Optical spectroscopy study of damage induced in 4H-SiC by swift heavy ion irradiation

Abstract

Single crystals of 4H-SiC were irradiated with swift heavy ions (332 MeV Ti, 106 MeV Pb and 2.7 GeV U) in the electronic energy loss regime. The resulting damage was investigated with UV-visible optical absorption spectroscopy and micro-Raman spectroscopy. The evolution of the Raman data with fluence shows an accumulation of isolated point defects without amorphization of the material and a partial recrystallization of the structure, but only at the lowest fluence. Furthermore, the longitudinal optical phonon-plasmon coupling mode disappears upon irradiation, suggesting a strong perturbation of the electronic structure. This evolution is consistent with the optical bandgap decrease and the Urbach edge broadening that was also previously observed for the irradiation with 4 MeV Au ions.

Effect of Xe ion (167 MeV) irradiation on polycrystalline SiC implanted with Kr and Xe at room temperature

“…This means that the crystal structure is continuous from the bulk up to the amorphous region and thus the recrystallization was epitaxial. Similar recrystallization results have been reported [16][17][18][19][20][21][22][23] for both 33 keV/nm and 20 keV/nm electronic energy losses at fluences below 10 14 cm -2 . A very high density of planar defects is also visible in the SHI irradiated specimen and accompanying diffraction pattern.…”

“…Investigations on the creation of radiation damage in SiC by SHI irradiation and the annealing of radiation damage retained after implanting different low energy ions have been reported recently [16][17][18][19][20][21][22][23]. These studies seem to agree that SHI irradiation leads to point defect production in SiC and partially restores crystallinity in a heavily damaged SiC.…”

Graphitic nanostripes in silicon carbide surfaces created by swift heavy ion irradiation

“…Thus, in the electronic stopping regime, irradiation with dE/dx below this threshold will induce only isolated point defects. Depending on the fluence, these point defects can accumulate but this will still not give rise to complete amorphization of the material 22 . Instead, it has been observed that even a recrystallization of the defective structure may occur.…”

“…Instead, it has been observed that even a recrystallization of the defective structure may occur. This damage recovery has been attributed to the competing effects due to nuclear collisions and electronic excitations [22][23][24] . These findings however impose a severe limitation on SHI irradiation as a tool for defect engineering of SiC.…”

Structural and defects induced phenomena in γ-rays irradiated 6H-SiC

“…It has been demonstrated that SiC is not sensitive to ionization processes and only a small concentration of point defects is produced in this material under such irradiation conditions [34][35]. Some of the reported experimental observations in the current contribution are somehow different.…”