| 1. |
- Björk, Mikael, et al.
(författare)
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Tunable effective g factor in InAs nanowire quantum dots
- 2005
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 72:20
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Tidskriftsartikel (refereegranskat)abstract
- We report tunneling spectroscopy measurements of the Zeeman spin splitting in InAs few-electron quantum dots. The dots are formed between two InP barriers in InAs nanowires with a wurtzite crystal structure grown using chemical beam epitaxy. The values of the electron g factors of the first few electrons entering the dot are found to strongly depend on dot size. They range from close to the InAs bulk value in large dots vertical bar g(*)vertical bar=13 down to vertical bar g(*)vertical bar=2.3 for the smallest dots.
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| 2. |
- Bleszynski-Jayich, Ania C., et al.
(författare)
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Imaging a one-electron InAs quantum dot in an InAs/InP nanowire
- 2008
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 77:24
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Tidskriftsartikel (refereegranskat)abstract
- Nanowire heterostructures define high-quality few-electron quantum dots for nanoelectronics, spintronics, and quantum information processing. We use a cooled scanning probe microscope (SPM) to image and control an InAs quantum dot in an InAs/InP nanowire using the tip as a movable gate. Images of dot conductance vs tip position at T=4.2 K show concentric rings as electrons are added, starting with the first electron. The SPM can locate a dot along a nanowire and individually tune its charge, abilities that will be very useful for the control of coupled nanowire dots.
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| 3. |
- Chen, Wei, et al.
(författare)
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Energy structure and fluorescence of Eu2+ in ZnS:Eu nanoparticles
- 2000
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Ingår i: Physical Review B. - 1098-0121. ; 61:16, s. 11021-11024
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Tidskriftsartikel (refereegranskat)abstract
- Eu2+-doped ZnS nanoparticles with an average size of around 3 nm were prepared, and an emission band around 530 nm was observed. By heating in air at 150 degrees C, this emission decreased, while the typical sharp line emission of Eu3+ increased. This suggests that the emission around 530 nm is from intraion transition of Eu2+: In bulk ZnS:Eu2+, no intraion transition of Eu2+ was observed because the excited states of Eu2+ are degenerate with the continuum of the ZnS conduction band. We show that the band gap in ZnS:Eu2+ nanoparticles opens up due to quantum confinement, such that the conduction band of ZnS is higher than the first excited state of Eu2+, thus enabling the intraion transition of Eu2+ to occur.
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| 4. |
- Conache, Gabriela, et al.
(författare)
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Bias-controlled friction of InAs nanowires on a silicon nitride layer studied by atomic force microscopy
- 2010
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Ingår i: Physical Review B Condensed Matter. - College Park, Md. : American Physical Society. - 0163-1829 .- 1095-3795. ; 82:3
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Tidskriftsartikel (refereegranskat)abstract
- By studying how nanowires lying on a surface bend when pushed by an atomic force microscopy tip we are able to measure the friction between them and the substrate. Here, we show how the friction between InAs nanowires and an insulating silicon nitride layer varies when a dc voltage is applied to the tip during manipulation. The bias charges the capacitor formed by the wire and the grounded silicon back contact. Electrostatic forces increase the contact pressure and allow us to tune the friction between the wire and the silicon nitride surface. Using nanowires of about 40-70 nm diameter and a few microns in length we have applied biases in the range +12 to -12 V. A monotonic increase of the sliding friction with voltage was observed. This increase in friction with the normal force implies that the mesoscopic nanowire-surface system behaves like a macroscopic contact, despite the nanometer size of the contact in the direction of motion. The demonstrated bias-controlled friction has potential applications in MEMS/NEMS devices.
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| 5. |
- Ganjipour, Bahram, et al.
(författare)
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Transport studies of electron-hole and spin-orbit interaction in GaSb/InAsSb core-shell nanowire quantum dots
- 2015
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 91:16
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Tidskriftsartikel (refereegranskat)abstract
- We report low-temperature transport studies of parallel double quantum dots formed in GaSb/InAsSb core-shell nanowires. At negative gate voltages, regular patterns of Coulomb diamonds are observed in the charge stability diagrams, which we ascribe to single-hole tunneling through a quantum dot in the GaSb core. As the gate voltage increases, the measured charge stability diagram indicates the appearance of an additional quantum dot, which we suggest is an electron quantum dot formed in the InAsSb shell. We find that an electron-hole interaction induces shifts of transport resonances in the source-drain voltage from which an average electron-hole interaction strength of 2.9 +/- 0.3 meV is extracted. We also carry out magnetotransport measurements of a hole quantum dot in the GaSb core and extract level-dependent g factors and a spin-orbit interaction.
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| 6. |
- Håkanson, Ulf, et al.
(författare)
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Quantum-dot-induced ordering in GaxIn1-xP/InP islands
- 2002
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 66:23
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Tidskriftsartikel (refereegranskat)abstract
- Thin layers of GaxIn1-xP grown on top of self-assembled InP quantum dots has been studied using transmission electron microscopy (TEM), scanning tunneling microscopy (STM), and low-temperature scanning tunneling luminescence (STL). STM reveals that the overgrowth is highly uneven, in which elongated GaxIn1-xP islands covering the dots are formed. TEM and high-spatial-resolution STL show that the quantum dots locally induce domains with higher degree of ordering in the islands. The luminescence from these domains is observed as a strong GaxIn1-xP peak at an energy below the emission from the GaxIn1-xP barrier material.
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| 7. |
- Johansson, Mikael, et al.
(författare)
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Correlation between overgrowth morphology and optical properties of single self-assembled InP quantum dots
- 2003
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 68:12
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the early stages of GaInP overgrowth on InP quantum dots (QD's) experimentally and theoretically. A direct correlation between the surface morphology and the optical properties of individual InP QD's is made using scanning tunneling microscopy (STM) and scanning tunneling luminescence. The geometric structure of the islands is further investigated using cross-sectional transmission electron microscopy (TEM). The overgrowth occurs in three stages; initially the InP QD's act as seeding points for the overgrowth, where the GaInP grows laterally from the side facets of the QD. The growth occurs preferentially in the [110] direction and elongated GaInP/InP islands are formed. As the overgrowth continues the islands increase laterally in size and GaInP also starts to grow between the islands, but not covering the top of the InP QD's. The growth of GaInP on top of the QD's commences once the islands have begun to coalesce. Using a model based on the STM and TEM results the electronic structures of the QD's have been calculated by eight-band k.p theory. The calculations are in good agreement with the experimental results. Our findings unravel the details of the strain induced energy shift of the QD luminescence previously reported [Pistol , Appl. Phys. Lett. 67, 1438 (1995)].
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| 8. |
- Kristinsdottir, Liney Halla, et al.
(författare)
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Signatures of Wigner localization in epitaxially grown nanowires
- 2011
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 83:4
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Tidskriftsartikel (refereegranskat)abstract
- It was predicted by Wigner in 1934 that an electron gas will undergo a transition to a crystallized state when its density is very low. Whereas significant progress has been made toward the detection of electronic Wigner states, their clear and direct experimental verification still remains a challenge. Here we address signatures of Wigner molecule formation in the transport properties of InSb nanowire quantum-dot systems, where a few electrons may form localized states depending on the size of the dot (i.e., the electron density). Using a configuration interaction approach combined with an appropriate transport formalism, we are able to predict the transport properties of these systems, in excellent agreement with experimental data. We identify specific signatures of Wigner state formation, such as the strong suppression of the antiferromagnetic coupling, and are able to detect the onset of Wigner localization, both experimentally and theoretically, by studying different dot sizes.
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| 9. |
- Marlow, C. A., et al.
(författare)
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Unified model of fractal conductance fluctuations for diffusive and ballistic semiconductor devices
- 2006
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 73:19
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Tidskriftsartikel (refereegranskat)abstract
- We present an experimental comparison of magnetoconductance fluctuations measured in the ballistic, quasiballistic, and diffusive scattering regimes of semiconductor devices. In contradiction to expectations, we show that the spectral content of the magnetoconductance fluctuations exhibits an identical fractal behavior for these scattering regimes and that this behavior is remarkably insensitive to device boundary properties. We propose a unified model of fractal conductance fluctuations in the ballistic, quasiballistic, and diffusive transport regimes, in which the generic fractal behavior is generated by a subtle interplay between boundary and material-induced chaotic scattering events.
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| 10. |
- Martin, T P, et al.
(författare)
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Confinement properties of a Ga0.25In0.75As/InP quantum point contact
- 2008
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 77:15, s. 5-155309
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Tidskriftsartikel (refereegranskat)abstract
- We study the electrostatic confinement properties of a ballistic GaInAs nanostructure, a system with a high potential for quantum applications due to its small effective mass and persistence of quantum effects to higher temperatures. By measuring the magnetic depopulation of one-dimensional subbands in an etched quantum point contact, we demonstrate that the slope of the confinement at the Fermi level is an order of magnitude steeper than in surface-gated devices, indicating that this system is ideal for applications that are sensitive to the boundary geometry of devices. The subband spacing is found to range from 7 to 9.5 meV, which is significantly larger than previously reported for this material system.
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