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Nanopore Structures and Their Applications
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
Siwy et al. demonstrated the creation of a nanopore structure in polyimide using ion-track etching.13 First, a sample of stacked polyimide foils (12.5 μm in thickness) was irradiated by heavy ions (uranium at 2,640 MeV) using a metallic mask to ensure the ions accessed only the desired area. Note that UV irradiation of the sample is performed before chemical etching to increase the sensitivity of the etching.12 After irradiation, ion-track etching using sodium hypochlorite (NaOCl) was carried out at 50°C, where the specific temperature was selected to optimize the effectiveness of both ion-track etching and NaOCl decomposition. The NaOCl solution was at 12.6 pH and had an active chlorine (Cl) content of 13%. The ion-track etching was performed between two compartments filled with NaOCl and KI. The 2I- in the stopping solution reacted with OCl-ions in the etching solution, reducing OCl- to Cl- according to the reaction: OCl−+2H++2I−→I2+Cl−+H2O
Microchips and Methods for the Characterization of Thermoelectric Transport Properties of Nanostructures
Published in D. M. Rowe, Materials, Preparation, and Characterization in Thermoelectrics, 2017
Friedemann Völklein, Daniel Huzel, Heiko Reith, Matthias Schmitt
The steps of nanowire fabrication by ion-track technology are represented in Figure 22.1. A high-energetic ion beam, consisting of 11.4 MeV/nucleon Au26+ or Pb26+ ions, strikes a 30-µm-thick polycarbonate membrane (foil) and generates latent tracks. These tracks are chemically etched in aqueous sodium hydroxide leading to the formation of nanochannels whose diameter is controlled by the etching parameters (concentration, temperature, etching time). After deposition of a metal layer on one of the membrane surfaces, the channels are electrochemically filled with Bi, Bi1−xSbx or Bi2Te3. Free-standing nanowires are created by dissolving the matrix in an organic solvent. Subsequently, the nanowires are detached from the back electrode by ultrasonication. After this process step, nanowires with lengths ranging from a few to 30 µm are available in the suspension. The wires are deposited on a substrate of choice (e.g., on a silicon wafer with SiO2 film) by applying a few drops of the solvent containing the needles. The solvent evaporates within a few minutes leaving behind randomly distributed wires. By controlling the fabrication parameters, polycrystalline as well as single-crystalline wires can be created [14–16]. Figure 22.2 presents a scanning electron microscopy (SEM) image, demonstrating smooth wire contours and narrow diameter distribution.
Interaction of Radiation with Semiconductor Devices
Published in John D. Cressler, H. Alan Mantooth, Extreme Environment Electronics, 2017
Galloway Kenneth F., Schrimpf Ronald D.
Single-event burnout (SEB) and single-event gate rupture (SEGR) of power MOSFETs are catastrophic failure mechanisms that are initiated by the passage of a heavy ion through sensitive regions of the device structure. Power BJTs are susceptible to SEB as well. SEB of power MOSFETs was first reported by Waskiewicz et al. [67], SEB of power BJTs was first reported by Titus et al. [68], and SEGR of power MOSFETs was first reported by Fischer [69]. SEB is usually due to the effect of the ion track on a parasitic device that is inherent in the device design. SEGR in power devices is related to a transient increase in the electric field across the gate dielectric again driven by the charge generated by the ion track.
Synthesis and modification of ZnO thin films by energetic ion beams
Published in Radiation Effects and Defects in Solids, 2021
Richa Krishna, Dinesh Chandra Agarwal, Devesh Kumar Avasthi
When the ion energy is around or higher than 1 MeV/nucleon, its velocity is of the order of Bohr electron velocity or higher. Such high velocity ions are referred to as swift heavy ions (SHI) and they pass through the matter very swiftly, either ionizing or exciting the atoms. In this way, the ion leaves behind a trail of excited atoms along its path. The temperature of this region increases tremendously termed as the thermal spike leading to a transiently molten track which, on ultra-fast quenching rate of 1014 K/s, results in a narrow cylindrical defected zone, known as columnar defect or ion track. Especially for insulator, the ion track formation occurs via Coulombic repulsion of positive ions surrounding ion path and is known as Coulomb explosion. The formation of ion track or latent track occurs in all the insulators and most of the semiconductors by SHI, whereas the metals (except Fe, Ti, Bi etc.) are not affected by SHI and the latent track formation does not occur in these. The value of Se where the formation of ion track starts to begin is called threshold Se and its value varies from material to material. Although the formation of ion track does not occur in all the materials by swift heavy ions, defect creation or defect annealing can occur. In some carbon nanostructures it is shown that each incident ion produces defects in the central core of ion path and annealing of defects occurs in the halo region surrounding the ion track region (24–28).
Ion Track Etching Revisited: IV. Thermal annealing of fresh swift heavy ion-irradiated PET in different environments
Published in Radiation Effects and Defects in Solids, 2021
J. Vacik, V. Hnatowicz, A. Kiv, D. Fink
Swift heavy ion (SHI) beams impinging into polymers are known to produce parallel linear trails of radiation damage, the so-called ‘latent ion tracks’ (22). These damaged zones are regions rich in excess free volume and in radiochemical products. The latter can be easily removed by aggressive chemicals such as alkaline (e.g. in the case of PET (5)), thus leaving straight nanopores with high aspect ratios in the solid. The diameter of these ‘etched ion tracks’ can be enlarged by prolonged etching. Etching of fresh SHI tracks as a function of the etching temperature has been examined many times for at least half a century (see, e.g. (23)); apart from highest etchant concentrations, it always follows Arrhenius correlations. The slope of these correlations differs somewhat for the etching of pristine and SHI-irradiated polymers, due to slightly different activation energies.
Phase transformation by the irradiation with swift heavy ions on vanadium oxide thin films
Published in Radiation Effects and Defects in Solids, 2020
Kapil Gupta, Sarvesh Kumar, Rahul Singhal
When an energetic ion interacts with a solid material then it loses its energy by the two main process (i) electronic excitation and (ii) elastic collisions. In case of swift heavy ions (SHIs) electronic excitation dominates over the elastic collisions. Lesueur (4) was the first to observe the amorphization of Pd80Si20 induced by the SHIs. Later on many researchers performed experiments in the electronic regime. It was reported by the experimental results that electronic excitation can induce structural modification, ion beam mixing, nano structuring and epitaxial crystallization (5). The energy transfer between the incident ion and the target material is based on the two mechanisms, thermal spike and ionic spike model. In ionic spike, incident ions create positively charged core along the path in the insulating materials. Mutual repulsion between positive ions causes them to explode out of the track until the positive ions are neutralized by free electrons. This explosion leads to a permanent damage of the lattice and forms an ion track. Thermal spike model, energy from incident ions is transferred to the atoms of the target material by two steps. Transfer of ion energy to the electrons of the material and then the distribution of this energy to the lattice via electron-phonon and phonon-phonon coupling (6). Passages of SHIs in the materials create cylindrical paths with the diameter of nanometers and increase the temperature along the ions path. Temperature of these narrow cylinders was rapidly increase and then quickly quenched by thermal conduction, results in modifying in the ion track path. Kokabi and colleagues (7,8) studied the effect of temperature-dependent 208Pb: 6.032 GeV heavy ions irradiation on the chromium doped vanadium sesquioxide (V1−xCx)2O3. It was reported that low temperature transition temperature of the system was dramatically shifted; also the resistivity in the metallic phase was reduced. It was also observed that the change in low temperature (LT) was prominent in the semiconducting phase in comparison to the metallic phase. Hofsass et al. (9) observed the change in the conductivity of the vanadium dioxide thin films irradiated by 1 GeV 238U ions. The change in the conductivity was explained on the basis of stress generated by the damage region along the SHIs tracks.