Ye Li

Single-phase concentrated solid-solution alloys have garnered widespread attention due to their remarkable irradiation resistance properties. In this study, the molecular dynamics method was employed to investigate the collision cascade process in Ni–Fe alloys. The generation and evolution of point defects under uniaxial strain were systematically analyzed for alloys with varying Fe concentrations. It was observed that the peak number of point defects increased under tensile strain but decreased under compressive strain as the uniaxial strain magnitude rose. However, the uniaxial strain exhibited only a minor influence on the surviving number of defects. The calculated formation energies revealed that Fe vacancies possessed higher formation energies compared to Ni vacancies. Consequently, an increase in Fe concentration led to greater participation of Fe atoms in collision cascades, resulting in fewer point defects during the thermal peak stage. Owing to the elevated defect formation energies of Fe relative to Ni, the proportions of Fe vacancies and interstitials in the total point defects were consistently lower than the Fe atomic concentration. These findings indicate that higher Fe concentrations impede the formation of point defects.

With the molecular dynamics method, this paper investigates radiation-induced defects in the In_0.16Ga_0.84N/GaN superlattice structure (SLS) and the In_0.04Ga_0.96N/GaN SLS. In the temporal evolution of cascades, most of vacancies recombine with interstitials. The Monte Carlo simulations about the proportions of PKAs induced by 3 MeV protons were also considered in this work for calculating the weighted averages of surviving defects. For the In_0.16Ga_0.84N/GaN SLS irradiated by protons, around 82.6 percent of surviving vacancies are Ga vacancies while around 88.9 percent of surviving interstitials are Ga interstitials. For the In_0.04Ga_0.96N/GaN SLS irradiated by protons, around 87.3 percent of surviving vacancies are Ga vacancies while around 88.6 percent of surviving interstitials are Ga interstitials. N vacancies, N interstitials, and In vacancies also exist in irradiated InGaN/GaN SLS. Details about different types of defects are presented in this paper, which helps explain the microscopic mechanism of irradiated InGaN/GaN SLS. Since different types of defects have different influences on electronic and optical properties, simulations about the proportions of various defects in irradiated InGaN/GaN SLS help experimentalists find the effective factors of radiation-related changes in electronic and optical properties.

Using first-principles calculations, we studied the formation energy of point defects in cubic silicon carbide (3C-SiC) and the influences of defects on its electronic band structure, density of states, and optical properties. We found that the formation energy of the interstitial defect is greater than that of the vacancy and antisite defect, with the Si interstitial defect having the highest formation energy. The electronic band structure and density of states have no bandgap due to the vacancy defect, interstitial defect, and Si antisite defect (Si atom occupies the position of C atom), while the changes due to the C antisite defect (C atom occupies the position of Si atom) are not significant. Depending on the type of defect, the optical properties change differently, with the vacancy defect having the most significant impact on the optical properties. The vacancy defect notably increases the optical conductivity, dielectric function, reflectivity, extinction coefficient, and refractive index in the low-energy region, indicating the potential application of 3C-SiC in the field of optoelectronic devices.

Irradiated In _0.32 Ga _0.68 N in previous research showed temperature-dependent changes in Raman spectra, which indicates the crucial role of temperature in the evolution of cascades. To reveal the atomic-scale reason for temperature-dependent changes in Raman spectra, this paper investigates the overlapping cascades in irradiated In _0.25 Ga _0.75 N and In _0.32 Ga _0.68 N at different temperatures with the molecular dynamics method. The presented results indicate that defects in irradiated samples at elevated temperatures experienced enhanced atomic recombination in overlapping cascades. The temperature-dependent defects in In _0.32 Ga _0.68 N relate to the temperature-dependent shift of peaks A ^LO ₁ and E ^LO ₁ in Raman spectra by the LO phonon-plasmon coupling. The distribution of Ga clusters, N clusters, and In clusters is expected to have additional effects on localized electron carrier concentration which further influences the wavenumbers of peaks A ^LO ₁ and E ^LO ₁ in Raman spectra. The presented results provide academic support for reducing the defect production rate of the ion implantation doping technique at elevated temperatures.