| 1. |
- Dick Thelander, Kimberly, et al.
(författare)
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Height-controlled nanowire branches on nanotrees using a polymer mask
- 2007
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 18:3
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Tidskriftsartikel (refereegranskat)abstract
- The production of complex three-dimensional dendritic structures is an important step in the application of semiconductor nanowires. One promising method for achieving this is the sequential seeding of multiple generations of epitaxial nanowires using metal seed particles. However, it is difficult to control and predict the position of second and higher generation nanowires with respect to the first generation. Here we demonstrate a procedure for controlling the position of second-generation epitaxial nanowire branches on vertically aligned nanowire trunks. This method uses a spun-on polymer layer that masks first-generation wires to a specified height, preventing the growth of nanowire branches at lower positions as well as new nanowire growth on the substrate. This method appears not to be dependent on the materials or growth system (in this case MOVPE-grown GaP is demonstrated), and hence is likely to be applicable to a variety of materials systems and growth procedures using metal seed particles.
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| 2. |
- Dick Thelander, Kimberly, et al.
(författare)
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Improving InAs nanotree growth with composition-controlled Au-In nanoparticles
- 2006
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 17:5, s. 1344-1350
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Tidskriftsartikel (refereegranskat)abstract
- Au nanoparticles are commonly used as seeds for epitaxial growth of III-V semiconductor nanowires. However, the interaction between Au and In-containing III-V materials makes it difficult to control the growth of more complex nanowire structures in materials such as InAs. Here we report the growth of InAs nanowires and branched nanotrees using Au and Au-In nanoparticles. We show that the initial composition of the particle does not affect the morphology of the first-generation nanowires, nor does it affect the final composition of the particle after growth. However, when the Au-In particles were used to seed a second generation of nanowires, producing nanotrees, the branches exhibited a 2-3 times higher growth rate and more regular shape than those seeded by pure Au particles. This result is attributed to the decreased interaction between the seed particle and the trunk nanowires when Au-In particles are used. Thus the incorporation of In into the seed particle during particle production allows for modification of the particle-wire interaction.
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| 3. |
- Mikkelsen, Anders, et al.
(författare)
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The influence of lysine on InP(001) surface ordering and nanowire growth
- 2005
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 16:10, s. 2354-2359
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Tidskriftsartikel (refereegranskat)abstract
- We report on high resolution photoelectron core level spectroscopy (HRCLS) and scanning tunnelling microscopy (STM) measurements of the decomposition of lysine adsorbed on InP(001) substrates. We find that components from the lysine can be present on the InP surface even after annealing to 600 degrees C and desorption of the native surface oxide. We further observe that while a crystalline surface phase can be observed on the epi-ready surface after annealing, the lysine treated surface still appears rough. We conclude that lysine residues inhibit the formation of a flat crystalline structure on the InP(001) surface. These results are discussed in terms of the lysine promotion of [001] nanowire growth.
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| 4. |
- Mårtensson, Thomas, et al.
(författare)
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Fabrication of individually seeded nanowire arrays by vapour-liquid-solid growth
- 2003
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 14:12, s. 1255-1258
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Tidskriftsartikel (refereegranskat)abstract
- We report on a method of synthesizing arrays of individually seeded nanowires. An electron beam lithography and metal lift-off method was used to pattern InP(111)B substrates with catalysing gold particles. Vertical InP(111)B nanowire arrays were then grown from the gold particles, using metal-organic vapour phase epitaxy. The lithographic nature of the method allows individual control over each nanowire. Possible applications for such deterministic and uniform arrays include producing arrays of nanowire devices, two-dimensional photonic band gap structures and field emission displays, amongst others.
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| 5. |
- 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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| 6. |
- 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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| 7. |
- Svensson, CPT, et al.
(författare)
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Epitaxially grown GaP/GaAs1-xPx/GaP double heterostructure nanowires for optical applications
- 2005
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 16:6, s. 936-939
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate metal organic vapour phase epitaxy growth of GaP/GaAs1-xPx/GaP double heterostructure nanowires on GaP(111)B, and report bright photoluminescence at room temperature. By using different PH3 to AsH3 flow ratios during growth of the GaAs1-xPx segment, we are able to control the composition of the segment, making it feasible to tune the wavelength of the emitted light. A photoluminescence system was employed to characterize the luminescence, and x-ray energy dispersive spectrometry and x-ray diffraction studies were used to investigate the composition of the segment. These double heterostructure nanowires could in the future be used in optoelectronic devices and as multi pie-wavelength fluorescent markers for biomedical applications.
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| 8. |
- Borgström, Magnus, et al.
(författare)
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Arrays of Ge islands on Si(001) grown by means of electron-beam pre-patterning
- 2003
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484. ; 14:2, s. 264-267
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Tidskriftsartikel (refereegranskat)abstract
- We show that well-defined arrays of self-assembled Ge dots on Si(001) can be grown after pre-patterning the Si surface by means of an electron beam. The electron beam produces C-containing growth masks. The overgrowth of these masks with Si results in pits at the Si surface, in and around which Ge dots nucleate selectively. A manifold of different arrays can be obtained. Almost perfect arrays of quadruples of dots nucleate in the intersections of the four {11n} facets. This way of producing quantum dot arrays is very promising for producing dot structures suitable for use in the study of, for instance, dot-dot tunnelling and related effects.
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| 9. |
- Johansson, Jonas, et al.
(författare)
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Growth related aspects of epitaxial nanowires
- 2006
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Ingår i: Nanotechnology. - 0957-4484. ; 17:11, s. 355-361
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Tidskriftsartikel (refereegranskat)abstract
- We use metal - organic vapour phase epitaxy for growth investigations of epitaxial nanowires in III - V materials, such as GaAs, GaP, InAs, and InP. In this paper we focus on gold assisted growth of nanowires. The nature of the metal particle - whether it is in the solid or liquid state - is discussed. For InAs and InP we have demonstrated that gold assisted wires can only grow at temperatures where the particle is solid. We continue with a discussion concerning the kinetic aspects of nanowire growth. Under common growth conditions one observes that thinner wires grow faster than thicker wires, contrary to what was described in the early days of whisker growth. We address and resolve this discrepancy by discussing a simple transport model and comparing the supersaturations of different systems. Finally, we describe the morphology of epitaxial III - V nanowires with emphasis on the crystal structure.
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| 10. |
- Maximov, Ivan, et al.
(författare)
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Nanoimprint lithography for fabrication of three-terminal ballistic junctions in InP/GaInAs
- 2002
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484. ; 13:5, s. 666-668
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Tidskriftsartikel (refereegranskat)abstract
- We present processing technology and characterization results for InP/GaInAs two-dimensional electron gas (2DEG) three-terminal ballistic junction (TBJ) devices manufactured using nanoimprint lithography (NIL). To transfer sub-100 nm features into a high-mobility InP-based 2DEG material, we used SiO2/Si stamps made using electron beam lithography and reactive ion etching. After NIL, the resist residues are removed in oxygen plasma; this is followed by wet etching of InP/GaInAs to define the TBJ structures. Fabricated TBJ devices are characterized using scanning electron microscopy and electron transport measurements. Highly non-linear electrical characteristics as predicted by the theory (Xu H Q 2001 APPI. Phys. Lett. 78 2064) are demonstrated.
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