To further investigate the fragmentation behaviour of the beta-diketonate copper precursors, OES spectra from a time-resolved e-CVD cycle using Cu(acac)₂ were compared to those obtained with Cu(hfac)₂, as shown in Fig. . Spectral lines indicating Cu ions were detected only when using Cu(hfac)₂, suggesting that the Cu(acac)2 molecule is more stable during plasma exposure. Thus, while a beta-diketonate ligand without fluorine or chlorine could be viable for e-CVD, achieving efficient surface reduction would likely require higher electron temperatures to produce adequate free Cu ions.