| 1. |
- Håkanson, Ulf, et al.
(författare)
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Nano-aperture fabrication for single quantum dot spectroscopy
- 2003
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 14:6, s. 675-679
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Tidskriftsartikel (refereegranskat)abstract
- We present a simple and controllable method for fabricating nano-apertures in a metal film using polystyrene nano-spheres as masks during the metal evaporation. We show how the processing conditions used during deposition of the spheres such as spin velocity, nano-sphere concentration and a reduction of the surface tension interplay and control the distribution of spheres. The fabrication method is ideal for luminescence studies by isolating individual nanometre-sized objects, which is exemplified by photoluminescence spectroscopy of single self-assembled Stranski-Krastanow quantum dots.
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| 2. |
- Forsen, E, et al.
(författare)
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Fabrication of cantilever based mass sensors integrated with CMOS using direct write laser lithography on resist
- 2004
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 15:10, s. 628-633
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Tidskriftsartikel (refereegranskat)abstract
- A CMOS compatible direct write laser lithography technique has been developed for cantilever fabrication on pre-fabricated standard CMOS. We have developed cantilever based sensors for mass measurements in vacuum and air. The cantilever is actuated into lateral vibration by electrostatic excitation and the resonant frequency is detected by capacitive readout. The device is integrated on standard CMOS circuitry. In the work a new direct write laser lithography (DWL) technique is introduced. This laser lithography technique is based on direct laser writing on substrates coated with a resist bi-layer consisting of poly(methyl methacrylate) (PMMA) on lift-off resist (LOR). Laser writing evaporates the PMMA, exposing the LOR. A resist solvent is used to transfer the pattern down to the substrate. Metal lift-off followed by reactive ion etching is used for patterning the structural poly-Si layer in the CMOS. The developed laser lithography technique is compatible with resist exposure techniques such as electron beam lithography. We demonstrate the fabrication of sub-micrometre wide suspended cantilevers as well as metal lift-off with feature line widths down to approximately 500 nm.
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| 3. |
- Grant, Ann W., 1964, et al.
(författare)
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Transmission electron microscopy "windows" for nanofabricated structures
- 2004
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Ingår i: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 15:9, s. 1175-1181
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Tidskriftsartikel (refereegranskat)abstract
- We present the microfabrication of silicon nitride membrane supports ('windows') for transmission electron microscopy (TEM) and illustrate their usefulness for direct preparation and studies of nanostructures. These membrane 'windows' enable TEM to be incorporated as an affordable diagnostic tool in nanostructure fabrication and applications thereof, in an iterative fashion, both during and after preparation as well as subsequent experimental steps with the nanostructures, and even for real time in situ TEM observations. Several examples are shown, including protein adsorption and nanofabrication for applications in heterogeneous catalysis.
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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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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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| 6. |
- Thelander, Claes, et al.
(författare)
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AFM manipulation of carbon nanotubes: realization of ultra-fine nanoelectrodes
- 2002
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 13:1, s. 108-113
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the possibility of using carbon nanotubes as flexible, mobile electrical probes able to electrically contact nanometre- scaled objects. Configurations with metal electrodes evaporated on top of multi-, few- and single-wall carbon nanotubes have been studied. Scanning probe manipulation was used to create nano-mechanical switches by first cutting the various tubes, and then moving the parts back into electrical contact. We found multiwall tubes to be best suited as mobile probes, mainly due to their insensitivity to mechanical deformation. Finally, we present an example where the scanning probe manipulation technique has been used to electrically connect two carbon nanotubes to a 7 nm gold particle.
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| 7. |
- Whitlow, Harry J, et al.
(författare)
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Lithography of high spatial density biosensor structures with sub-100 nm spacing by MeV proton beam writing with minimal proximity effect
- 2004
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 15:1, s. 223-226
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Tidskriftsartikel (refereegranskat)abstract
- Metal electrode structures for biosensors with a high spatial density and similar to85 nm gaps have been produced using focused megaelectronvolt (MeV) proton beam writing of poly-(methyl methacrylate) positive resist combined with metal lift-off. The minimal proximity exposure and straight proton trajectories in (similar to100 nm) resist layers for focused MeV proton beam writing are strongly indicative that ultimate electrode gap widths approaching a few nanometres are achievable.
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| 8. |
- Zsebök, Otto, 1965, et al.
(författare)
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Morphology of InGaAs/GaAs quantum wires prepared by highly controlled deep-etching techniques
- 2001
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Ingår i: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 12, s. 32-7
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Tidskriftsartikel (refereegranskat)abstract
- Different types of InGaAs/GaAs deep-etched quantum wire (QWI) structure were successfully fabricated by high-energy electron beam lithography on GaAs(100) surfaces. A selective wet-chemical-etching technique, preceded by chemically assisted ion-beam etching, reduced the controlled lateral dimensions of the wires to ~10 nm due to strong under-etching. Various types of wire in the [011] and [011] crystallographic directions were prepared by the combined etching method. The side-walls of the wires were defined by the selectively etched low index crystallographic planes. A molecular-beam-epitaxy-grown graded InGaAs/GaAs quantum well was realized at the narrow `neck' region of the wires, thus providing the strongest possible lateral confinement of the QWI structure. Consequently, similarly to the selective growth of self-narrowing ridge structures, selective wet-chemical etching induced a controlled self-narrowing of the wire structures. Scanning electron microscopy images of the QWI nanostructures showed smooth side-walls defined by the crystallographic planes. Low-excitation photoluminescence spectroscopy of the structures revealed extremely high quantum efficiency and a size-dependent blue shift as a result of the strong lateral confinement
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| 9. |
- Berggren, Karl-Fredrik, et al.
(författare)
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On the role of electron exchange and correlation in semiconductor quantum dots
- 2001
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 12:4, s. 529-532
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Spontaneous magnetization of single and coupled quantum dots formed by lateral confinement of a high-mobility two-dimensional electron gas is studied for a realistic GaAs/AlGaAs heterostructure. The modelling of the device takes into account contributions from a patterned gate, doping, surface states, and mirror charges. To explore the magnetic properties we use the Kohn-Sham local spin-density formalism including the contributions from electron correlation and exchange. We show by explicit calculations that the exchange is the dominant mechanism driving a spontaneous magnetization of a dot. The correlation potential reduces the amount of level splitting and usually affects the electron content in the dot at a given gate voltage. These effects are, however, small and may be neglected under present circumstances. Single dots with up to 50 electrons have been studied.
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| 10. |
- Berggren, Karl-Fredrik, et al.
(författare)
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Quantum chaos among nodal points and streamlines at ballistic electron transport through open quantum dots
- 2001
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 12:4, s. 562-565
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We trace signatures of quantum chaos in the distribution of nodal points and streamlines for coherent electron transport through different types of quantum dots (chaotic and regular). We have calculated normalized distribution functions for the nearest distances between nodal points and found that this distribution may be used as a signature of quantum chaos for electron transport in open systems. Different chaotic billiards show the same characteristic distribution function for nodal points. This signature of quantum chaos is well reproduced using well known approaches for chaotic wavefunctions. We have also investigated the quantum flows which display some remarkable features.
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