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Diamond-like carbon (DLC) films represent promising surface treatments for biomedical implants. In this paper, using Raman and X-ray photoelectron spectroscopies, we analyzed the effects of secondary phases present in ZrO 2 substrates on the structure of DLC films fabricated by plasma-based ion implantation and deposition method, and the structural stability of the films in response to applied indentation prints. The results revealed oxygen incorporation in DLC films from the oxide substrates during deposition, and a clear dependence of sp3 carbon content on the oxygen fraction of the substrate and on gas pressure. Moreover, a pronounced structural distortion of the DLC films at the film/substrate interface was observed, which resulted from polymorphic transformation on the zirconia surface during deposition, while a pronounced change in Raman spectral morphology of carbon induced by structural alterations could also be observed around the indentation prints. The findings clearly pointed at the need to take into considerations the structural alterations of the DLC film structure at the interface associated with interfacial defects and film adhesion, especially for biomedical applications that involve surface loading. [Display omitted] • Effects of secondary phases in ZrO 2 substrates on the DLC structure were clarified. • Structural stability of the films in response to applied loads was investigated. • Oxygen incorporation in DLC films depended on both substrate and gas pressure. • Phase transformation of zirconia contributed to structural distortion of DLC films. • Structural alterations were induced around the indentation prints on the DLC films. [ABSTRACT FROM AUTHOR]