correlated but for a separating distance of 50 nm the vertical ordering of the dots is lost. These values are the same as previously found for quantum dots in the InAs/GaAs system despite the large difference in lattice mismatch between the InAs/GaAs ( 7%) and InAs/InP ( 3%) systems. We show that the apparent similarities can be understood by a combination of intermixing in the dots and differences in dot size. Finally, we demonstrate that the size of the quantum dots is affected by their vertical correlation.
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| 7. |
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| 8. |
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| 9. |
- Ouattara, Lassana, et al.
(författare)
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Stacked InAs quantum dots in InP studied by cross-sectional scanning tunnelling microscopy
- 2004
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 15:12, s. 1701-1707
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Tidskriftsartikel (refereegranskat)abstract
- We report on cross-sectional scanning tunnelling microscopy (XSTM) measurements on vertically stacked InAs quantum dots in InP barriers. We have investigated two-, five- and tenfold stacked quantum dot structures,grown by low-pressure metal-organic vapour phase epitaxy. The XSTM images reveal that the quantum dots are generally vertically well aligned, and have a truncated pyramidal shape in agreement with similar studies of InAs dots in GaAs. STM images displaying atomic resolution indicate that the dots have a pure InAs stoichiometry, with intermixing only occurring in the top and bottom dot rows. Further, we have investigated various anomalies (considered as defects) as observed in the quantum dot stacks. The origins of these anomalies are discussed and compared to theoretical predictions available so far.
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