| 1. |
- Pankratov, Dmitry, et al.
(författare)
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Scalable, high performance, enzymatic cathodes based on nanoimprint lithography
- 2015
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Ingår i: Beilstein Journal of Nanotechnology. - : Beilstein Institut. - 2190-4286. ; 6, s. 1377-1384
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Tidskriftsartikel (refereegranskat)abstract
- Here we detail high performance, enzymatic electrodes for oxygen bio-electroreduction, which can be easily and reproducibly fabricated with industry-scale throughput. Planar and nanostructured electrodes were built on biocompatible, flexible polymer sheets, while nanoimprint lithography was used for electrode nanostructuring. To the best of our knowledge, this is one of the first reports concerning the usage of nanoimprint lithography for amperometric bioelectronic devices. The enzyme (Myrothecium verrucaria bilirubin oxidase) was immobilised on planar (control) and artificially nanostructured, gold electrodes by direct physical adsorption. The detailed electrochemical investigation of bioelectrodes was performed and the following parameters were obtained: open circuit voltage of approximately 0.75 V, and maximum bio-electrocatalytic current densities of 18 mu A/cm(2) and 58 mu A/cm(2) in air-saturated buffers versus 48 mu A/cm(2) and 186 mu A/cm(2) in oxygen-saturated buffers for planar and nanostructured electrodes, respectively. The half-deactivation times of planar and nanostructured biocathodes were measured to be 2 h and 14 h, respectively. The comparison of standard heterogeneous and bio-electrocatalytic rate constants showed that the improved bio-electrocatalytic performance of the nanostructured biocathodes compared to planar biodevices is due to the increased surface area of the nanostructured electrodes, whereas their improved operational stability is attributed to stabilisation of the enzyme inside nanocavities.
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| 2. |
- Pankratov, Dmitry, et al.
(författare)
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Transparent and flexible, nanostructured and mediatorless glucose/oxygen enzymatic fuel cells
- 2015
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 1873-2755 .- 0378-7753. ; 294, s. 501-506
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Tidskriftsartikel (refereegranskat)abstract
- Here we detail transparent, flexible, nanostructured, membrane-less and mediator-free glucose/oxygen enzymatic fuel cells, which can be reproducibly fabricated with industrial scale throughput. The electrodes were built on a biocompatible flexible polymer, while nanoimprint lithography was used for their nanostructuring. The electrodes were covered with gold, their surfaces were visualised using scanning electron and atomic force microscopies, and they were also studied spectrophotometrically and electrochemically. The enzymatic fuel cells were fabricated following our previous reports on membrane-less and mediator-free biodevices in which cellobiose dehydrogenase and bilirubin oxidase were used as anodic and cathodic biocatalysts, respectively. The following average characteristics of transparent and flexible biodevices operating in glucose and chloride containing neutral buffers were registered: 0.63 V open-circuit voltage, and 0.6 mu W cm(-2) maximal power density at a cell voltage of 0.35 V. A transparent and flexible enzymatic fuel cell could still deliver at least 0.5 mu W cm(-2) after 12 h of continuous operation. Thus, such biodevices can potentially be used as self-powered biosensors or electric power sources for smart electronic contact lenses. (C) 2015 Elsevier B.V. All rights reserved.
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| 3. |
- Ahvenniemi, Esko, et al.
(författare)
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Recommended reading list of early publications on atomic layer deposition-Outcome of the "Virtual Project on the History of ALD"
- 2017
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 35:1
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Forskningsöversikt (refereegranskat)abstract
- Atomic layer deposition (ALD), a gas-phase thin film deposition technique based on repeated, self-terminating gas-solid reactions, has become the method of choice in semiconductor manufacturing and many other technological areas for depositing thin conformal inorganic material layers for various applications. ALD has been discovered and developed independently, at least twice, under different names: atomic layer epitaxy (ALE) and molecular layering. ALE, dating back to 1974 in Finland, has been commonly known as the origin of ALD, while work done since the 1960s in the Soviet Union under the name "molecular layering" (and sometimes other names) has remained much less known. The virtual project on the history of ALD (VPHA) is a volunteer-based effort with open participation, set up to make the early days of ALD more transparent. In VPHA, started in July 2013, the target is to list, read and comment on all early ALD academic and patent literature up to 1986. VPHA has resulted in two essays and several presentations at international conferences. This paper, based on a poster presentation at the 16th International Conference on Atomic Layer Deposition in Dublin, Ireland, 2016, presents a recommended reading list of early ALD publications, created collectively by the VPHA participants through voting. The list contains 22 publications from Finland, Japan, Soviet Union, United Kingdom, and United States. Up to now, a balanced overview regarding the early history of ALD has been missing; the current list is an attempt to remedy this deficiency.
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| 4. |
- Fadil, Ahmed, et al.
(författare)
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Fabrication and improvement of nanopillar InGaN/GaN light-emitting diodes using nanosphere lithography
- 2015
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Ingår i: Journal of Nanophotonics. - 1934-2608. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Surface-patterning technologies have enabled the improvement of currently existing light-emitting diodes (LEDs) and can be used to overcome the issue of low quantum efficiency of green GaN-based LEDs. We have applied nanosphere lithography to fabricate nanopillars on InGaN/GaN quantum-well LEDs. By etching through the active region, it is possible to improve both the light extraction efficiency and, in addition, the internal quantum efficiency through the effects of lattice strain relaxation. Nanopillars of different sizes are fabricated and analyzed using Raman spectroscopy. We have shown that nanopillar LEDs can be significantly improved by applying a combination of ion-damage curing techniques, including thermal and acidic treatment, and have analyzed their effects using x-ray photoelectron spectroscopy. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)
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| 5. |
- Kauppinen, Christoffer, et al.
(författare)
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Atomic layer etching of gallium nitride (0001)
- 2017
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Ingår i: Journal of Vacuum Science and Technology A. - : American Vacuum Society. - 0734-2101. ; 35:6
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Tidskriftsartikel (refereegranskat)abstract
- In this work, atomic layer etching (ALE) of thin film Ga-polar GaN(0001) is reported in detail using sequential surface modification by Cl2 adsorption and removal of the modified surface layer by low energy Ar plasma exposure in a standard reactive ion etching system. The feasibility and reproducibility of the process are demonstrated by patterning GaN(0001) films by the ALE process using photoresist as an etch mask. The demonstrated ALE is deemed to be useful for the fabrication of nanoscale structures and high electron mobility transistors and expected to be adoptable for ALE of other materials.
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| 6. |
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| 7. |
- Khan, Sabbir Ahmed, et al.
(författare)
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High-Definition Nanoimprint Stamp Fabrication by Atomic Layer Etching
- 2018
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; , s. 2476-2482
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: Nanoimprint lithography (NIL) has the potential for low-cost andhigh-throughput nanoscale fabrication. However, the NIL quality and resolution areusually limited by the shape and size of the nanoimprint stamp features. Atomiclayer etching (ALE) can provide a damage-free pattern transfer with ultimate etchcontrol for features of all length scales, down to the atomic scale, and for all featuregeometries, which is required for good quality and high-resolution nanoimprintstamp fabrication. Here, we present an ALE process for nanoscale pattern transferand high-resolution nanoimprint stamp preparation. This ALE process is based onchemical adsorption of a monoatomic layer of dichloride (Cl2) on the siliconsurface, followed by the removal of a monolayer of Cl2-modified silicon by argonbombardment. The nanopatterns of different geometries, loadings, and pitcheswere fabricated by electron beam lithography on a silicon wafer, and ALE wassubsequently performed for pattern transfer using a resist as an etch mask. Thepost-ALE patterns allowed us to study the different effects and limitations of theprocess, such as trenching and sidewall tapering. The ALE-processed silicon wafers were used as hard nanoimprint stamps in a thermal nanoimprint process. Features as small as 30 nm were successfully transferred into a poly(methyl methacrylate) layer, which demonstrated the great potential of ALE in fabricating nanoimprint stamps with ultrahigh resolution.
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| 8. |
- Nebol'sin, Valery A., et al.
(författare)
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Capillary stability of vapor-liquid-solid crystallization processes and their comparison to Czochralski and Stepanov growth methods
- 2017
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 463, s. 46-53
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial semiconductor nanowires grown with vapor-liquid-solid crystallization processes are very attractive nanoscale objects for many different applications. Despite extensive studies of the growth mechanism, there is still a lack of understanding of the growth process; in particular, the stability of the vapor-liquid-solid crystallization process has not previously been studied. Here we examine the capillary stability of the vapor-liquid-solid growth of nanowires and filamentary crystals with different diameters and demonstrate that the growth is stable for small Bond numbers when the meniscus height is linearly dependent on catalyst diameter. The capillary stability of vapor-liquid-solid growth is also compared with capillary stability in the Stepanov and Czochralski crystal growth methods; it is shown that capillary stability is not possible in the Czochralski method, although it is possible in the Stepanov growth method when the ratio of crystal diameter to shaper diameter is >1/2. These findings are important for better understanding and improved control of the growth of nanowires and filamentary crystals and indicate, for example, that large diameter filamentary crystals can be grown via a vapor-liquid-solid mechanism if the influence of gravity forces on the liquid catalytic particle shape can be reduced.
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| 9. |
- Nebol'sin, Valery A., et al.
(författare)
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Thermodynamics of oxidation and reduction during the growth of metal catalyzed silicon nanowires
- 2019
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 505, s. 52-58
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the thermodynamics of oxide formation, and the recovery of silicon and the metal catalysts from the dissociation of their respective oxides during the growth process of Si nanowires (NWs) under the Vapor → Liquid Droplet → Solid (VLS) mechanism. It is demonstrated that Si NWs under growth temperatures are thermodynamically unstable in any gas phase containing even a small concentration of O2, and under favorable kinetic conditions Si NWs should entirely convert into dioxide (SiO2). Thermal dissociation of SiO2 in the growth conditions for NWs is practically impossible as it would require either lowering the pressure of O2 to an unachievable, critically low value or raising the temperature to a point which is impossible to reach in ordinary conditions. Decreasing the diameter, i.e., increasing the Si NW dispersity, leads to an increase in the interaction with O2 and this O2 will be held more tightly by Si. Thus, thinner NWs should oxidize stronger than thicker ones. The main metal catalysts for NW growth, as well as Si, are characterized by significant affinity with O2 and inconvertible oxide formation reactions. The most stable Si NW growth is observed with metals (Au, Pt, Cu, Ni, etc.) whose oxides are less stable than SiO2. Only metals with a lower affinity to O2 than to H2 or any other reducing agent are applicable to guarantee the recovery process when used as a catalyst for the growth of NWs.
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| 10. |
- Pettersson, Håkan, 1962-, et al.
(författare)
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Assembling ferromagnetic single-electron transistors with atomic force microscopy
- 2016. - 2
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Ingår i: Nanostructures in Electronics and Photonics. - London : Pan Stanford Publishing. - 9789814241120 - 9789814241106 ; , s. 29-40
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Ferromagnetic Single Electron Transistors (F-SETs) comprise ferromagnetic electrodes connected to a ferromagnetic- or non-magnetic central island via tunnel barriers. These devices are important for studies of spin-transport physics in confined structures. Here we describe the development of a novel type of AFMassembled nano-scale F-SETs suitable for spin-transport investigations at temperatures above 4.2 K. The ingenious fabrication technique means that their electrical characteristics can be tuned in real-time during the fabrication sequence by re-positioning the central island with Ångström precision. © 2008 by Taylor & Francis Group, LLC.
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