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In this paper, Raman spectral mappings were carried out on Vickers indentation prints introduced on DLC films prepared with different substrate bias voltages (SBV). The mapping results showed clear differences in the intensity ratio, I D / I G , and band shifts for D and G peaks in samples fabricated with and without applying SBV. These spectral characteristics arose from the cumulative effect of a compressive (residual) stress field and structural alterations including sp2 and sp3 carbon disorder upon generation of the indentation print. Additional quantitative stress analyses, which employed spectral line scans on the film cross sections, revealed clear differences in magnitude for the compressive stresses stored in the films, as well as in-depth structural variations resulting from different SBV being applied during fabrication. An increasing level of residual compressive stress in the DLC films with increasing SBV may directly contribute to the observed decreased adhesion to the substrates and to the increased Vickers hardness. Unlabelled Image • Raman mappings were conducted around Vickers indentation prints on DLC films. • Applying SBV showed clear influences on I D / I G , and band shifts for D and G peaks. • Stress and structural alterations influence sp2 and sp3 carbon disorder. • Residual stresses and in-depth structural variations varied with SBV. • Residual compressive stress influenced film adhesion and Vickers hardness. [ABSTRACT FROM AUTHOR]

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]

Abstract Diamond-like carbon films/coatings (DLC) can be employed in a wide range of applications, but the film quality and performance are strongly dependent on the deposition conditions. In this paper, we attempted to clarify the structural and compositional alterations induced by substrate bias voltage (SBV) variation in DLC films by employing different spectroscopic analyses and to correlate them with the variations of two important film properties, hardness and adhesion energy. A series of DLC films fabricated by unbalanced magnetron sputtering with changing substrate bias voltage were investigated by Raman, FTIR and X-ray photoelectron spectroscopies. The results revealed the presence of sp2 and sp3 carbon chains and rings and various types of hydrocarbon in the tetrahedral amorphous carbon films due to incorporation of hydrogen and oxygen. The reduction in hydrogen content together with a generation of sp2 hydrocarbon rings in response to SBV increase were responsible for increases in Young's modulus and hardness, and, concurrently, for a decrease in film adhesion energy. Graphical abstract Unlabelled Image Highlights • Structure & composition of DLC films/Metal grown by UBM were explicitly analyzed. • Applying substrate bias altered DLC microstructures, decreasing sp3 carbon content. • Various types of hydrocarbon were produced by H-incorporation but changed by SBV. • Oxygen incorporation depended on SBV and modified DLC structures and performance. • Modification of hydrocarbon content and structure by SBV determined film adhesion. [ABSTRACT FROM AUTHOR]