Superior hardness and Young's modulus of low temperature nanocrystalline diamond coatings

• Published in: Materials chemistry and physics Vol. 144; no. 3; pp. 505 - 511
• Main Authors: Cicala, G., Magaletti, V., Senesi, G.S., Carbone, G., Altamura, D., Giannini, C., Bartali, R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-04-2014
• Subjects: AFM; Carbon content; Coatings; Deposition; Grain size; Grazing incidence x-ray diffraction; Hardness; Mechanical properties; Modulus of elasticity; Morphology; Nanocrystals; Nanostructures; Plasma deposition; Silicon substrates; Surface properties; Mechanical properties; AFM; Nanostructures; Coatings; Grazing incidence x-ray diffraction; Plasma deposition
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2014.01.027

Nanocrystalline diamond (NCD) coatings with thickness of about 3 μm were grown on silicon substrates at four deposition temperatures ranging from 653 to 884 °C in CH4/H2/Ar microwave plasmas. The morphology, structure, chemical composition and mechanical and surface properties were studied by means of Atomic Force Microscopy (AFM), X-Ray Diffraction (XRD), Raman spectroscopy, nanoindentation and Water Contact Angle (WCA) techniques. The different deposition temperatures used enabled to modulate the chemical, structural and mechanical NCD properties, in particular the grain size and the shape. The characterization measurements revealed a relatively smooth surface morphology with a variable grain size, which affected the incorporated hydrogen amount and the sp2 carbon content, and, as a consequence, the mechanical properties. Specifically, the hydrogen content decreased by increasing the grain size, whereas the sp2 carbon content increased. The highest values of hardness (121 ± 25 GPa) and elastic modulus (1036 ± 163 GPa) were achieved in NCD film grown at the lowest value of deposition temperature, which favored the formation of elongated nanocrystallites characterized by improved hydrophobic surface properties.
•We produce the hardest NCD coating at the lowest deposition temperature.•We modify the deposition temperature to tailor the grain size and shape of the NCD coatings.•We assess the mechanical properties (hardness and elastic modulus) of superhard NCD coating on a soft silicon substrate.