Thermal Spike Research Articles

Dark-field imaging and fluorescence dual-mode detection of microRNA-21 in living cells by core-satellite plasmonic nanoprobes

The in situ precise quantification and simultaneous imaging of low abundance microRNAs (miRNAs) within living cells is critical for cancer diagnosis, yet it remains a significant challenge. Leveraging the excellent sensitivity and spatiotemporal resolution of dark-field microscopy (DFM) and fluorescence imaging, we have successfully devised a novel detection approach using dual-signal reporter probes (DSRPs). These probes allow for highly sensitive detection of miRNA-21 in living cells via toehold-mediated strand displacement cascades. The DSRPs were constructed by Au nanoparticles and Ag nanoclusters core-satellite nanostructures. After the recognition of miRNA-21, the strand displacement cascades were triggered, inducing the disassembly of the Au/Ag core-satellite nanostructure with apparent scattering intensity decrease and peak wavelength shifts. Additionally, the fluorescence of Ag clusters could be recovered and further enhanced when in close proximity to specific guanine-rich strands. The dual-signal response capability enables the accurate detection of miRNA-21 from 1 fM to 1 nM, with a limit of detection reached 0.75 fM. DFM and fluorescent imaging of living cells efficiently confirms the applicable detection of miRNA-21 in complex detection media. The biosensor based on DSRPs represents a promising nanoplatform for visual monitoring and imaging of biomolecules in living cells, even at the single particle level.

Microstructural changes in GaN and AlN under 950 MeV Au swift heavy ion irradiation

The radiation hardness of GaN-based devices is a critical metric for applications in extreme environments. This study investigates the structural changes in GaN and AlN induced by swift heavy ion (SHI) irradiation, characteristic of space radiation environments. A multilayered GaN/AlN structure is exposed to 950 MeV Au ions at fluences of 1×1012 and 8×1012 ions/cm2. Subsequent post-irradiation characterization, including transmission electron microscopy and energy-dispersive x-ray spectroscopy, reveal no apparent amorphization across the entire sample. Notably, significant nanometer-sized cavities are observed in both GaN and AlN. The cavities in GaN exhibit an increase in number density and diameter with increasing SHI irradiation, with the average diameter progressing from 1.80 to 2.10 nm. In contrast, cavities in AlN appear considerably smaller. Molecular dynamics simulations, coupled with the inelastic thermal spike model, reproduce the presence of cavities in GaN and no cavities in the AlN structure. This difference is attributed to the faster heat dissipation and stronger bonding in AlN. Considering the overlapping of ion impacts at high fluences, simulations confirm the enlargement of cavity size in GaN. These findings contribute to a mechanistic understanding of the contrast in ion–matter interactions and induced microstructures between AlN and GaN under extreme ionizing radiation conditions. This disparity could potentially impact electronic performance through the formation of defect traps and interfacial strain fields.

The behavior of helium bubble evolution under neutron irradiation in different tungsten surfaces

Tungsten, as a kind of material for the plasma-facing wall in fusion reactor and tokamak, is subjected to irradiation by the high-energy neutron and the high fluxes of hydrogen and helium plasmas. Especially, in the presence of helium (He) bubbles, neutron irradiation can significantly exacerbate the deterioration of the material's mechanical properties. However, due to experimental limitations, the evolution of He bubbles in tungsten irradiated by neutrons and the underlying mechanisms remain unclear. Here, molecular dynamics (MD) simulation is used to investigate the behavior of He bubbles in tungsten with different crystal surfaces irradiated by neutrons. We observed the complete evolutionary process of the He bubble, i.e. standing, expanding, and bursting. During this process, high-energy neutron transfers energy to atoms within the He bubble through cascade collision, leading to a rapid increase in energy and pressure of the He bubble, and then the rapid expansion of the He bubble makes the pressure rapidly released, ultimately leading to the rupture of the helium bubble. Furthermore, we also explore the evolution of the He bubble under varying conditions (such as temperature, neutron energy, and He/vacancy ratio) within the same crystal surface. We found that at lower temperatures and neutron energy with a higher He/vacancy ratio, it tends to form pinhole-like channels to release helium atoms, resulting in the He bubble bursting. On the contrary, it tends to form a hill-like expansion to spurt helium atoms out, leading to the bubble bursting. Additionally, it was found that the direction and time of He bubble rupture varied under different crystal surfaces. He bubbles under the (112) surface burst the slowest with excellent corrosion resistance. These findings provide new insights into the behavior of irradiation resistance of fusion reactor materials under extreme conditions and offer significant guidance for the improvement and selection of optimal materials for plasma-facing walls.

Impact of discontinuous grain size distributions on the spectral energy distribution of debris disks

Context. The collisional evolution of debris disks is expected to cause the characteristic wavy pattern, that is, an under- or overabundance of particles of specific sizes, of grain size distributions. This perturbed grain size distribution potentially leaves characteristic patterns in the spectral energy distribution (SED) of the disk system. Aims. We aim to quantify and understand the specific influence of discontinuous particle size distributions on the appearance of debris disks. For this purpose, we considered dust emission models based on two different grain size distributions, namely, one with a single power law and one with a broken power law. In particular, our study is focused on the impact of an overabundance of small grains and an underabundance of medium-sized grains on the far-IR and (sub-)millimeter regime on the dust reemission radiation and the potential to constrain discontinuities in the grain size distribution from (sub-)millimeter photometric measurements of debris disks. Methods. We compared the spectral index α (Fν ∝ να) in the case of a continuous grain size distribution with that of a discontinuous grain size distribution. We performed this comparison for central stars with different spectral types and two different disk structures (e.g., slim and broad debris dust rings). Results. Within the considered parameter space, we found a characteristic difference between the spectral slopes of the SED in the different scenarios. In particular, the overabundance of small grains resulting from collisional events and thus parameters defining the outcome of disk events in debris disks is potentially observable by comparison with the SED corresponding to a grain size distribution resulting from an ideal collisional cascade. More specifically, the overabundance of small grains leads to a steeper slope in the far-IR and sub-millimeter regime, while the spectral index in the millimeter regime is hardly affected. On the other hand, the underabundance of medium-sized grains results in a slight steepening of the far-IR slope of the SED, but its primary effect is on the millimeter slope of the SED, causing it to become shallower. We also found that the impact of an overabundance of small dust particles is more pronounced than that of an underabundance of medium-sized dust particles. We also found that the difference between the spectral indices for the two different grain size distributions is largest for debris disks around brighter central stars and broader disks. However, the impact of the considered spatial distributions described by the fractional width of the disk system is weak. Our results also show that the dust composition is not the sole physical mechanism responsible for the spectral inversion observed in the far-IR to millimeter part of the SED of debris disk systems. Furthermore, the location of the spectral break is placed at different wavelength regimes if the grain size distribution is considered as a function of blowout size and stellar type.

Uncovering origin of grain boundary resistance to irradiation damage in NiCoCr multi-principal element alloys

Multi-principal element alloys (MPEAs) demonstrate significant promise as structural materials for nuclear energy equipment owing to their exceptional mechanical properties and radiation-resistant performances. In these alloys, the grain boundary (GB) serves as a crucial microstructure that typically mitigates irradiation damage by absorbing the irradiation-induced defect. However, the micromechanisms governing the anti-irradiation performance of GBs in MPEAs remain unclear. In this study, we investigate the irradiation defect production during collision cascade in the model NiCoCr bicrystal system through atomic simulations, aiming to unveil the atomic-scale origin of GB to resist irradiation damage in MPEAs. The results reveal that GBs effectively serve as sinks for irradiation defects in NiCoCr. The sink efficiency depends on the GB energetic state, including GB excess energy and defect segregation energy, as well as the energetic difference between interstitial and vacancy segregation. Statistical analysis identifies a universally exponent function between the defect absorption rate at GB and GB energetic state. In NiCoCr, the GB-disorder-induced-entropy increase leads to a biased reduction in interstitial segregation energy, narrowing the gap between interstitial and vacancy segregation energies by approximately 11 % compared to Ni. This improvement enhances the overall resistance of GBs to irradiation damage. Additionally, preferential segregation of Ni interstitial atoms is notably enhanced in NiCoCr, contributing to a high defect absorption rate at GBs. This study provides new insights into the resistance of GBs to irradiation defects in MPEAs and suggests GB engineering as an effective strategy for developing advanced alloys with enhanced radiation tolerance.

Latent ion tracks were finally observed in diamond

Injecting high-energy heavy ions in the electronic stopping regime into solids can create cylindrical damage zones called latent ion tracks. Although these tracks form in many materials, none have ever been observed in diamond, even when irradiated with high-energy GeV uranium ions. Here we report the first observation of ion track formation in diamond irradiated with 2–9 MeV C60 fullerene ions. Depending on the ion energy, the mean track length (diameter) changed from 17 (3.2) nm to 52 (7.1) nm. High resolution scanning transmission electron microscopy (HR-STEM) indicated the amorphization in the tracks, in which π-bonding signal from graphite was detected by the electron energy loss spectroscopy (EELS). Since the melting transition is not induced in diamond at atmospheric pressure, conventional inelastic thermal spike calculations cannot be applied. Two-temperature molecular dynamics simulations succeeded in the reproduction of both the track formation under MeV C60 irradiations and the no-track formation under GeV monoatomic ion irradiations.

Defects Act in an “Introverted” Manner in FeNiCrCoCu High-Entropy Alloy under Primary Damage

High-entropy alloys (HEAs) attract much attention as possible radiation-resistant materials due to their several unique properties. In this work, the generation and evolution of the radiation damage response of an FeNiCrCoCu HEA and bulk Ni in the early stages were explored using molecular dynamics (MD). The design, concerned with investigating the irradiation tolerance of the FeNiCrCoCu HEA, encompassed the following: (1) The FeNiCrCoCu HEA structure was obtained through a hybrid method that combined Monte Carlo (MC) and MD vs. the random distribution of atoms. (2) Displacement cascades caused by different primary knock-on atom (PKA) energy levels (500 to 5000 eV) of the FeNiCrCoCu HEA vs. bulk Ni were simulated. There was almost no element segregation in bulk FeNiCrCoCu obtained with the MD/MC method by analyzing the Warren–Cowley short-range order (SRO) parameters. In this case, the atom distribution was similar to the random structure that was selected as a substrate to conduct the damage cascade process. A mass of defects (interstitials and vacancies) was generated primarily by PKA departure. The number of adatoms grew, which slightly roughened the surface, and the defects were distributed deeper as the PKA energy increased for both pure Ni and the FeNiCrCoCu HEA. At the time of thermal spike, one fascinating phenomenon occurred where the number of Frenkel pairs for HEA was more than that for pure Ni. However, we obtained the opposite result, that fewer Frenkel pairs survived in the HEA than in pure Ni in the final state of the damage cascade. The number and size of defect clusters grew with increasing PKA energy levels for both materials. Defects were suppressed in the HEA; that is to say, defects were “cowards”, behaving in an introverted manner according to the anthropomorphic rhetorical method.

Exploring multi-decadal time series of temperature extremes in Australian coastal waters

Abstract. The intensity and frequency of extreme ocean temperature events, such as marine heatwaves (MHWs) and marine cold spells (MCSs), are expected to change as our oceans warm. Little is known about marine extremes in Australian coastal waters, particularly below the surface. Here we introduce a multi-decadal observational record of extreme ocean temperature events starting in the 1940s and 1950s between the surface and the bottom (50–100 m) at four long-term coastal sites around Australia: the Australian Multi-Decadal Ocean Time Series EXTreme (AMDOT-EXT) data products (https://doi.org/10.26198/wbc7-8h24, Hemming et al., 2024). The data products include indices indicating the timing of extreme warm and cold temperature events, their intensity and the corresponding temperature time series and climatology thresholds. We include MHWs, MCSs and shorter-duration heat spikes and cold spikes. For MHWs and MCSs, which are defined as anomalies above the daily varying 90th and 10th percentiles, respectively, and lasting more than 5 d, we also provide further event information, such as their category and onset and decline rates. The four data products are provided as CF-compliant NetCDF files, and it is our intention that they be updated periodically. It is advised that data users seek the latest data product version. Using these multi-decadal data products, we show the most intense and longest extreme temperature events at these sites, which have occurred below the surface. These data records highlight the value of long-term full water column ocean data for the identification of extreme temperature events below the surface.

Resident space objects classification by machine learning techniques

In recent years the number of resident space objects in near-Earth space has been increasing drastically, which can lead to a “cascade collisions” effect and other catastrophic consequences. Therefore, it is crucial to monitor resident space objects, maintain and update catalogues on time, including the identification of unknown space objects to estimate their location and potential orbit. It is necessary to perform resident space object identification quickly and accurately to avoid possible satellite collisions resulting in large clouds of uncontrollable space debris fragments. That is why the task of resident space object preliminary classification by TLEs is stated and solved by applying machine learning approaches to achieve a higher classification quality and speed. This issue is a highly imbalanced classification problem, which narrows and specifies the used models. Applying the proposed resident space object classification model to space surveillance systems can decrease the time required for the object identification significantly.

Deflection of dangerous middle-size LEO debris with autonomous space-based laser brooms via surgical actions

There is a consensus that the increasingly large number of LEO debris objects represents a major threat to both active and defunct satellites and that means a potential runaway collisional cascading. This problem urgently demands to be addressed immediately, since the number of satellites in LEO is also dramatically increasing.Many active space debris removal programs have been proposed and those based on using laser from space appear to be really promising, taking into account that one of the most challenging issues from the orbital standpoint is to guarantee the appropriate accuracy for the laser beams that are shot from space-based LEO trackers.In this work, we propose how to build up space-based laser brooms consisting of a significant number of autonomous LEO trackers aimed at performing surgical local shooting actions to deflect the most dangerous middle-size debris objects into the Atmosphere by means of laser ablation.The precision of these brooms lies in the use of the post-Newtonian equations for the computation of absolute and relative positions and velocities, as well as ranges.

Magnetic power spectrum variability with large-scale total magnetic field fluctuations

The Parker Solar Probe (PSP) is operational since 2018 and has provided invaluable new data that measure the solar vicinity in situ at smaller heliocentric distances than ever before. These data can be used to shed new light on the turbulent dynamics in the solar atmosphere and solar wind, which in turn are thought to be important to explain long-standing problems of the heating and acceleration in these regions. In recent years, it was realized that background inhomogeneities in magnetohydrodynamics could influence the development of turbulence and might enable other cascade channels, such as the self-cascade of waves, in addition to the well-known Alfvén collisional cascade. This phenomenon has been called uniturbulence. However, the precise influence of the background inhomogeneity on turbulent spectra has not been not studied so far. In this work, we study the influence of background roughness on the turbulent magnetic field spectrum in PSP data, including data from encounter 1 up to and including encounter 14. The magnetic spectral index $ receives our highest attention. Motivated by the presumably different turbulent dynamics in the presence of large-scale inhomogeneities, we searched for correlations between the magnetic power spectra and a measure for the degree of inhomogeneity. The latter was probed by taking the standard deviation (STD) of the total magnetic field magnitude after applying an appropriate averaging. The data of each PSP encounter were split into many short time windows, of which we subsequently calculated both $ and background STD. We find a significant impact of the background STD on $ As the variations in the background become stronger, $ becomes more negative, indicating a steepening of the magnetic power spectrum. We show that this effect is consistent in all investigated PSP encounters, and it is unaffected by heliocentric distance up to $50 R_ By making use of artificial magnetic field data in the form of synthetic colored noise, we show that this effect is not simply due to the fluctuations imposed on the total magnetic field, but must have another as yet unidentified cause. There is a strong indication that the background inhomogeneity affects the turbulent dynamics, possibly through uniturbulence. This leads to a different power spectrum in the presence of large-scale total magnetic field variations. The fact that it is present in all investigated encounters and at all radial distances up to $50 R_ suggests that it represents a general and ubiquitous feature of solar wind dynamics. The analysis with the synthetic colored noise indicates that the observed steepening effect is not to be attributed simply to the small-scale fluctuations superposed on the total magnetic field. This conclusion is confirmed by the fact that no similar consistent steepening trend is observed for the magnetic compressibility $C_b$ instead of background STD. The steepening trend is instead a real physical effect induced by the large-scale variations in the background magnetic field.

Ion Tracks and Nanohillocks Created in Natural Zirconia Irradiated with Swift Heavy Ions.

Natural monoclinic zirconia (baddeleyite) was irradiated with 340 MeV Au ions, and the irradiation-induced nanostructures (i.e., ion tracks and nanohillocks) were observed using transmission electron microscopy. The diameter of the nanohillocks was approximately 10 nm, which was similar to the maximum molten region size calculated using the analytical thermal spike model. Ion tracks were imaged as strained regions that maintained their crystalline structure. The cross-sections of most of the ion tracks were imaged as rectangular contrasts as large as 10 nm. These results strongly indicated that the molten region was recrystallized anisotropically, reflecting the lattice structure. Furthermore, low-density track cores were formed in the center of the ion tracks. The formation of low-density track cores can be attributed to the ejection of molten matter toward the surface. A comparison of the ion tracks in the synthetic zirconia nanoparticles and those in larger natural zirconia samples showed that the interface between the strained track contrast and the matrix was less clear in the former than in the latter. These findings suggest that the recrystallization process was affected by the size of the irradiated samples.

Molecular dynamics simulations of displacement cascades in LiAlO2 and LiAl5O8 ceramics

Molecular dynamics was employed to investigate the radiation damage due to collision cascades in LiAlO2 and LiAl5O8, the latter being a secondary phase formed in the former during irradiation. Atomic displacement cascades were simulated by initiating primary knock-on atoms (PKA) with energy values = 5, 10 and 15 keV and the damage was quantified by the number of Frenkel pairs formed for each species: Li, Al and O. The primary challenges of modeling an ionic system with and without a core–shell model for oxygen atoms were addressed and new findings on the radiation resistance of these ceramics are presented. The working of a variable timestep function and the kinetics in the background of the simulations have been elaborated to highlight the novelty of the simulation approach. More importantly, the key results indicated that LiAlO2 experiences much more radiation damage than LiAl5O8, where the number of Li Frenkel pairs in LiAlO2 was 3–5 times higher than in LiAl5O8 while the number of Frenkel pairs for Al and O in LiAlO2 are ~ 2 times higher than in LiAl5O8. The primary reason is high displacement threshold energies (Ed) in LiAl5O8 for Li cations. The greater Ed for Li imparts higher resistance to damage during the collision cascade and thus inhibits amorphization in LiAl5O8. The presented results suggest that LiAl5O8 is likely to maintain structural integrity better than LiAlO2 in the irradiation conditions studied in this work.

Atomic-level insight into process and mechanism of ion beam machining on aluminum optical surface

Polycrystalline Al workpieces go through a complex surface atom sputtering and surface/subsurface atom diffusion throughout the ion beam machining process that plays a critical role in determining machining quality of optical mirror surfaces. Here, we leverage molecular dynamics method for the first time to reveal the machining mechanism and the polycrystalline effect of aluminum during ion beam sputtering, in term of cascade collision, atom trajectory, sputtering yield, and surface characteristic. Polycrystalline Al presents a significant low potential energy state, leading to milder cascade collision and weaker sputtering effects than monocrystalline Al during ion beam machining. The atom trajectory demonstrates irregular variation as the atom diffusion is blocked by grain boundary (GB) in polycrystalline Al, leading to the relief microstructure and poor surface quality. With incident ions increasing, the GBs are broken and atom diffusion enhancing, as well as lower subsurface defects and better finishing surface quality. The microscopic morphology evolves into gravel microstructure. Simulation results also reveal that atom diffusion will benefit from high ion concentration and low ion energy. Sputtering yield variation is more sensitive to ion energy. To acquiring better finishing surface quality of Al without influencing machining efficiency, ion concentration must be increased while the ion energy needs to be decreased appropriately but a large number of cascading collisions need to be ensured.

Helium bubble evolution under cascade in bcc iron relevant to fusion conditions investigated by a novel coupling MD-OKMC method

The direct interaction between cascade and helium bubbles during the thermal spike phase plays an important role in the helium bubbles evolution in metals, which was not fully considered by the present long-time simulation methods. To address this issue, in this work we developed a coupling MD-OKMC method to investigate the helium bubble evolution under irradiation cascade in bcc iron. The short-time collision cascade was simulated by the molecular dynamics (MD), and the long-time helium bubble evolution was modeled by the object kinetic Monte Carlo (OKMC). The MD and OKMC simulations were alternated to imitate the gradual increase of both irradiation dose and helium concentration under experiment conditions. The impact of temperature on the helium bubble evolution under irradiation cascade in bcc iron was investigated and the results were compared with the data from neutron irradiation experiment. It's found that the results of the coupling MD-OKMC were consistent with the experiment results, and were better in agreement with the experiment than the traditional OKMC.

The sink efficiency of symmetric tilt grain boundary under displacement cascade in zirconium

Molecular dynamic (MD) simulation was performed to investigate the sink efficiency of [12¯10]symmetric tilt grain boundaries (STGBs) to irradiation point defects in zirconium (Zr). A total of 15 STGBs with the rotation angle ranged from 0 to 90° were studied during displacement cascade. The results show that the sink efficiency to point defects (especially interstitials) of GB is stronger than that of twin boundary (TB), since the atoms at grain boundary dislocations (GBDs) are loosely arranged with high atomic volume to form channels to absorb interstitials. The higher GB energy indicates the lower coherency of GB including more complex GBD structure, thus the GB has a stronger absorption ability to interstitials. The GB migration induced by displacement cascade is mainly attributed to the cavity formed by the remaining vacancies as the interstitials are absorbed and trapped by GBDs. This work provides new insights of relationship between GB sink efficiency and GB characters, which are important for understanding the irradiation effects in Zr alloys.

Self-interstitial atom properties in Nb–Mo–Ta–W alloys

Self-interstitial atoms (SIA) are generated in collision cascades during high-energy particle irradiation of crystalline materials. In pure metals, SIA generally adopt split configurations and display fast mobilities along one-dimensional trajectories. This differentiates them from vacancies, which move in confined three-dimensional paths. This asymmetry is one of the pillars of irradiation damage theories that have been successful in explaining a number features of the irradiation response of pure metals and dilute alloys. However, in complex concentrated alloys consisting of several metallic elements in equal or near equal proportions, lattice distortions associated with compositional fluctuations change the potential energy landscape on atomic scales, leading to SIA structures not seen in their pure metal counterparts. In this paper, we use atomistic simulations to study the properties of self-interstitial atoms in the quaternary equiatomic Nb–Mo–Ta–W refractory alloy. Chemically, these SIA defects adopt a variety of structures involving all pairs of atoms. We find the 〈111〉 orientation to be the most common among all split configurations, but we also observe – surprisingly – a relatively high occurrence of octahedral SIA. In terms of their diffusivities, we find two clearly distinguished regimes below and above 600 K, where the SIA diffusion changes dimensionality from 1D to 3D. We calculate the migration energies and diffusion pre-factors in both regions, from which we extract the translational and rotational components of the defect migration. We find values of 0.25 eV and pre-factors of ∼10−11 m2 s−1 in the low temperature regime, and 0.57 eV and ∼10−8 m2 s−1 in the high temperature one. From this, we estimate a rotational energy barrier of 0.37 eV.

Enhancing damping-like efficiency by low-energy mixed ions bombardment

Pursuing enhanced spin–orbit torque (SOT) has become a significant focus for achieving energy-efficient spintronics devices. Researchers have explored different materials, layer engineering, and various post-deposition modification methods to realize higher SOT. Here, we have utilized the bombardment of mixed ions (Ar+ and He+ in various ratios) with 0.6 kV bias voltage to enhance the SOT efficiency in a Pt/Co/W stack. The bombardment modifies the physical properties (magnetic, electric, and structural) due to cascade collision, knocking off atoms (from the surface), and ion implantation. The increased percentage of He+ suppresses the drastic behavior of cascade collisions, and hence, the properties are tunable by changing the gas ratio. We exploited this behavior to design a material stack with enhanced SOT efficiency. We fabricated Hall bars to quantify SOT and observed a 4.5× increase in the effective damping-like efficiency. The efficiency and switching current density in the stack could be tuned by the variation of Ar:He ion ratio and the exposure duration. This study offers an easy route to tune the energy efficiency of spin devices, contributing to the advancement of next-generation spintronics.

Molecular Dynamics Simulations of Displacement Cascade in Ni-Based Concentrated Solid Solution Alloys

Molecular Dynamics Simulations of Displacement Cascade in Ni-Based Concentrated Solid Solution Alloys

Tunable formation of gold nanoparticles on polymer by keV ion beam irradiation

The formation of nanostructures from a thin Au film deposited on a polystyrene and polymethylmethacrylate substrate under keV monatomic P, Ta and molecular PF4 ion irradiation is studied. The formation of nanoparticles on both kinds of polymers is shown. Heavy Ta ions are most effective in altering the Au layer, whereas its transformation by light P or molecular PF4 ions is less pronounced. Irradiation with PF4 ions has a much smaller effect on the PS and PMMA substrate bulk compared to that with monatomic P ions. The crucial role of collision cascade density in the process of thin metallic film coagulation on polymer substrate is revealed. During ion bombardment, transmitted IR light intensity increases proportionally to the area covered by the metal film, which makes it possible to use FTIR as a rapid technique to estimate the state of the nanoparticle formation process.