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The sputtering behaviour of CaF₂ thin films produced on Si and graphite substrates was studied in this paper. The study seeks to clarify the role of substrate material, specifically conductive versus semiconductive and structurally different surfaces, on the sputtering yield and surface modification of CaF₂. Thin films of CaF₂ were deposited on both substrates using an e-beam deposition method and irradiated at room and low temperatures under high vacuum, using 20 MeV Cu⁵⁺ ions. After-irradiation examination using 2 MeV He²⁺ beam on Rutherford backscattering spectrometry (RBS) was carried out. Atomic force microscopy (AFM) and Raman spectroscopy found significant differences in sputtering yields and morphological alterations. The CaF₂ layer on graphite has a higher effective sputtering yield than on silicon due to differences in electronic stopping power, thermal conductivity, and interfacial bonding. Surface examination revealed preferential fluorine depletion and the formation of nanoscale hillocks and craters on both substrates, with graphite-supported films exhibiting more pronounced surface roughening. The study found that the substrate has a crucial role in the kinetics of ion-beam-induced sputtering in CaF₂. This has potential implications for radiation-resistant coatings and optical devices.
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