Sputtering power-driven structural and bonding evolution in vanadium-doped diamond-like carbon films

Abstract Vanadium-doped diamond-like carbon (V-DLC) films were deposited on silicon substrates via DC magnetron sputtering by varying the vanadium target power from 20 W to 100 W. The influence of sputtering power on elemental composition, bonding states, and structural evolution was evaluated by x-ray photoelectron spectroscopy (XPS; survey and high-resolution C 1s/V 2p/O 1s), energy-dispersive x-ray spectroscopy (EDX), and x-ray diffraction (XRD). Elemental analysis revealed a non-linear increase in vanadium content with increasing target power. A significant discrepancy was observed between surface and bulk compositions: XPS indicated a maximum surface vanadium concentration of ∼7.8 at.% at 100 W, whereas EDX revealed a bulk concentration of up to 44.7 at.%. This divergence highlights pronounced surface oxidation. Deconvolution of high-resolution C 1s and V 2p XPS spectra confirmed a distinct structural transition. Films deposited at low powers (20–40 W) retained their amorphous carbon character with a relatively stable sp ² /sp ³ hybrid structure. In contrast, at high powers (70–100 W), the emergence of distinct spectral features at 282.5 eV (C 1s) and a low-binding-energy contribution near 513.5 eV (V 2p) is consistent with V–C bond formation at high target powers, supported by concurrent VC reflections in XRD. Overall, the data indicate a power-driven transition from an amorphous V-DLC network (20–40 W) to an nc-VC/a-C nanocomposite at 70–100 W.