Direct Laser Interference Patterning of tetrahedral amorphous carbon films for tribological applications

• Published in: Diamond and related materials Vol. 33; pp. 20 - 26
• Main Authors: Roch, Teja, Weihnacht, Volker, Scheibe, Hans-Joachim, Roch, Aljoscha, Lasagni, Andrés F.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.2013; Elsevier
• Subjects: Ablation; Carbon; Composition and phase identification; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Diamond-like carbon; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; Interference; Laser materials; Laser modification; Lasers; Materials science; Mechanical and acoustical properties; Methods of nanofabrication; Nanoscale pattern formation; Nanostructure; Physical properties of thin films, nonelectronic; Physics; Radiation induced effects; Specific materials; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Tantalum; Thin film structure and morphology; Thresholds; Tribology; Radiation induced effects; Laser materials; Diamond-like carbon; Laser modification; Tribology; Radiation effects; Patterning; Amorphous thin film; Phase transformations; Interference; Mechanical properties; Friction factor; Surface topography; Hardness; Coatings; Thin films; Laser pulse; Crystal-phase transformations; Surface area; Arrays; Graphitization
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2012.12.002

In this work, the influence of surface topography and micro structural changes on the tribological properties of tetrahedral amorphous carbon coatings (ta-C) structured using a holographic technique the direct laser interference pattering (DLIP) is investigated. By utilizing a nanosecond pulsed UV-laser (wavelength 355nm), both ablation and graphitization thresholds were determined as a function of the pulse number. Incubation effects for the ablation threshold (~205mJcm−2) were found to be negligible. However, for the graphitization of the film thresholds varying from 47 to 74mJcm−2 were observed depending on the number of laser pulses utilized (from 1 to 30) and thus obtaining an incubation factor of 1.13. Using two- and three-beam interference setups, dot- and line-like periodic arrays were fabricated. The tribological performance of these patterns was investigated under reciprocating sliding with a ball on disk method under non-lubricated conditions showing that coefficient of friction can be reduced from~0.089 (un-patterned) to~0.055 patterned ta-C (~30% reduction). The results can be explained based on the reduction of surface contact area combined with high hardness as well as the good intrinsic tribological properties of the ta-C films. [Display omitted] ► DLIP of micrometer thick ta-C to fabricate periodic arrays with μm resolution ► Depending on the laser fluence, graphitization and ablation were observed. ► Dot- and line-like patterns were fabricated. ► Surface patterning results in 30% reduced friction of ta-C.