| 1. |
- Bolinsson, Jessica, et al.
(författare)
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Wurtzite-zincblende superlattices in InAs nanowires using a supply interruption method.
- 2011
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 22:26
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Tidskriftsartikel (refereegranskat)abstract
- Crystal phase control in single III-V semiconductor nanowires has emerged recently as an important challenge and possible complement to conventional bandgap engineering in single material systems. Here we investigate a supply interruption method for precise crystal phase control in single nanowires. The nanowires are grown by metalorganic vapor phase epitaxy using gold particles as seeds and are analyzed by transmission electron microscopy. It is observed that wurtzite segments with controlled length and position can be inserted on demand into a pure InAs zincblende nanowire. The interface between wurtzite and zincblende segments can be made atomically sharp and the segments can be made only a few bilayers in thickness. The growth mechanisms, applicability and limitations of the technique are presented and discussed.
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| 2. |
- Caroff, Philippe, et al.
(författare)
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InAs film grown on Si(111) by Metalorganic Vapor Phase Epitaxy
- 2008
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 100, s. 042017-042017
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Konferensbidrag (refereegranskat)abstract
- We report the successful growth of high quality InAs films directly on Si( 111) by Metal Organic Vapor Phase Epitaxy. A nearly mirror-like and uniform InAs film is obtained at 580 C for a thickness of 2 mu m. We measured a high value of the electron mobility of 5100 cm(2)/Vs at room temperature. The growth is performed using a standard two-step procedure. The influence of the nucleation layer, group V flow rate, and layer thickness on the electrical and morphological properties of the InAs film have been investigated. We present results of our studies by Atomic Force Microscopy, Scanning Electron Microscopy, electrical Hall/van der Pauw and structural X-Ray Diffraction characterization.
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| 3. |
- Chamard, Virginie, et al.
(författare)
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Evidence of stacking-fault distribution along an InAs nanowire using micro-focused coherent X-ray diffraction
- 2008
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Ingår i: Journal of Applied Crystallography. - 1600-5767. ; 41:Part 2, s. 272-280
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Tidskriftsartikel (refereegranskat)abstract
- InAs nanowire samples grown by metal-organic chemical vapor deposition present a significant amount of wurtzite structure, while the zincblende lattice is known to be the stable crystal structure for the bulk material. The question of the wurtzite distribution in the sample is addressed using phase-sensitive coherent X-ray diffraction with a micro-focused beam at a synchrotron source. The simultaneous investigation of the wurtzite 10 (1) over bar0, 10 (2) over bar0, 10 (3) over bar0 reflections performed on a bunch of single wires shows unambiguously that the wurtzite contribution is a result of stacking faults distributed along the wire. Additional simulations lead to adjustments of the wire structural parameters, such as the wurtzite content, the strain distribution, the wire diameters and their respective orientations.
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| 4. |
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| 5. |
- Fian, Alexander, et al.
(författare)
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New Flexible Toolbox for Nanomechanical Measurements with Extreme Precision and at Very High Frequencies.
- 2010
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 10:Online August 26, 2010, s. 3893-3898
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Tidskriftsartikel (refereegranskat)abstract
- We show that the principally two-dimensional (2D) scanning tunneling microscope (STM) can be used for imaging of 1D micrometer high free-standing nanowires. We can then determine nanowire megahertz resonance frequencies, image their top-view 2D resonance shapes, and investigate axial stress on the nanoscale. Importantly, we demonstrate the extreme sensitivity of electron tunneling even at very high frequencies by measuring resonances at hundreds of megahertz with a precision far below the angstrom scale.
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| 6. |
- Hjort, Martin, et al.
(författare)
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Surface morphology of Au-free grown nanowires after native oxide removal.
- 2015
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 7:22, s. 9998-10004
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Tidskriftsartikel (refereegranskat)abstract
- Using scanning tunneling microscopy, we evaluate the surface structure and morphology down to the atomic scale for micrometers along Au-free grown InAs nanowires (NWs) free from native oxide. We find that removal of the native oxide (which covers the NWs upon exposure to the ambient air) using atomic hydrogen does not alter the underlying step structure. Imaging with sub-nanometer resolution along the NWs, we find an extremely low tapering (diameter change along the NW) of 1.7 ± 0.5 Åμm(-1). A surface morphology with monolayer high islands, whose shape was influenced by stacking faults, was found to cover the NWs and was attributed to the decomposed native oxide. The appearance of point defects in the form of As-vacancies at the surface is analyzed and we set limits to the amount of carbon impurities in the NWs.
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| 7. |
- Keplinger, Mario, et al.
(författare)
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Core-shell nanowires: From the ensemble to single-wire characterization
- 2010
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 268:3-4, s. 316-319
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Konferensbidrag (refereegranskat)abstract
- Recent investigations of core-shell nanowires using synchrotron radiation techniques deduced the average structural parameters of heterostructure core-shell nanowires. Here, we report on first results and discuss the problems arising when measuring such complex nanostructures by using nanofocusing X-ray techniques. InAs/IAsP core-shell nanowires exhibit a certain bending, the origin of which is described using finite element simulations assuming a displacement of the core, and a gradient in the chemical composition of the wire's shell. (C) 2009 Elsevier B.V. All rights reserved.
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| 8. |
- Keplinger, Mario, et al.
(författare)
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Structural Investigations of Core-shell Nanowires Using Grazing Incidence X-ray Diffraction.
- 2009
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 9:5, s. 1877-1882
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Tidskriftsartikel (refereegranskat)abstract
- The fabrication of core-shell structures is crucial for many nanowire device concepts. For the proper tailoring of their electronic properties, control of structural parameters such as shape, size, diameter of core and shell, their chemical composition, and information on their strain fields is mandatory. Using synchrotron X-ray diffraction studies and finite element simulations, we determined the chemical composition, dimensions, and strain distribution for series of InAs/InAsP core-shell wires grown on Si(111) with systematically varied growth parameters. In particular we detect initiation of plastic relaxation of these structures with increasing shell thickness and/or increasing phosphorus content. We establish a phase diagram, defining the region of parameters leading to pseudomorphic nanowire growth. This is important to avoid extended defects which are detrimental for their electronic properties.
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| 9. |
- Keplinger, Mario, et al.
(författare)
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X-ray diffraction strain analysis of a single axial InAs1-xPx nanowire segment.
- 2015
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Ingår i: Journal of Synchrotron Radiation. - 1600-5775. ; 22:Pt 1, s. 59-66
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Tidskriftsartikel (refereegranskat)abstract
- The spatial strain distribution in and around a single axial InAs1-xPx hetero-segment in an InAs nanowire was analyzed using nano-focused X-ray diffraction. In connection with finite-element-method simulations a detailed quantitative picture of the nanowire's inhomogeneous strain state was achieved. This allows for a detailed understanding of how the variation of the nanowire's and hetero-segment's dimensions affect the strain in its core region and in the region close to the nanowire's side facets. Moreover, ensemble-averaging high-resolution diffraction experiments were used to determine statistical information on the distribution of wurtzite and zinc-blende crystal polytypes in the nanowires.
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| 10. |
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