engleski

Swift Heavy Ion Irradiation Effects in Pre-Damaged Gallium Nitride

*Corresponding author: marko.karlusic@irb.hr When a beam of swift heavy ions (SHI) impinges onto a material, the formation of defects called ion tracks is possible as a result, either in the bulk or on the surface of the material. As a consequence, effects produced by means of SHI irradiation that lead to structural changes of the material can be used to modify the properties of the material via defects engineering. SHI damage introduction to materials can result in complex behavior, especially in radiation harsh environments. To assess the final damage of the material, the effect of the energy deposition from the ions to the atoms within the material must be taken under consideration. Deposition of energy occurs through two main channels: either to the electronic subsystem of the material (electronic stopping power) or to the nuclei (nuclear stopping power). Here we investigate the influence of ion beams with different stopping powers, used in a sequence, on defects formation. It is known that sequential irradiation of ion beams can lead to the SHIBIEC effect (Swift Heavy Ion Beam Induced Epitaxial Crystallization) i.e. the annealing of defects that occurs during the second irradiation step. Alternatively, the anti- SHIBIEC effect is also possible, i.e. the enhanced defect formation during the second step of irradiation. Sequential ion irradiation of GaN has not been investigated so far. This material is an important semiconductor for high-power electronics. The results presented here are of importance for basic research in this field as well. In our previous work [1], we found no evidence of ion track formation in the bulk after SHI irradiation using 23 MeV I and 90 MeV Xe beams. However, recently we were able to introduce additional disorder into moderately damaged GaN crystals using the same 23 MeV I and 90 MeV Xe beams, in cases where GaN samples have been pre-irradiated with 2 MeV Au or with 900 MeV Xe ion beams. Two different ion beams are expected to introduce damage into GaN either by nuclear or electronic stopping, respectively [2, 3]. We observe the difference in total damage in the material depending on the fluence of the beams applied. In this contribution, we report new results of sequential ion irradiation of GaN based on RBS/c (Rutherford Backscattering Spectroscopy in Channeling) and TEM (Transmission Electron Microscopy) measurements. [1] M. Karluši? et al., Response of GaN to energetic ion irradiation - conditions for ion track formation, J. Phys. D: Appl. Phys. 48 (2015) 325304 [2] S.O. Kucheyev et al., Ion implantation into GaN, Mat. Sci. Eng. 33 (2001) 51 [3] M. Sall et al., Track formation in III-N semiconductors irradiated by swift heavy ions and fullerene and re-evaluation of the inelastic thermal spike model, J. Mater. Sci. (2015) 50:5214–5227

Defects ; Rutherford Backscattering ; Ion-Beam processing

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