The OES results (Fig. ) suggest that the fluorine contamination in the thin films likely comes from redeposition during the plasma pulse. To address this, experiments were conducted using Cu(acac)₂, a fluorine-free version of the Cu(hfac)₂ molecule, as detailed in the supplementary material. Notably, films deposited with Cu(acac)₂ exhibited comparable carbon content to those prepared with Cu(hfac)₂, as shown in Fig. . This observation indicates that both precursor molecules may generate similar fragment species under plasma exposure, which then adsorb onto the film surface.