Silver surface segregation in Ag-DLC nanocomposite coatings

• Published in: Surface & coatings technology Vol. 267; pp. 90 - 97
• Main Authors: Manninen, Noora Kristiina, Galindo, Ramon Escobar, Carvalho, Sandra, Cavaleiro, Albano
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-04-2015
• Subjects: Ag surface segregation; Ag-alloyed DLC; Carbon; Coatings; Deposition; DLC; magnetron sputtering; morphology; Multilayers; Nanocomposites; Nanostructure; Scanning electron microscopy; Silver; magnetron sputtering; DLC; morphology; Ag-alloyed DLC; Ag surface segregation
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2014.12.029

AgDLC coatings were deposited by magnetron sputtering in order to evaluate: i) the Ag nanoparticle size distribution along the coatings thickness and ii) the silver stability in DLC coatings. Four different coatings were deposited, two AgDLC nanocomposite coatings containing 20at.% of Ag, with thicknesses of 250nm and 1000nm, a 250nm AgDLC nanocomposite coating with carbon barrier layer of 75nm and a multilayer coating, consisting of a pure Ag layer with a carbon barrier layer of 75nm. The coatings were characterized with respect to their structure (by means of X-ray diffraction (XRD)), morphology (by scanning electron microscopy (SEM)) and Ag distribution in depth (by glow discharge optical emission spectroscopy (GDOES)). The AgDLC nanocomposite coatings are composed of Ag nanograins (with a size of about 3nm) dispersed in an amorphous carbon matrix. The SEM results suggest a bimodal size distribution along the coatings thickness, it was found that Ag forms nanoparticles and aggregates with sizes ranging from 14nm up to 52nm on the coating's surface, whereas in bulk, no Ag nanoparticles were visible by SEM. The monitoring of the Ag stability at room temperature conditions during a period of 6months showed that Ag segregates to the coatings surface, in the AgDLC nanocomposite coating with 1000nm forming Ag nanofibers, while the thinner AgDLC (250nm) as well as the multilayer (Ag+DLC and AgDLC+DLC) coatings were stable over time.
•Analysis of the distribution of Ag nanoparticles through the coatings thickness.•Silver segregation to the AgDLC coatings surface at room temperature conditions.•Importance of the carbon matrix morphology on the control of Ag segregation.