TITLE

Thermal gas effusion from hydrogenated amorphous carbon films

AUTHOR(S)
Wild, Ch.; Koidl, P.
PUB. DATE
November 1987
SOURCE
Applied Physics Letters;11/9/1987, Vol. 51 Issue 19, p1506
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
Hydrogenated amorphous carbon (a-C:H) films, deposited onto negatively biased substrates in a 13.56-MHz hydrocarbon glow discharge system, have been investigated by mass spectroscopic thermal effusion measurements. Depending on the bias voltage UB as the most important deposition parameter, hydrocarbons and/or H2 molecules are desorbed at threshold temperatures between 300 and 600 °C. The threshold temperature increases with increasing bias voltage while the mass of the desorbed molecules decreases. a-C:H films deposited at low bias release H2, CH4, and higher hydrocarbons whereas from hard a-C:H films deposited at UB>=500 V, only H2 is released. Using double-layer a-C:H/a-C:D films, it is shown that H2 and CH4 molecules are formed in the volume of the film followed by molecular diffusion through the a-C:H network. For high-bias voltages (UB>=500 V), the reduced pore size of the strongly crosslinked a-C:H network is shown to prevent diffusion of hydrocarbon molecules, while the films are still permeable for hydrogen.
ACCESSION #
9824853

 

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