| 1. |
- Xu, Tao, et al.
(författare)
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Faceting, composition and crystal phase evolution in III-V antimonide nanowire heterostructures revealed by combining microscopy techniques
- 2012
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 23:9
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Tidskriftsartikel (refereegranskat)abstract
- III-V antimonide nanowires are among the most interesting semiconductors for transport physics, nanoelectronics and long-wavelength optoelectronic devices due to their optimal material properties. In order to investigate their complex crystal structure evolution, faceting and composition, we report a combined scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanning tunneling microscopy (STM) study of gold-nucleated ternary InAs/InAs1-xSbx nanowire heterostructures grown by molecular beam epitaxy. SEM showed the general morphology and faceting, TEM revealed the internal crystal structure and ternary compositions, while STM was successfully applied to characterize the oxide-free nanowire sidewalls, in terms of nanofaceting morphology, atomic structure and surface composition. The complementary use of these techniques allows for correlation of the morphological and structural properties of the nanowires with the amount of Sb incorporated during growth. The addition of even a minute amount of Sb to InAs changes the crystal structure from perfect wurtzite to perfect zinc blende, via intermediate stacking fault and pseudo-periodic twinning regimes. Moreover, the addition of Sb during the axial growth of InAs/InAs1-xSbx heterostructure nanowires causes a significant conformal lateral overgrowth on both segments, leading to the spontaneous formation of a core-shell structure, with an Sb-rich shell.
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| 2. |
- Astromskas, Gvidas, et al.
(författare)
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Doping Incorporation in InAs nanowires characterized by capacitance measurements
- 2010
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 108
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Tidskriftsartikel (refereegranskat)abstract
- Sn and Se doped InAs nanowires are characterized using a capacitance-voltage technique where the threshold voltages of nanowire capacitors with different diameter are determined and analyzed using an improved radial metal-insulator-semiconductor field-effect transistor model. This allows for a separation of doping in the core of the nanowire from the surface charge at the side facets of the nanowire. The data show that the doping level in the InAs nanowire can be controlled on the level between 2×1018 to 1×1019 cm−3, while the surface charge density exceeds 5×1012 cm−2 and is shown to increase with higher dopant precursor molar fraction.
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| 3. |
- Astromskas, Gvidas, et al.
(författare)
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Temperature and frequency characterization of InAs nanowire and HfO2 interface using capacitance-voltage method
- 2011
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Ingår i: Microelectronic Engineering. - : Elsevier BV. - 1873-5568 .- 0167-9317. ; 88:4, s. 444-447
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Konferensbidrag (refereegranskat)abstract
- InAs/HfO2 nanowire capacitors using capacitance-voltage (CV) measurements are investigated in the range of 10 kHz to 10 MHz. The capacitors are based on vertical nanowire arrays that are coated with an 8 nm-thick HfO2 layer by atomic layer deposition. CV characteristics are measured at temperatures in the range between -140 and 40 degrees C and the CV characteristics for nanowires with different Sn and Se n-type doping levels are compared. The comparison of the data at various doping levels points towards large number of traps for highly doped samples, caused by the preferential dopant precursor incorporation at the nanowire surface. We also evaluate the frequency dispersion of the accumulation capacitance and determine values below 2% with weak temperature dependence, indicating the existence of border traps in these nanowire capacitors. (C) 2010 Elsevier B.V. All rights reserved.
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| 4. |
- Astromskas, Gvidas, et al.
(författare)
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Temperature dependence of GaSb overgrowth of tungsten on GaSb (001) substrates using MOVPE
- 2008
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Ingår i: 20th International Conference on Indium Phosphide and Related Materials, 2008. IPRM 2008. - 1092-8669. ; , s. 354-356
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Konferensbidrag (refereegranskat)abstract
- We demonstrate GaSb overgrowth over tungsten patterns and that selective area epitaxy is achievable in the W/GaSb system. By controlling the facet growth at low temperatures, it is possible to embed a metal grating in a thin layer.
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| 5. |
- Berg, Alexander, et al.
(författare)
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Growth and optical properties of InxGa1−xP nanowires synthesized by selective-area epitaxy
- 2017
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Ingår i: Nano Research. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 10:2, s. 672-682
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Tidskriftsartikel (refereegranskat)abstract
- Ternary III–V nanowires (NWs) cover a wide range of wavelengths in the solar spectrum and would greatly benefit from being synthesized as position-controlled arrays for improved vertical yield, reproducibility, and tunable optical absorption. Here, we report on successful selective-area epitaxy of metal-particle-free vertical InxGa1−xP NW arrays using metal–organic vapor phase epitaxy and detail their optical properties. A systematic growth study establishes the range of suitable growth parameters to obtain uniform NW growth over a large array. The optical properties of the NWs were characterized by room-temperature cathodoluminescence spectroscopy. Tunability of the emission wavelength from 870 nm to approximately 800 nm was achieved. Transmission electron microscopy and energy dispersive X-ray measurements performed on cross-section samples revealed a pure wurtzite crystal structure with very few stacking faults and a slight composition gradient along the NW growth axis. [Figure not available: see fulltext.]
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| 6. |
- 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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| 7. |
- Borg, Mattias, et al.
(författare)
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Characterization of GaSb nanowires grown by MOVPE
- 2008
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Ingår i: Journal of Chrystal Growth. - : Elsevier BV. - 0022-0248. ; 310:23, s. 5119-5122
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Konferensbidrag (refereegranskat)abstract
- We report the growth and characterization of GaSb nanowires grown by MOVPE. The structural properties of the nanowires are investigated by the means of transmission electron microscopy, X-ray diffraction and single nanowire photoluminescence. The measurements confirm a high material quality in the GaSb nanowires. Also, a back-gated nanowire transistor structure is used to extract values for the polarity and resistivity of the GaSb. Finally, a simple kinetic model is presented to explain the non-linear time dependence of the GaSb nanowire growth. (C) 2008 Elsevier B.V. All rights reserved.
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| 8. |
- Borg, Mattias, et al.
(författare)
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GaAs/GaSb nanowire heterostructures grown by MOVPE
- 2008
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 310:18, s. 4115-4121
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Tidskriftsartikel (refereegranskat)abstract
- We report Au-assisted growth of GaAs/GaSb nanowire heterostructures on GaAs(1 1 1)B-substrates by metal-organic vapor phase epitaxy. The growth is studied at various precursor molar fractions and temperatures, in order to optimize the growth conditions for the GaSb nanowire segment. In contrast to most other III-V nanowire systems, the GaSb nanowire growth is Group V-limited under most conditions. We found that depending on the TMSb molar fraction, the seed particle is either supersaturated AuGa or AuGa2 during GaSb growth. The high Ga content in the particle gives a characteristic diameter increase between the GaAs and GaSb segment. From TEM and XEDS measurements we conclude that the GaSb nanowire growth occurs along either the AuGa-GaSb or AuGa2-GaSb pseudo-binaries of the Au-Ga-Sb ternary phase diagram. Finally, the GaSb nanowires exhibit untapered radial growth on the {1 (1) over bar 0} side facets. (C) 2008 Elsevier B.V. All rights reserved.
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| 9. |
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| 10. |
- Borg, Mattias, et al.
(författare)
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MOVPE Growth and Structural Characterization of Extremely Lattice-Mismatched InP-InSB Nanowire Heterostructures
- 2009
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Ingår i: 2009 IEEE 21st International Conference On Indium Phosphide & Related Materials (IPRM). - 1092-8669. ; , s. 249-252
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Konferensbidrag (refereegranskat)abstract
- We present a growth study and structural characterization of InP-InSb nanowire heterostructures. In contrast to planar epitaxy, this heterostructure can be realized in nanowires without the formation of dislocations, despite an extreme lattice-mismatch (10.4%). We obtain high crystal quality in the InSb nanowires, confirmed by a narrow 111 reflection peak measured by XRD. Additionally, the diameter dependence of the nanowire growth rate was investigated. An original competition between surface growth and nanowire growth is found, which can be controlled by varying the nanowire surface coverage. Finally, HRTEM and X-EDS investigations reveal that the InSb nanowire is always defect-free zinc-blende, and that the InP-InSb heterointerface is free from misfit dislocations, although single twin planes are common.
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