Publication Date:
2014-12-13
Description:
Publication date: February 2015 Source: Vacuum, Volume 112 Author(s): G.A. Viana , F.C. Marques Structural and thermodynamic properties of xenon incorporated in amorphous carbon films deposited by means of a sputtering system free of vacuum pumping during the deposition were investigated by visible Raman (Vis–Raman) scattering and thermal desorption spectroscopy (TDS), respectively. Vis–Raman measurements, carried out before and after the xenon desorption, revealed a polycrystalline material rich in C-sp 2 sites that form randomly dispersed nanosized graphite clusters (nanocrystals) of approximately 1 nm. After xenon desorption, a compensating mechanism, activated by the thermal heating, promotes a more ordered C-sp 2 network as revealed by the linewidths of both D and G bands, as well as by the I D / I G ratio evolution. The TDS thermograms show that the xenon onset effusing temperature is approximately 120 °C. Besides, they also revealed two different regimes, at low and at high temperatures, associated with desorption of xenon atoms trapped either in an interconnecting void network or within the graphite nanocrystals. From the latter regime, the xenon diffusion free energy (activation energy) was determined to be 1.2 eV (115.7 kJ/mol) on the basis of the diffusion-limited desorption standard model.
Print ISSN:
0042-207X
Electronic ISSN:
1879-2715
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
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