Ion-Surface Interaction Mechanisms #AcademicAchievements

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Swift heavy ions (SHI) are ions with very high kinetic energy (often of the order of MeV per nucleon or greater), and when they impinge on materials such as silicon nanostructures (nanocubes, nanowires, thin films) or silicon surfaces, the energy deposition process is complex, involving electronic excitations, electron emission, and a competition among energy retention vs loss to surroundings. The recent study titled “Energy Deposition upon Swift Heavy Ion Impact in Silicon Nanostructures and Surfaces” (Ε½ugec & KarluΕ‘iΔ‡, Materials, 2025) explores how much of the deposited energy remains within the nanoscale target, and how much is lost, especially via escaping electrons. The findings have implications for radiation hardness, nanostructure modification, surface patterning, and modelling of ion track formation. MDPI

In this work, Geant4 simulations (with the MicroElectronics package) were used to model the passage of swift heavy ions through silicon structures of sizes between ~5 nm to 100 nm, in several geometries: nanocubes, nanowires, thin films, and also at surfaces (especially for grazing incidence). The ions studied cover a range of kinetic energies (for silicon ions) from ~2.8 MeV up to 280 MeV. The goal: to quantify the energy deposition, energy retained within the target, and how much energy is carried away by electrons—primary and secondary. Especially in nanoscale structures, where dimensions can be comparable to the mean free path of high‐energy electrons, a significant fraction of energy can escape, reducing the energy available for heating, phase change, or damage. MDPI

One of the main findings is that for small nanostructures, especially at lower sizes (e.g. 5-30 nm), a large fraction of deposited energy is lost via emission of electrons. For instance, in a 30 nm silicon nanocube impacted by a 28 MeV Si ion, a portion of the energy is retained, but a noticeable fraction is carried away by primary electrons escaping from the structure. The radial and longitudinal profiles of energy density show that the deposited energy near the path of the ion is high, but energy retention is reduced when electrons escape. MDPI

As the SHI energy increases, the trend is that percentage of retained energy decreases (except sometimes at the lowest energies). Larger nanocubes or thicker films or larger structures tend to retain more energy simply due to geometry: there’s more material to absorb electrons and less surface area relative to volume for electrons to escape. But even in larger nanostructures (e.g. 100 nm size), at high SHI energies, a non-trivial fraction of the deposited energy is lost. So geometrical size and energy both matter. MDPI

The study also investigates nanowires and thin films. Nanowires (length ~100 nm, variable cross section) show somewhat similar behavior to nanocubes: those electrons generated near or along the path of the SHI have some chance to escape, especially from sides or ends. Thin films also show escaping electrons, particularly from surfaces and lateral edges, which reduces energy retention. The lateral (side) emission becomes more significant for thin films because of their geometry: large lateral surfaces mean high chance for electrons produced near those surfaces to escape. MDPI

Surface effects are particularly interesting. When SHI hits at grazing incidence (i.e., at shallow angles near the surface), the energy deposition near the surface is altered because electrons have shorter paths before they might escape, and the geometry is such that part of the ion track is essentially near or exposed at the surface. The study finds that for grazing incidence, the first few nanometers (≈3 nm) below the Si surface are especially significant: retention of energy is reduced in this layer (over ~50% energy can be lost under certain conditions) when the incident SHI energy is large. This implies that modelling of surface tracks or modifications must correctly account for electron emission and surface leakage of energy. MDPI

The implications are important: in modelling damage thresholds, track formation, nanoscale modifications, and in designing radiation hard nanoscale silicon devices, the fact that energy deposition is not fully retained must be included. Traditional thermal spike models or molecular dynamics ones often assume that energy deposited (especially electronic energy loss) remains locally and is converted into heat or structural change; but if significant amounts are lost via electron escape (especially in nanoscale structures), those assumptions may overestimate damage or modification. So for nanomaterials, the effective energy available for modification is less than the deposited energy. MDPI

Now, connecting this to wider recognition and academic dissemination: this work, which fills a gap in understanding energy dissipation in nanoscale silicon under SHI impact, is of high significance in materials physics, nanotechnology, and radiation effects. If this or similar work is part of your research or you want to highlight it, platforms for recognition are relevant. You could consider nominations through Academic Achievements, which showcases impactful work. Also, there's the Academic Achievements Award Nomination route to nominate your research for awards. Using those links can bring more visibility and support to advancing understanding in SHI energy deposition, engineering applications, and fundamental science.

Further details: the simulations used work function of silicon (~4.8 eV) to determine whether electrons reaching the surface have enough energy to overcome that barrier; electrons with energies less than that are assumed to deposit their energy locally. Also, low-energy electrons (<16.7 eV) have specific handling: unless their final step is very near the surface (~1 nm) they are treated as depositing energy locally in the simulation. These practical details make the retention vs emission predictions more realistic. MDPI

Another key result: angle of incidence matters. For normal incidence, electron emission and energy loss still occur, but grazing incidence enhances surface leakage effects. Also, for surfaces, the depth below the surface where SHI passes affects retention: shallow passage means more energy is lost to the vacuum side. The simulations show that up to about 3 nm below the surface, the effect is large; past that depth, retention improves somewhat, but never reaches perfect retention since some escape paths remain. MDPI

Also, the number of emitted electrons, their energy spectra, and directional (angular) dependence are characterized. Primary electrons (those directly knocked out by the ion) carry most of the escaping energy; secondary electrons (from cascades) tend to have lower energies, more likely to be stopped or reabsorbed. The study shows that the energy carried away by primary electrons is the dominant pathway for the energy loss. Angular distributions show more emission forward (in direction of ion exit) than sideways or backward. MDPI

In summary, the study demonstrates that in silicon nanostructures and surfaces subjected to swift heavy ion impact: (1) energy retention is lower than deposited energy because of electron emission; (2) size, shape, thickness, and geometry (cube, wire, film) play a strong role; (3) incident energy of the ion also strongly influences retention (higher energy → more emission losses); (4) surface effects (especially grazing incidence and depth below surface) significantly reduce energy retention in near-surface layers; and (5) modelling of ion track formation and damage must integrate these loss pathways to avoid overestimation of modification or damage. MDPI

Given these findings, there are several suggestions for future work: experimental validation of the simulation results (measurement of electron emission, measurement of damage thresholds in very small nanostructures), extending to other materials (e.g. different semiconductors, 2D materials), exploring the effect of ion charge state, exploring how dopants or surface passivation may limit or enhance electron escape, and applying molecular dynamics coupled with thermal spike models that explicitly include electron emission losses.

Now, bringing back to visibility, recognition, and academic merit: because this area is advancing with important implications for nanotechnology, semiconductors, and radiation hard electronics, recognizing this kind of work is valuable. You (or your group) might want to submit or nominate this research for awards or fellowships via Academic Achievements. Or use the Academic Achievements Award Nomination to highlight the novelty of accounting for energy loss via electrons in nanostructures. Prominent recognition helps in garnering support, funding, collaboration, and raising awareness of nuanced effects in SHI–nanomaterial interactions.

Using those platforms (i.e. Academic Achievements and Academic Achievements Award Nomination) allows you to showcase work like this, linking simulations, nano-scale geometries, and experimental potential. Don’t overlook the importance of special issues, conferences, and awards that encourage precise modelling or that reward breakthroughs in understanding nanoscale energy deposition.

To conclude, “Energy Deposition upon Swift Heavy Ion Impact in Silicon Nanostructures and Surfaces” reveals essential truths: that in nanoscale systems, a large portion of excitation energy may escape rather than contribute to local heating or damage, that geometry, size, energy, incidence angle and surface depth all modulate how much energy is retained, and that these factors must be incorporated into predictive models for materials under ion irradiation. Recognizing and nominating such research through channels like Academic Achievements and Academic Achievements Award Nomination can help foster further development, awareness, and application in this critical field. #SwiftHeavyIon #Nanostructures #SiliconPhysics #RadiationHardness #IonTrackFormation #ElectronEmission #SurfaceEffects #EnergyRetention #MaterialsScience #AcademicAchievements

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