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Ion Tracks for Micro- and Nanofabrication: From Single Channels to Superhydrophobic Surfaces
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A method is described for preset-count irradiations between 1 and 100 ions singling-out individual ions from an ion beam with more than a billion ions arriving per second. The ion tracks are etched in a conductometric system with real-time evaluation of the acquired data. The etch process can be interrupted when reaching a preset channel diameter. Cylindrical channels are obtained by adding surfactants to the etch solution forming a self-assembled barrier between etching medium and polymer. Asymmetric etching of single ion tracks leads to pH sensitive conical pores with diode-like properties. Using etched channels as template, homogeneous and multilayer magnetic single-wires are electrodeposited. The magnetoresistivity of the wires is studied. Single-track applications comprise critical apertures (cylindric, conic, necked), asymmetric pores (pH sensitive, biospecific), Giant Magneto Resistance sensors, and spintronic devices.

On the basis of studies with individual ion tracks we tackled tilted multiporous systems such as ion beam lithography with a masked ion beam leading to micro-structures with inclined walls and anisotropic superhydrophobic ion track textures, analogous to biological shingle structures on butterfly wings. We demonstrated qualitatively, that the asymmetry of the texture translates into motion under ultrasonic agitation. This could lead to the development of rotary drives.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2010. , 63 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 700
Keyword [en]
Ion track, single ion, real time, phase detection, conductometric cell, conductometry, electro replication, microtechnology, nanotechnology, surfactant, self organization, GMR, magnetic, sensor technology, hydrophobic, tilted texture.
National Category
Physical Sciences
Research subject
Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-111247ISBN: 978-91-554-7683-0 (print)OAI: oai:DiVA.org:uu-111247DiVA: diva2:280068
Public defence
2010-01-29, Polhemsaalen, Ångström Laboratorium, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2010-01-07 Created: 2009-12-08 Last updated: 2010-01-15
List of papers
1. Controlled fabrication of ion track nanowires and channels
Open this publication in new window or tab >>Controlled fabrication of ion track nanowires and channels
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2010 (English)In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, Vol. 268, no 6, 676-686 p.Article in journal (Refereed) Published
Abstract [en]

We describe a system for fabricating prescribed numbers of ion track nanochannels and nanowires from a few hundred down to one. It consists of two parts: First, a mobile TAPE TRANSPORT SYSTEM, which, in connection with an ion beam from a heavy-ion accelerator (nuclear charge Z above 18 and specific energy between 1 and 10 MeV/nucleon) tuned down to low flux density by means of defocusing and a set of sensitive fluorescence screens, can fabricate a series of equidistant irradiation spots on a tape, whereby each spot corresponds to a preset number of ion tracks. The tape transport system uses films of 36 mm width and thicknesses between 5 and 100 µm. The aiming precision of the system depends on the diameter of the installed beam defining aperture, which is between 50 and 500 µm. The distance between neighboring irradiation spots on the tape is variable and typically set to 25 mm. After reaching the preset number of ion counts the irradiation is terminated, the tape is marked and moved to the next position. The irradiated frames are punched out to circular membranes with the irradiation spot in the center. The second part of the setup is a compact CONDUCTOMETRIC SYSTEM with 10 picoampere resolution consisting of a computer controlled conductometric cell, sealing the membrane hermetically between two chemically inert half-chambers containing electrodes and filling/flushing openings, and is encased by an electrical shield and a thermal insulation. The ion tracks can be etched to a preset diameter and the system can be programmed to electroreplicate nanochannels in a prescribed sequence of magnetic/nonmagnetic metals, alloys or semiconductors. The goal of our article is to make the scientific community aware of the special features of single ion fabrication and to demonstrate convincingly the significance of controlled etching and electroreplication.

Keyword
conductometry, conductometric cell, electrodeposition, micro and nanofabrication, GMR, ion track technology, magnetoelectronics, nanowires, phase detection, real-time control, self-organization, sensor-technology, single-ion, spintronics, surfactant
National Category
Engineering and Technology
Research subject
Physics; Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-112206 (URN)10.1016/j.nimb.2009.12.017 (DOI)000276053700021 ()
Available from: 2010-01-11 Created: 2010-01-11 Last updated: 2011-02-25Bibliographically approved
2. Diode-like single-ion track membrane prepared by electro-stopping
Open this publication in new window or tab >>Diode-like single-ion track membrane prepared by electro-stopping
2001 (English)Article in journal (Refereed) Published
Abstract [en]

The prepn. of an asym. membrane in poly(ethylene terephthalate) (PET) is described, using a combination of chem. and electro-stopping. For this purpose, a single-ion-irradiated PET film is inserted into an electrolytic cell and etched from one side in 9 M sodium hydroxide while bathing the other side in a mixt. of 2 M KCl and 2 M HCOOH (1:1 by vol.), elec. retracting the OH- ions from the tip of the etch pit during pore break-through. When a preset current has been reached, the etch process is interrupted by replacing the etching soln. with acidic 1 M potassium chloride soln. After etching, the current-voltage (I-V) characteristic is detd. under sym. bathing conditions, immersing both sides of the membrane in KCl solns. of identical concn. (0.01-1 M) and pH (3-8). The I-V characteristic is strongly non-linear, comparable to that of an elec. diode. If the polarity during etching is reversed, pushing the OH- ions into the tip of the etch pit, the resulting pores are larger and the degree of asymmetry smaller. The importance of electro-stopping is compared with chem. stopping.

Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-111265 (URN)
Available from: 2010-01-11 Created: 2009-12-08 Last updated: 2011-01-17
3. Influence of a surfactant on single ion track etching: preparing and manipulating cylindrical micro wires
Open this publication in new window or tab >>Influence of a surfactant on single ion track etching: preparing and manipulating cylindrical micro wires
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2007 (English)In: Nuclear Instruments and Methods in Physics Reseach B, ISSN 0168-583X, Vol. 265, no 2, 621-625 p.Article in journal (Refereed) Published
Abstract [en]

The influence of the alkali resistant surfactant Dowfax 2A1 on single ion track etching in 30 μm polycarbonate foils is studied at low etch rate (5 M NaOH at 41.5 ± 2 °C) using electro conductivity measurements. At surfactant concentrations above 10−4 vol.% break-through times are predictable (Δt/t < 0.25). At high surfactant concentrations (0.1 vol.%) the formation of cylindrical channels is favoured. The shape of these channels (length  26 μm, diameter  1.8 μm) is verified by electro-replication and SEM observation of the resulting wires. Agreement of radii is better than 0.1 μm. Depending on the current limit set during electro replication compact or hollow cylinders can be obtained. A technique for localizing and manipulating individual micro wires by their head buds is described.

Keyword
Micro channel, Nano channel, Electro conduction, Cylinder, Track etching, Ion track, Real-time measurement, Electro replication, Micro wire, Micro tube, Nano wire, Surfactant interaction
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-16432 (URN)10.1016/j.nimb.2007.09.029 (DOI)000252001800024 ()
Available from: 2008-05-23 Created: 2008-05-23 Last updated: 2011-01-17Bibliographically approved
4. Electrodeposition of cobalt based ferro-magnetic metal nanowires in polycarbonate films with cylindrical nanochannels fabricated by heavy-ion-track etching
Open this publication in new window or tab >>Electrodeposition of cobalt based ferro-magnetic metal nanowires in polycarbonate films with cylindrical nanochannels fabricated by heavy-ion-track etching
2008 (English)In: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 38, no 5, 713-719 p.Article in journal (Refereed) Published
Abstract [en]

Polycarbonate films of thickness 30 mu m were irradiated with heavy ions by applying a flux of 10(8) ions cm(-2) to produce straight tracks perpendicular to the film surface. The tracks were preferentially etched in 6 M aqueous solution of sodium hydroxide to prepare cylindrical nanochannels. The channel diameters were tuned between 200 and 600 nm by varying the etching time. Co81Cu19 alloy nanowires were electrodeposited potentiostatically, while Co/Cu multilayered nanowires, consisting of alternating Co and Cu layers with thickness 10 nm, were synthesized by means of a pulse plating technique in channels of length 30 mu m and diameter 200 nm. Co81Cu19 alloy nanowires showed an anisotropic magnetoresistance effect of 0.6%, and the giant magnetoresistance of Co/Cu multilayered nanowires reached up to 8.0%.

Keyword
heavy ion, polycarbonate, electrodeposition, cobalt, copper, nanochannel
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-110440 (URN)10.1007/s10800-008-9499-1 (DOI)000254804700017 ()
Available from: 2009-11-16 Created: 2009-11-16 Last updated: 2016-04-13Bibliographically approved
5. Current perpendicular to plane single-nanowire GMR sensor
Open this publication in new window or tab >>Current perpendicular to plane single-nanowire GMR sensor
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2007 (English)In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 86, no 1, 43-47 p.Article in journal (Refereed) Published
Abstract [en]

By electrochemical deposition in a single nanopore membrane we fabricate Cu/Co layered single nanowires, that exhibit up to 10% magnetoresistance at room temperature. Single nanopore membranes are prepared by irradiating polycarbonate membranes with exactly one swift heavy ion, and by subsequent chemical etching of the single ion track. Both dc and pulsed electrodeposition of single wires consisting of Cu-Co alloy and Cu/Co multilayers respectively, are performed from a bath containing the two metal ions. By sputtering a gold electrode on the upper membrane surface, the single nanowire embedded in the flexible polymer foil is reliably contacted. While alloy wires exhibit anisotropic magnetoresistance (AMR), multilayer wires display current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) behavior. This demonstrates that both the fabrication and contacting methods are very suitable for the investigation of transport properties, without the necessity of lithographic processes and without manipulation of the nanowires. In addition, the method opens up many new possibilities for single nanowire-based sensors.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-25856 (URN)10.1007/s00339-006-3738-2 (DOI)000242013700006 ()
Available from: 2007-02-15 Created: 2007-02-15 Last updated: 2011-05-13Bibliographically approved
6. Magneto-sensitive nickel nanowires fabricated by electrodeposition into multi- and single-ion track templates
Open this publication in new window or tab >>Magneto-sensitive nickel nanowires fabricated by electrodeposition into multi- and single-ion track templates
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2006 (English)In: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 36, no 10, 1157-1162 p.Article in journal (Refereed) Published
Abstract [en]

Polycarbonate templates of ( 30 +/- 1) mu m thickness containing cylindrical etched-track nanochannels of ( 500 +/- 50) nm diameter were used for electrodeposition of Ni nanowires. Using 10(4) channels per cm(2), the most favourable deposition potential of -1.0 V was determined in a potentiostatic mode by varying the deposition potential with respect to an Ag/AgCl reference electrode over a range between -0.1 V and -1.5 V. The deposition efficiency at -1.0 V was estimated around 10%. The resulting single wires had a resistance around 200 W and showed an anisotropic magnetoresistance (AMR) effect of 1%, applicable to directionally sensitive magnetic field sensors.

Keyword
electrodeposition, ion beam, magnetoresistance, nanochannel, nickel, polycarbonate
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-22393 (URN)10.1007/s10800-006-9200-5 (DOI)000240514700012 ()
Available from: 2007-02-14 Created: 2007-02-14 Last updated: 2011-06-17Bibliographically approved
7. Stroke Asymmetry of Tilted Superhydrophobic Ion Track Textures
Open this publication in new window or tab >>Stroke Asymmetry of Tilted Superhydrophobic Ion Track Textures
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2010 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 9, 6790-6796 p.Article in journal (Refereed) Published
Abstract [en]

The stroke asymmetry of contact tingles of water drops on tilted hydrophobic textures is demonstrated, obtained by ion track etching followed by a hydrophobic treatment. Preliminary trends concerning the advancing and receding contact angles are established, each with and against stroke direction. In rough agreement with Cassie-Baxter theory, the cosines of these four contact angles depend linearly on the wetted area fraction. The etched tracks are randomly distributed on the surface of polycarbonate disks and inclined by 300 with respect to the surface, whereby the aspect ratio of individual etched cones is larger than 10. The morphology of the resulting surface is characterized by randomly shaped flat tops overhanging on one side and gradually falling off on the other side. The area fraction of the supporting tops can be calculated from the number of impinging ions per unit area and the cross section of the etched ion tracks. The top layer of the texture consists of flat, horizontal, irregularly shaped tops supporting water drops in the Cassie-Baxter state. With increasing etching time, the texture becomes increasingly defied. To fabricate the textures, we irradiated polyearbonate with 5 x 10(7) Br-80(7+) ions/cm(2) of 30 MeV total energy (having a range of about 20 mu m in polycarbonate) at a tilt angle of 30 with respect to the sample surface and etched the latent ion tracks selectively. The textured surface is made hydrophobic by carbondifluoride radicals (CF2) resulting from the decay of octafluorocyclobutane, C4F8, in a plasma reactor. The goal of the report is to show that the tilt orientation of a superhydrophobic surface leads to advancing and receding contact angles depending on the orientation with and against the stroke direction. In addition, a rotating movement is demonstrated qualitatively by floating a rotationally asymmetric disk on an ultrasonic bath, similarly treated after an irradiation with (1.2 +/- 0.4) x 10(7) Xe-129(274) MeV/cm- of 8.3 MeV/nucleon at an angle of 45 degrees, whereby the superhydrophobic side of the disk points downward to the water of the ultrasonic bath.

National Category
Engineering and Technology Physical Sciences
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-111270 (URN)10.1021/la904137t (DOI)000276969700105 ()
Available from: 2010-01-11 Created: 2009-12-08 Last updated: 2016-04-19

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