Anisotropic Core-Shell Swift Heavy Ion Tracks in beta-Ga2O3
School of Nuclear Science and Technology, Xi’an Jiaotong University（西安交通大学核科学与技术学院）；Materials Science and Environmental Engineering Unit, Tampere University（坦佩雷大学材料科学与环境工程单元）；Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）；Department of Nuclear Physics, China Institute of Atomic Energy（中国原子能科学研究院核物理系）；Department of Physics and Helsinki Institute of Physics, University of Helsinki（赫尔辛基大学物理系与赫尔辛基物理研究所）；The Hong Kong Microelectronics Research and（香港微电子研究）
Swift heavy ion (SHI) irradiation generates nanoscale ion tracks through intense electronic excitation, yet the microscopic mechanisms governing their morphology and phase stability in low symmetry oxides remain poorly understood. Here, a multiscale atomistic simulation framework is used to investigate the formation and recovery of SHI-induced tracks in monoclinic $β$-Ga2O3 over a wide range of electronic energy losses (Se) and crystallographic orientations. A sequence of distinct structural responses is identified with increasing Se: (i) complete lattice recovery at low Se; (ii) recrystallization into a metastable $γ$-Ga2O3 phase at intermediate Se; and (iii) the formation of core-shell ion tracks at high Se, consisting of an amorphous core surrounded by a recrystallized $γ$-phase shell. Despite the essentially isotropic initial energy deposition, the final ion-track morphology exhibits pronounced crystallographic anisotropy, governed by orientation-dependent recovery dynamics. The superior recrystallization along the [010] direction is attributed to its exceptionally high elastic stiffness. Notably, SHI irradiation perpendicular to the (100) plane induces a more severe structural response at low Se ($\le$ 10 keV/nm), however, at higher Se, it yields a smaller residual ion track compared to the other orientations. The simulated ion-track sizes show excellent quantitative agreement with the available experimental measurements over a wide range of Se values. These findings establish a unified atomic-scale picture of core-shell track formation and anisotropic recovery in $β$-Ga2O3.
A systematic study of the $R_e$-$T_m$ relation ($R_e$ = track radius, $T_m$ = melting temperature) in insulators reveals new features of track formation. A quantitative relationship is demonstrated between $R_e$ values measured in various solids when $\langle s_e\rangle$=constant ($\langle s_e\rangle$ = atomic stopping power). This effect is the consequence of a composition-independent, identical maximum temperature distribution $ΔT(r,0)$, which is induced in various insulators in a narrow cylindrical volume close to the tracks. The uniformity ceases gradually at larger distances. $ΔT(r,0)$ ha…
Atomistic Mechanisms of Temperature-Dependent Ion Track Formation in Gallium Nitride under Swift Heavy Ion Irradiation
School of Nuclear Science and Technology, Xi’an Jiaotong University（西安交通大学核科学与技术学院）；Academy of Chips Technology, China Electronics Technology Group Corporation（中国电子科技集团公司芯片技术研究院）；National Key Laboratory of Integrated Circuits and Microsystems（集成电路与微系统国家重点实验室）
Track radii Re induced by swift heavy ions are studied. The experimental track data are analyzed in Gd2Ti2O7 pyrochlore in the range Se=6-54 keV/nm (Se - electronic stopping power) including irradiations by low and high velocity ions. The Analytical Thermal Spike Model (ATSM) is applied whose main features are reviewed. The track data of Gd2Ti2O7 exhibit scaling features which mean simple quantitative relationships with track sizes of other insulators controlled only by a single materials parameter (MP), the melting temperature Tm. The Re2-Se track evolution curve is described in the whole ran…
Ion track formation, amorphisation, and the formation of porosity in crystalline GaSb induced by 185 MeV $^{197}$Au swift heavy ion irradiation is investigated as a function of fluence and irradiation angle relative to the surface normal. RBS/C and SAXS reveal an ion track radius between 3 nm and 5 nm. The observed pore morphology and saturation swelling of GaSb films shows a strong irradiation angle dependence. Raman spectroscopy and scanning electron microscopy show that the ion tracks act as a source of strain in the material leading to macroscopic plastic flow at high fluences and off norm…
Creating mixed-phase states in cadmium sulfide by swift heavy ion irradiation
Institute of Physics, Czech Academy of Sciences（捷克科学院物理研究所）；Higher Institute of Technologies and Applied Sciences, University of Havana（哈瓦那大学高等技术与应用科学学院）；Institute of Plasma Physics, Czech Academy of Sciences（捷克科学院等离子体物理研究所）
Effect of radially heterogeneous band gap collapse on formation of swift heavy ion tracks in Al2O3
P.N. Lebedev Physical Institute of the Russian Academy of Sciences（俄罗斯科学院列别捷夫物理研究所）；Institute of Physics, Czech Academy of Sciences（捷克科学院物理研究所）；Institute of Plasma Physics, Czech Academy of Sciences（捷克科学院等离子体物理研究所）
Second comment on "Dense and nanometric electronic excitations induced by swift heavy ions in an ionic CaF2 crystal: Evidence for two thresholds of damage creation"
The electrical characteristics and microstructures of $β$-Ga$_2$O$_3$ Schottky barrier diode (SBD) devices irradiated with swift heavy ions (2096 MeV Ta ions) have been studied. It was found that $β$-Ga$_2$O$_3$ SBD devices showed the reliability degradation after irradiation, including turn-on voltage Von, on-resistance Ron, ideality factor n and the reverse leakage current density Jr. In addition, the carrier concentration of the drift layer was decreased significantly and the calculated carrier removal rates were 5*106 - 1.3*107 cm-1. Latent tracks induced by swift heavy ions were observed …
Dynamical screening effects on formation of swift heavy ions damage in GaN
P.N. Lebedev Institute of the Russian Academy of Sciences（俄罗斯科学院列别捷夫物理研究所）；Flerov Laboratory of Nuclear Research, Joint Institute for Nuclear Research（俄罗斯联合核研究所弗廖罗夫核研究实验室）；The Institute of Nuclear Physics（核物理研究所）
This review concentrates on the specific properties and characteristics of damage structures generated with high-energy ions in the electronic energy loss regime. Irradiation experiments with so-called swift heavy ions (SHI) find applications in many different fields, with examples presented in ion-track nanotechnology, radiation hardness analysis of functional materials, and laboratory tests of cosmic radiation. The basics of the SHI-solid interaction are described with special attention to processes in the electronic subsystem. The broad spectrum of damage phenomena is exemplified for variou…
Since a few breakthroughs in the fundamental understanding of the effects of swift heavy ions (SHI) decelerating in the electronic stopping regime in the matter have been achieved in the last decade, it motivated us to review the state-of-the-art approaches in the modeling of SHI effects. The SHI track kinetics occurs via several well-separated stages: from attoseconds in ion-impact ionization depositing energy in a target, to femtoseconds of electron transport and hole cascades, to picoseconds of lattice excitation and response, to nanoseconds of atomic relaxation, and even longer macroscopic…
We report depth-resolved photoluminescence measurements of nitrogen-vacancy (NV$^-$) centers formed along the tracks of swift heavy ions (SHIs) in type Ib synthetic single crystal diamonds that had been doped with 100 ppm nitrogen during crystal growth. Analysis of the spectra shows that NV$^-$ centers are formed preferentially within regions where electronic stopping processes dominate and not at the end of the ion range where elastic collisions lead to formation of vacancies and defects. Thermal annealing further increases NV yields after irradiation with SHIs preferentially in regions with …
We experimentally discovered that Al2O3 and MgO exhibit well-pronounced nanometric modifications on the surfaces when irradiated under grazing incidence with 23 MeV I beam, in contrast to normal incidence irradiation with the same ion beam when no damage was found. Moreover, ions in these two materials produce notably different structures: grooves surrounded with nanohillocks on MgO surfaces vs. smoother, roll-like discontinuous structures on the surfaces of Al2O3. To explain these results, detailed numerical simulations were performed. We identified that a presence of the surface inhibits rec…
Formation of swift heavy ion tracks requires extremely fast energy transfer between excited electrons and a lattice. However, electron-phonon energy exchange is too slow, as known from laser-irradiation experiments and calculations. We resolve this contradiction noticing that electron-phonon coupling is not the sole mechanism of energy exchange between electrons and ions: heating of electrons also alters potential energy surface of atoms, accelerating them and increasing their kinetic energy.
