Modification of C-doped a-SiO2 after Swift Heavy-Ion Irradiation

Zhi-Guang Wang,Cun-Bao Liu,Hang Zang,Kong-Fang Wei,Cun-Feng Yao 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.6

Amorphous SiO2 (a-SiO2) thin films were thermally grown on single-crystalline silicon. These a-SiO2/Si samples were first implanted (C-doped) with 100-keV carbon ion at room temperature (RT) at a dose of 5.0 × 1017 C-ions/cm2 and were then irradiated at RT by using 853 MeV Pb ions at doses of 5.0 × 1011, 1.0 × 1012, 2.0 × 1012, and 5.0 × 1012 Pb-ions/cm2, respectively. The microstructures and the photoluminescence (PL) properties of these samples induced by Pb ions were investigated using fluorescence spectroscopy and transmission electron microscopy. We found that high-energy Pb-ion irradiation could induce the formation of a new phase and a change in the PL property of C-doped a-SiO2/Si samples. The relationship between the observed phenomena and the ion irradiation parameters is briefly discussed. Amorphous SiO2 (a-SiO2) thin films were thermally grown on single-crystalline silicon. These a-SiO2/Si samples were first implanted (C-doped) with 100-keV carbon ion at room temperature (RT) at a dose of 5.0 × 1017 C-ions/cm2 and were then irradiated at RT by using 853 MeV Pb ions at doses of 5.0 × 1011, 1.0 × 1012, 2.0 × 1012, and 5.0 × 1012 Pb-ions/cm2, respectively. The microstructures and the photoluminescence (PL) properties of these samples induced by Pb ions were investigated using fluorescence spectroscopy and transmission electron microscopy. We found that high-energy Pb-ion irradiation could induce the formation of a new phase and a change in the PL property of C-doped a-SiO2/Si samples. The relationship between the observed phenomena and the ion irradiation parameters is briefly discussed.

Emulation of Radiation Damage in Al-B4C Neutron Absorber Used in Temporary/Interim Spent Nuclear Fuel Storage Facility

Woong Ha,Sangjoon Ahn 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

Al-B4C neutron absorbers are currently widely used to maintain the subcriticality of both wet and dry storage facilities of spent nuclear fuel (SNF), thus long-term and high-temperature material integrity of the absorbers has to be guaranteed for the expected operation periods of those facilities. Surface corrosion solely has been the main issue for the absorber performance and safety; however, the possibility of irradiation-assisted degradation has been recently suggested from an investigation on Al-B4C surveillance coupons used in a Korean spent nuclear fuel pool (SFP). Larger radiation damage than expectation was speculated to be induced from 10B(n, α)7Li reactions, which emit about a MeV α-particles and Li ions. In this study, we experimentally emulated the radiation damage accumulated in an Al-B4C neutron absorber utilizing heavy-ion accelerator. The absorber specimens were irradiated with He ions at various estimated system temperatures for a model SNF storage facility (room temperature, 150, 270, and 400°C). Through the in-situ heated ion irradiation, three exponentially increasing level of radiation damages (0.01, 0.1, and 1 dpa or displacement per atom) were achieved to compare differential gas bubble formation at near surface of the absorber, which could cause premature absorber corrosion and subsequential 10B loss in an SNF storage system. An extremely high radiation damage (10 dpa), which is unlikely achievable during a dry storage period, was also emulated through high temperature irradiation (350°C) to further test the radiation resistance of the absorber, conservatively. The irradiated specimens were characterized using HR-TEM and the average size and number density of radiation-induced He bubbles were measured from the obtained bright field (BF) TEM micrographs. Measured helium bubble sizes tend to increase with increasing system (or irradiation) temperature while decrease in their number density. Helium bubbles were found from even the lowest radiation damage specimens (0.01 dpa). Bubble coalescence was significant at grain boundaries and the irradiated specimen morphology was particularly similar with the bubble morphology observed at the interface between aluminum alloy matrix and B4C particle of the surveillance coupons. These characterized irradiated specimens will be used for the corrosion test with high-temperature humid gas to further study the irradiation-assisted degradation mechanism of the absorber in dry SNF storage system.

MeV carbon ion irradiation-induced changes in the electrical conductivity of silver nanowire networks

Bushra Bari,Shehla Honey,Madhuku Morgan,Ishaq Ahmad,Rauf Khan,Arshad Muhammad,Khalid Alamgir,Shahzad Naseem,Maaza Malik 한국물리학회 2015 Current Applied Physics Vol.15 No.5

MeV carbon ion irradiation-induced changes in the electrical conductivity of Silver nanowire (Ag-NW) networks is demonstrated systematically at different C+ ion fluences ranging from 1 × 1012 to 1 × 1016 ions/cm2 at room temperature. At low C+ ion fluences, the electrical conductivity of Ag-NWs decreases and subsequently increases with increase fluence. Finally, at high C+ ion fluences, conductivity again decreases. The variation in the electrical conductivity of Ag NW network is discussed after analysis using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The observed increase in electrical conductivity is thought to be due to ion induced coalescence of Ag-NWs at contact position, which causes reduction of wire-wire contact resistance, while the decrease in electrical conductivity may be due to defect production by C+ ions into Ag-NWs. Ion beam technology is therefore a very promising technology that is capable of fabricating highly conductive Ag-NW networks for transparent electrodes. Moreover, a method for thinning, slicing and cutting of Ag-NWs using ion beam technology is also reported.

Effect of thermal annealing on low-energy C-ion irradiated MgB₂ thin films

Jung, Soon-Gil,Son, Seung-Ku,Pham, Duong,Lim, W.C.,Song, J.,Kang, W.N.,Park, T. The Korea Institute of Applied Superconductivity a 2019 한국초전도저온공학회논문지 Vol.21 No.3

We investigate the effect of thermal annealing on $MgB_2$ thin films with thicknesses of 400 and 800 nm, irradiated by 350 keV C-ions with a dose of $1{\times}10^{15}atoms/cm^2$. Irradiation by low-energy C-ions produces atomic lattice displacement in $MgB_2$ thin films, improving magnetic field performance of critical current density ($J_c$) while reducing the superconducting transition temperature ($T_c$). Interestingly, the lattice displacement and the $T_c$ are gradually restored to the original values with increasing thermal annealing temperature. In addition, the magnetic field dependence of $J_c$ also returns to that of the pristine state together with the restoration of $T_c$. Because $J_c$(H) is sensitive to the type and density of the disorder, i.e. vortex pinning, the recovery of $J_c$(H) in irradiated $MgB_2$ thin films by thermal annealing indicates that low-energy C-ion irradiation on $MgB_2$ thin films primarily causes lattice displacement. These results provide new insights into the application of low-energy irradiation in strategically engineering critical properties of superconductors.

Effect of thermal annealing on low-energy C-ion irradiated MgB2 thin films

정순길,Seung-Ku Son,Duong Pham,W. C. Lim,J. Song,W. N. Kang,T. Park 한국초전도.저온공학회 2019 한국초전도저온공학회논문지 Vol.21 No.3

We investigate the effect of thermal annealing on MgB2 thin films with thicknesses of 400 and 800 nm, irradiated by 350 keV C-ions with a dose of 1 ´ 1015 atoms/cm2. Irradiation by low-energy C-ions produces atomic lattice displacement in MgB2 thin films, improving magnetic field performance of critical current density (Jc) while reducing the superconducting transition temperature (Tc). Interestingly, the lattice displacement and the Tc are gradually restored to the original values with increasing thermal annealing temperature. In addition, the magnetic field dependence of Jc also returns to that of the pristine state together with the restoration of Tc. Because Jc(H) is sensitive to the type and density of the disorder, i.e. vortex pinning, the recovery of Jc(H) in irradiated MgB2 thin films by thermal annealing indicates that low-energy C-ion irradiation on MgB2 thin films primarily causes lattice displacement. These results provide new insights into the application of low-energy irradiation in strategically engineering critical properties of superconductors.