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Highly oriented pyrolytic graphite (HOPG) structural changes caused by gallium (Ga) implantation at room temperature were investigated. Ga ions were implanted into HOPG at different energies (10, 20, and 30 keV) and fluences (ranging from 2×10^15 to 5×10^16 Ga+/cm²). To monitor structural changes in the samples post-implantation, Raman spectroscopy was employed. The Raman spectra of the pristine HOPG sample displayed low-intensity D peaks at 1359 cm⁻¹ and high-intensity G peaks at 1582 cm⁻¹. After implantation with 10 keV at a fluence of 5×10^16 Ga+/cm², a decrease in G peak intensity was observed, accompanied by an increase in its full width at half maximum (FWHM), indicating defect formation in the HOPG structure. In contrast, implantation with 30 keV at the same fluence (5×10^16 Ga+/cm²) resulted in the merging of the D and G peaks into a broad peak, signifying the amorphization of HOPG. These results confirm that ion energy plays a significant role in the amorphization of HOPG. Furthermore, implantation with 20 keV Ga ions at fluences ≤2×10^16 Ga+/cm² introduced some defects in the HOPG structure, while higher fluences (≥4×10 16 Ga + /cm²) led to complete amorphization. It appears that the threshold displacement per atom (dpa) required to amorphize the HOPG used in this study is higher than 35 dpa, significantly exceeding the previously suggested range of 0.2 dpa to 3 dpa. The findings of this study align with very few prior results, where no amorphization was observed above 3 dpa. However, further research and testing are necessary to quantify the dpa required for HOPG amorphization.
