Water Adsorption on Phosphorous-Carbide Thin Films

E. BROITMAN2, A. FURLAN, G.K. GUEORGUIEV, ZS. CZIGÁNY, A. M. TARDITI, A.J. GELLMAN, S. STAFSTRÖM, L. HULTMAN

San Diego, California, USA

Congreso; 36th International Conference On Metallurgical Coatings And Thin Films ICMCTF 2009; 2009

Amorphous phosphorous-carbide films have been considered as a new tribologicalcoating material with unique electrical properties. However, the coatings cannot bepractically used until now because CPx films rapidly oxidize/hydrolyze and delaminatewhen in contact with air. Recently we demonstrated that CPx thin solid films with afullerene-like structure can be deposited by magnetron sputtering. Thus, the introductionof P atoms in the graphene structure induces the formation of bent and interlinkedgrapheme planes.1,2 In this work we compare the uptake of water of amorphousphosphorous-carbide (a-CPx) films, with fullerene-like phosphorous-carbide (FL-CPx)and amorphous carbon (a-C) films. Films with thickness in the range 100-300 nm weredeposited on on silicon, quartz and gallium orthophosphate substrates by reactive DCmagnetron sputtering. The film microstructure was characterized by X-ray photoelectronspectroscopy, and transmission electron microscopy and diffraction. A piezoelectriccrystal microbalance placed in a vacuum chamber as described in Ref 3 was used tomeasure their water adsorption. Measurements indicate that the amount of adsorbed wateris highest for the pure a-C films and that the FL-CPx films adsorbed less water than a-CPx. To provide additional insight into the atomic structure of defects in the FL-CPx, a-CPx and a-C compounds, we performed first-principles calculations within the frameworkof Density Functional Theory. Emphasis was put on the energy cost for formation ofvacancy defects and dangling bonds in relaxed systems.3 Cohesive energy comparisonreveals that the energy cost formation for dangling bonds in different configurations isconsiderable higher in FL-CPx than for the amorphous films. These simulations thusconfirm the experimental results that dangling bonds are less likely in FL-CPx than in a-CPx and a-C films.1 A. Furlan, G.K. Gueorguiev