Ion track

Summary

Ion tracks are damage-trails created by swift heavy ions penetrating through solids, which may be sufficiently-contiguous for chemical etching in a variety of crystalline, glassy, and/or polymeric solids. They are associated with cylindrical damage-regions several nanometers in diameter and can be studied by Rutherford backscattering spectrometry (RBS), transmission electron microscopy (TEM), small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS) or gas permeation. Ion track technology Ion track technology deals with the production and application of ion tracks in microtechnology and nanotechnology. Ion tracks can be selectively etched in many insulating solids, leading to cones or cylinders, down to 8 nanometers in diameter. Etched track cylinders can be used as filters, Coulter counter microchannels, be modified with monolayers, or be filled by electroplating. Ion track technology has been developed to fill certain niche

Official source

https://en.wikipedia.org/wiki/Ion_track

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One of revolutionary technologies to sequence single molecules, such as DNA, is using nanopore devices. A single-channel with nanometer-scale aperture allows an extremely rapid electric analysis of such single molecules. The objective of this work is to fabricate nanopores into robust, solid-state membranes to achieve better performances. The technological challenge is in the small required dimension of the nanopore, around 50-100 nm in diameter and depth. To reach this objective, we used two different techniques: the ion track technique and a microfabrication method associated with Focused Ion Beam (FIB). A literature review has been done on the ion track technique. Threshold values of the ion track formation have been found for different insulator materials (polymers, SiO2, SiN). We did experiments with the linear accelerator UNILAC (Universal Linear Accelerator) at the GSI (Darmstadt, Germany) where we irradiated our samples with heavy gold ions (11.4 MeV/nucleon). On very thin membranes, we expect that a direct perforation would occur, and we chose SiN membranes and SU-8 thin films as samples. However, the experiment of ion bombardment was not possible to be done early enough, thus TEM analysis have not been done yet. If the direct perforation by ion bombardment is not possible, a chemical etching step would be necessary. About the microfabrication method associated with Focused Ion Beam (FIB) perforation, we did experiments at the Center of Micro Nano Technology (CMI) in EPFL. First trial with FIB was done on SiN membranes. In order to obtain required aperture size, reduction of membrane thickness before perforation by FIB was attempted, but this process was difficult to be achieved because of charging. To overcome this dimension limitation we chose a silicon membrane. With silicon membranes, oxidation would be performed after perforation by FIB, since channel opening will be reduced by SiO2 growth. Moreover, this oxide layer allows a functionalisation of the inner surface of the nanopore by silane chemistry. That should improve the resolution of DNA analysis. Though the aperture size reduction by oxidation has not been done yet, refining and perforation by FIB will be done according to this idea. We should reach ca. 100 nm-aperture size. Even if validation measurements are not easy, our specifications should be reached with the oxidation. More experiments and analysis have to be performed for further improvement.

2004

Selective ion-induced grain growth: Thermal spike modeling and its experimental validation

Matteo Seita, Ralph Spolenak

Ion-bombardment-induced selective grain growth is a process that allows for full control of the orientation of vapor-deposited thin films, which can be converted from fiber-textured polycrystalline to single-crystal films. The main mechanisms behind this phenomenon are explained by a new thermal spike model, which takes into account and compares the different driving forces governing the film microstructure evolution upon irradiation and emphasizes the importance of the thermal spike shape and volume. The strong agreement between model and experimental data confirms that selective grain growth is driven by the minimization of the volume free energy. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Pergamon-Elsevier Science Ltd2013

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This paper reports on the technology development and characterization of polyimide-based, microfluidic channels with integrated nanoporous membranes. A layer transfer and lamination technique is used to fabricate flexible microchannels from spin-on polyimide. The microfluidic channels can be operated at high pressures and flow rates without leakage. Nanopores are created in the polyimide channel walls irradiation with swift heavy ions and subsequent chemical etching of the ion tracks. The irradiation and etching parameters can be used to adjust pore density (by ion fluence) and pore length (via ion energy). The track etching conditions, such as pH-value, concentration, temperature and etch time, define the pore diameter and pore geometry. Typical diameters of cylindrical pores range from 10 nm to 1 or 2 mum. The devices can be used for cross-flow filtration of particles and molecules in fluids or as bioimplants for drug delivery.

2002

2004