Water adsorption on phosphorous-carbide thin films

✍ Scribed by E. Broitman; A. Furlan; G.K. Gueorguiev; Zs. Czigány; A.M. Tarditi; A.J. Gellman; S. Stafström; L. Hultman

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 793 KB
• Volume: 204
• Category: Article
• ISSN: 0257-8972
• DOI: 10.1016/j.surfcoat.2009.06.003

✦ Synopsis

Amorphous phosphorous-carbide films have been considered as a new tribological coating material with unique electrical properties. However, such CP x films have not found practical use until now because they tend to oxidize/hydrolyze rapidly when in contact with air. Recently, we demonstrated that CP x thin films with a fullerene-like structure can be deposited by magnetron sputtering, whereby the structural incorporation of P atoms induces the formation of strongly bent and inter-linked graphene planes. Here, we compare the uptake of water in fullerene-like phosphorous-carbide (FL-CP x ) thin films with that in amorphous phosphorous-carbide (a-CP x ), and amorphous carbon (a-C) thin films. Films of each material were deposited on quartz crystal substrates by reactive DC magnetron sputtering to a thickness in the range 100-300 nm. The film microstructure was characterized by X-ray photoelectron spectroscopy, and high resolution transmission electron microscopy. A quartz crystal microbalance placed in a vacuum chamber was used to measure their water adsorption. Measurements indicate that FL-CP x films adsorbed less water than the a-CP x and a-C ones. To provide additional insight into the atomic structure of defects in the FL-CP x and a-CP x compounds, we performed first-principles calculations within the framework of density functional theory. Cohesive energy comparison reveals that the energy cost formation for dangling bonds in different configurations is considerably higher in FL-CP x than for the amorphous films. Thus, the modeling confirms the experimental results that dangling bonds are less likely in FL-CP x than in a-CP x and a-C films.