Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Temperature of thermal spikes induced by swift heavy ions
Introduction
Recently we have observed desorption of gold nanoparticles from surfaces of amorphous silicon nitride (a-SiN) and amorphous silicon oxide (a-SiO2) upon impact of 420 MeV Au ions [1]. The gold nanoparticles were desorbed as liquid droplet without fragmentation and the desorption occurs in the vicinity (∼several nm) of the ion impact position. The mechanism of the observed desorption was ascribed to a so-called popcorn mechanism [2]. When nanoparticles are heated beyond their melting point in a short time period a sudden volume expansion occurs upon melting of nanoparticles. As a result, a large compressive pressure will build up in the nanoparticle. If this pressure is high at the substrate–nanoparticle interface, it will accelerate the nanoparticle away from the surface, leading to desorption. Actually, molecular dynamics (MD) simulations showed that gold nanoparticles are desorbed as liquid droplets from a surface when they are energized beyond 0.4 eV/atom [3]. This threshold energy (0.4 eV/atom) is close to, but slightly smaller than, the energy to reach the melting temperature of gold (1338 K = 0.346 eV/atom) plus the latent heat (0.132 eV/atom) of melting. This was attributed to the size effect on the melting temperature. Thus, the observed nanoparticle-cleared region corresponds to the region where the temperature surpassed 0.4 eV/atom during the evolution of the thermal spike. This allows us to trace the temperature of thermal spikes. The feasibility of this new temperature tracing method was already examined by comparing the observed radius of the gold-nanoparticle-cleared region with the theoretical calculation using the inelastic thermal spike (i-TS) model [1]. In the present work, we extend our previous work. We measure detailed temperature distributions of thermal spikes using nanoparticles of different materials which have different melting temperatures. We observe desorption of gold, platinum and palladium nanoparticles upon irradiation of 100 MeV Xe and 420 MeV Au ions on a-SiN films. The derived temperature distributions are compared with the results of the i-TS calculations.
Section snippets
Experimental
Self-supporting a-SiN films of 30 nm thickness (nominal density 3 g/cm3) prepared by chemical vapor deposition were purchased from Silson Ltd. The composition of the a-SiN film was determined to be Si0.47 ± 0.02N0.53 ± 0.02 using high-resolution Rutherford backscattering spectrometry [4]. Gold, platinum or palladium nanoparticles were deposited on each a-SiN film by vacuum evaporation. The prepared nanoparticle-deposited films were irradiated with 100 MeV Xe and 420 MeV Au ions at normal incidence to a
Results and discussion
Fig. 1(a) shows an example of the TEM bright field images of the Pt-deposited a-SiN film observed before irradiation. There are many platinum nanoparticles formed by the vapor deposition. The areal density, N, of these nanoparticles was measured to be 9.5 × 1012 particles/cm2. The size distribution of these nanoparticles was derived from the observed TEM images. The distribution shows a Gaussian-like well-defined peak with a peak diameter of 1.5 nm and FWHM of 0.95 nm. Similar size distributions were
Conclusion
The temperature distributions of thermal spikes in a-SiN films produced by 420 MeV Au and 100 MeV Xe ions were evaluated by observing desorption of Pt, Pd and Au nanoparticles. The temperature at the entrance surface was found to be lower than the temperature at the exit surface for both ions. This is attributed to the effect of δ-rays emitted by the projectile ions. The observed temperature distributions are well reproduced by the i-TS calculations for 420 MeV Au ions. For 100 MeV Xe ions,
Acknowledgement
This work was performed under the shared use program of JAEA facilities. The authors are grateful to the technical staff of the accelerator facilities at JAEA/Tokai for the swift heavy ion irradiation. This work was partly supported by JSPS KAKENHI Grant (Grant Number 26246025).
References (8)
- et al.
Nucl. Instrum. Methods Phys. Res. Sect. B
(2011) - et al.
Nucl. Instrum. Methods Phys. Res. Sect. B
(2009) - et al.
Nucl. Instrum. Methods Phys. Res. Sect. B
(2014) - et al.
Mater. Fys. Med.
(2006)
Cited by (6)
Study on structural properties of swift heavy ion induced damage in Al<inf>2</inf>O<inf>3</inf>
2023, Radiation Physics and ChemistryAnalysis of the microstructural evolution of silicon nitride irradiated with swift Xe ions
2020, Ceramics InternationalCitation Excerpt :Latent track formation in silicon nitride doped with Al has been observed after irradiation with 220 MeV Xe ions at the temperatures 80, 300 tо 1000 K not including any detail on track sizes or morphology [2,3]. Data on track parameters in thin films (5–100 nm) of amorphous silicon nitride (a-Si3N4) irradiated with xenon ions (100 MeV), gold ions (200, 420 MeV) and fullerenes with energies in the low MeV range were analysed using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) [4–6]. In these papers it is suggested that the ion track region has a core-shell structure because the HAADF-STEM images show darker contrast due to reduced density in the track interior surrounded by a brighter shell.
Structure and crystal field analysis using ionoluminescence of Al<inf>2</inf>O<inf>3</inf>: Tm<sup>3+</sup> phosphor
2019, Journal of LuminescenceCitation Excerpt :The temperature induced by Si8+ ion along its trajectory in Al2O3: Tm3+ is estimated using the thermal spike model (TSM). The TSM can be expressed by two mathematically coupled equations governing the energy distribution on electronic and lattice subsystem [53–55]. The evolution of atomic temperature versus time at a different radial distance from the 100 MeV Si8+ ion trajectory in Al2O3: Tm3+ using TSM simulation codes is shown in Fig. 8.