| 1. |
- Crowley, T.A., et al.
(författare)
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Synthesis of metal and metal oxide nanowires and nanotube arrays within a mesoporous silica template
- 2003
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 15:18, s. 3518-3522
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Tidskriftsartikel (refereegranskat)abstract
- Metallic nanowires of cobalt, copper, and iron oxide magnetite (Fe3O4) have been synthesized within the pores of mesoporous silica using a supercritical fluid inclusion technique. The mesoporous matrix provides a means of producing a high density of stable, hexagonally ordered arrays of highly crystalline nanowires. The formation of the metal and metal oxide nanowires within the silica mesopores was confirmed by transmission electron microscopy (TEM), N2 adsorption experiments, and powder X-ray diffraction (PXRD). The mechanism of nanowire formation within the mesopores appears to occur through the initial binding and coating of the pore walls with the metal atoms to form tubelike structures within the mesoporous template. The thickness of these tubes subsequently increases with further metal deposition until nanowires are formed. Additionally, the crystal structure of the cobalt nanowires formed within the mesoporous template can be readily changed by manipulating the density of the supercritical fluid phase.
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| 2. |
- Ziegler, K.J., et al.
(författare)
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Bistable nanoelectromechanical devices
- 2004
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 84:20, s. 4074-4076
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Tidskriftsartikel (refereegranskat)abstract
- A combined transmission electron microscopy-scanning tunneling microscopy (TEM-STM) technique has been used to investigate the force interactions of silicon and germanium nanowires with gold electrodes. The I(V) data obtained typically show linear behavior between the gold electrode and silicon nanowires at all contact points, whereas the linearity of I(V) curves obtained for germanium nanowires were dependent on the point of contact. Bistable silicon and germanium nanowire-based nanoelectromechanical programmable read-only memory (NEMPROM) devices were demonstrated by TEM-STM. These nonvolatile NEMPROM devices have switching potentials as low as 1 V and are highly stable making them ideal candidates for low-leakage electronic devices.
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| 3. |
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| 4. |
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| 5. |
- Erts, D., et al.
(författare)
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Semiconducting nanowires : properties and architectures
- 2004
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Ingår i: FUNCTIONAL NANOMATERIALS FOR OPTOELECTRONICS AND OTHER APPLICATIONS. - : TRANS TECH PUBLICATIONS LTD. ; , s. 109-115
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Konferensbidrag (refereegranskat)abstract
- One-dimensional quantum wires are expected to play important role in future electronic and optical devices. We have investigated semiconducting nanowires made by a novel supercritical fluid solution-phase technique [1]. Conductivity and force interactions in individual semiconductor nanowires were investigated by using an in-situ probing technique using a TEM-SPM [2,3], which is a combination of the scanning probe microscope (SPM) and the transmission electron microscope (TEM). Free standing Si nanowires were high resistive with exhibited metallic behaviour. Nonconductive gap was observed in Ge nanowires. The electromechanical properties of these wires were characterised and a prototype nanorelay was demonstrated. Uniform mesoporous thin films, with pores orientated almost perpendicular to the substrate surface are used as templates for unidirectional semiconducting nanowire growth. Structure of films and polycrystalline material containing Si and Ge nanowire arrays was investigated [4]. Luminescence of mesoporous nanowires was determined, as function of nanowire size. The optical properties can be controlled by the effective change of pore size inside mesoporous silica. Quantum-chemical simulation of the silicon nanowires is carried out by semi-empirical CLUSTER code.
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| 6. |
- Ziegler, K., et al.
(författare)
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The synthesis of matrices of embedded semiconducting nanowires
- 2004
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Ingår i: Faraday discussions. - : Royal Society of Chemistry (RSC). - 1359-6640 .- 1364-5498. ; 125, s. 311-326
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Tidskriftsartikel (refereegranskat)abstract
- In this work we report how single crystal nanowires can be assembled into regular arrays using mesoporous thin films to define the architecture. Mesoporous thin films were prepared by a sol-gel method. These provide films of very regular structure and dimensions. The films produced in this way have almost single crystal like structures and can also exhibit strong epitaxy to the underlying silicon substrate. The films are subjected to a supercritical fluid (SCF) environment in which a precursor is decomposed to yield nanowires of metals, semiconductors or oxides. Using these SCF conditions, pore filling is complete and the products are nanowires which are single crystals and structurally aligned in one direction. The growth mechanism of the nanowires is described and size effects discussed.
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| 7. |
- Andzane, J., et al.
(författare)
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Application of Tuning Fork Sensors for In-situ Studies of Dynamic Force Interactions Inside Scanning and Transmission Electron Microscopes
- 2012
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Ingår i: Medziagotyra. - : Kaunas University of Technology (KTU). - 1392-1320. ; 18:2, s. 197-201
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Tidskriftsartikel (refereegranskat)abstract
- Mechanical properties of nanoscale contacts have been probed in-situ by specially developed force sensor based on a quartz tuning fork resonator (TF). Additional control is provided by observation of process in scanning electron microscope (SEM) and transmission electron microscope (TEM). A piezoelectric manipulator allows precise positioning of atomic force microscope (AFM) probe in contact with another electrode and recording of the IF oscillation amplitude and phase while simultaneously visualizing the contact area in electron microscope. Electrostatic control of interaction between the electrodes is demonstrated during observation of the experiment in SEM. In the TEM system the TF sensor operated in shear force mode: Use of TEM allowed for direct control of separation between electrodes. New opportunities for in situ studies of nanomechanical systems using these instruments are discussed.
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| 8. |
- Andzane, J., et al.
(författare)
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Catalyst-free vapour-solid technique for deposition of Bi2Te3 and Bi2Se3 nanowires/nanobelts with topological insulator properties
- 2015
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 7:38, s. 15935-15944
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Tidskriftsartikel (refereegranskat)abstract
- We present a simple two-stage vapour-solid synthesis method for the growth of bismuth chalcogenide (Bi2Te3, Bi2Se3) topological insulator nanowires/nanobelts by using Bi2Se3 or Bi2Te3 powders as source materials. During the first stage of the synthesis process nanoplateteles, serving as "catalysts" for further nanowire/nanobelt growth, are formed. At a second stage of the synthesis, the introduction of a N-2 flow at 35 Torr pressure in the chamber induces the formation of free standing nanowires/nanobelts. The synthesised nanostructures demonstrate a layered single-crystalline structure and Bi : Se and Bi : Te ratios 40 : 60 at% for both Bi2Se3 and Bi2Te3 nanowires/nanobelts. The presence of Shubnikov de Haas oscillations in the longitudinal magneto-resistance of the nanowires/nanobelts and their specific angular dependence confirms the existence of 2D topological surface states in the synthesised nanostructures.
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| 9. |
- Andzane, Jana, et al.
(författare)
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Selection of Application Specific Single and Multi Walled Carbon Nanotubes by In Situ Characterization of Conductive and Field Emission Properties
- 2007
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Ingår i: AZojono - Journal of Nanotechnology online.
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Tidskriftsartikel (refereegranskat)abstract
- The conductive and field emission properties of individual single and multi-walled carbon nanotubes, grown by chemical vapour and supercritical fluid deposition techniques, have been assessed using an in-situ transmission electron microscope-scanning tunnelling microscope (TEM-STM) technique. The conductivity and field emission measurements were obtained from nanotube-electrode distance and contact observations. Experimental field emission characteristics for all carbon nanotubes investigated fitted well to the Fowler-Nordheim equation when different work functions were applied. Differences in field emission and conductive properties are analysed and related to the structure of the carbon nanotubes. The method presented here is suitable for in situ selection of CNT with desired properties for particular electronic applications.
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| 10. |
- Bogdanov, A. L., et al.
(författare)
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Fabrication of arrays of nanometer size test structures for scanning probe microscope tips characterization
- 1994
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Ingår i: Journal of Vacuum Science & Technology B: Microelectronics Processing and Phenomena. - : American Vacuum Society. - 0734-211X. ; 12:6, s. 3681-3684
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Konferensbidrag (refereegranskat)abstract
- A problem in scanning probe microscopy (SPM) is the unknown shape of the probing tip. Generally, the image is a convolution between the shape of the tip and the surface. Information of the shape of the probe may be gained by imaging very sharp tips. Here we present a method for making two-dimensional arrays of very sharp tips. The tip arrays were made of silicon using electron beam lithography with subsequent ion-beam etching. To achieve the best possible resolution, ultrasonic excitation was used during development of the bilayered PMMA resist. Thus, openings in the resist with size nearly equal to the spot size of the writing e-beam have been obtained. A further decrease of the radius of the tips was obtained by the choice of appropriate thickness for the masking NiCr layer. The tips were conical with a height up to 100 nm with a radius of the tip down to 10 nm. The tips were suitable for study of the shape of AFM probe tips, under condition that the tip array samples were rinsed in water prior to the measurement. Without the rinsing procedure, strong sticking forces between the probe and the sample would have eroded both of them. The regularity of the array provided an easy way to calibrate the lateral motion of the scanner
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| 11. |
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| 12. |
- de Graaf, Sebastian Erik, 1986, et al.
(författare)
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Direct Identification of Dilute Surface Spins on Al2 O3: Origin of Flux Noise in Quantum Circuits
- 2017
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 118:5, s. 057703-
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Tidskriftsartikel (refereegranskat)abstract
- An on-chip electron spin resonance technique is applied to reveal the nature and origin of surface spins on Al2O3. We measure a spin density of 2.2×1017 spins/m2, attributed to physisorbed atomic hydrogen and S=1/2 electron spin states on the surface. This is direct evidence for the nature of spins responsible for flux noise in quantum circuits, which has been an issue of interest for several decades. Our findings open up a new approach to the identification and controlled reduction of paramagnetic sources of noise and decoherence in superconducting quantum devices.
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| 13. |
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| 14. |
- Erts, D, et al.
(författare)
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Instrumentation of STM and AFM combined with transmission electron microscope
- 2001
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Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 72:7, s. 71-74
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Tidskriftsartikel (refereegranskat)abstract
- A scanning tunneling microscope (STM) combined with a transmission electron microscope (TEM) is a powerful tool for direct investigation of structures, electronic properties, and interactions at the atomic scale. Here, we report on two different designs of such TEM-STM as well as an extension with an atomic force microscope (TEM-AFM). In the first TEM-STM design, a stepper motor, combined with a one-dimensional inertial slider, was used to perform the coarse approach. The advantage of this design was the strong pulling force that enabled notched metallic wires to be broken inside the TEM, which lead to clean sample surfaces. A second design, with a three-dimensional inertial slider, allowed lateral motion inside the TEM, which simplified the adjustment of tip location on the sample. By replacing the STM tip with a standard AFM-cantilever chip, a new combination was demonstrated: TEM-AFM. Here the force was simply measured by direct TEM imaging of the motion of the AFM tip. Some experimental results are included to illustrate the capabilities of TEM-STM and TEM-AFM.
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| 15. |
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| 16. |
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| 17. |
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| 18. |
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| 19. |
- Hu, Q H, et al.
(författare)
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Properties of Tl-2201 thin films
- 1997
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Ingår i: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 282-287:Part 2, s. 1075-1076
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Tidskriftsartikel (refereegranskat)abstract
- Tl2Ba2CuO6 (Tl-2201) thin films were synthesised on single crystal LaAlO3 and SrTiO3 substrates and on bicrystal LaAlO3 by an ex-situ process. Depending on thallium content and processing conditions, the films were orthorhombic or tetragonal. Tc was in the range 30 – 92 K while Jc reached 4.106A/cm2 at 12 K. By oxygen depletion, Tc was increased by 15 – 20 K for some films.
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| 20. |
- Johansson, L G, et al.
(författare)
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Preparation and properties of Tl2Ba2CaCu2O8 thin films
- 1994
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Ingår i: Journal of Superconductivity. - 0896-1107 .- 1572-9605. ; 7:4, s. 767-771
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Tidskriftsartikel (refereegranskat)abstract
- Anex situ process has been developed to produce thin superconducting Tl2Ba2CaCu2O8 films. The properties of films grown on different substrates using different annealing regimes were studied. Critical temperatures of 103–107 K were measured on films prepared in a broad range of annealing temperatures on SrTiO3, LaAlO3, and Y-ZrO2 substrates. A critical current density,J c, of 2×106 A/cm2 at 77 K was measured on LaAlO3. Film morphology was studied by SEM, AFM, and STM.
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| 21. |
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| 22. |
- Kosmaca, J., et al.
(författare)
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Role of Nanoelectromechanical Switching in the Operation of Nanostructured Bi2Se3 Interlayers between Conductive Electrodes
- 2016
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Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 8:19, s. 12257-12262
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a simple low-cost method of preparation of layered devices for opto- and thermoelectric applications. The devices consist Of a functional Bi2Se3 layer of randomly oriented nanoplates and flexible nanobelts enclosed between two flat indium tin oxide (ITO) electrodes. The number of functional interconnections between the ITO electrodes and correspondingly the efficiency of the device can be increased by gradual nanoelectromechanical (NEM) switching of flexible individual Bi2Se3 nanobelts in the circuit. NEM switching is achieved through applying an external voltage to the device. For the first time, we investigate in situ NEM switching and breakdown parameters of Bi2Se3 nanobelts, visualize the processes occurring in the device under the influence of applied external voltage, and establish the limitations to the possible operational conditions.
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| 23. |
- Kunakova, Gunta, et al.
(författare)
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Bulk-free topological insulator Bi2Se3 nanoribbons with magnetotransport signatures of Dirac surface states
- 2018
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 10:41, s. 19595-19602
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 The Royal Society of Chemistry. Many applications of topological insulators (TIs) as well as new phenomena require devices with reduced dimensions. While much progress has been made to realize thin films of TIs with low bulk carrier densities, nanostructures have not yet been reported with similar properties, despite the fact that reduced dimensions should help diminish the contributions from bulk carriers. Here we demonstrate that Bi2Se3 nanoribbons, grown by a simple catalyst-free physical-vapour deposition, have inherently low bulk carrier densities, and can be further made bulk-free by thickness reduction, thus revealing the high mobility topological surface states. Magnetotransport and Hall conductance measurements, in single nanoribbons, show that at thicknesses below 30 nm, the bulk transport is completely suppressed which is supported by self-consistent band-bending calculations. The results highlight the importance of material growth and geometrical confinement to properly exploit the unique properties of topological surface states.
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| 24. |
- Kunakova, Gunta, 1987, et al.
(författare)
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Space charge limited current mechanism in Bi2S3 nanowires
- 2016
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 119:11
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Tidskriftsartikel (refereegranskat)abstract
- We report on the charge transport properties of individual Bi2S3 nanowires grown within the pores of anodized aluminum oxide templates. The mean pore diameter was 80 nm. Space charge limited current is the dominating conduction mechanism at temperatures below 160 K. Characteristic parameters of nanowires, such as trap concentration and trap characteristic energy, were estimated from current-voltage characteristics at several temperatures.
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| 25. |
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