ADSORPTION OF BENZENE ON POROUS AMORPHOUS HYDROGENATED CARBON-FILMS

The annealing effect on porosity of amorphous hydrogenated carbon thin films was studied using a quartz crystal microbalance. As-prepared films show a mesoporous structure and a low adsorption capacity which is proportional to film thickness. Porosity of the as-prepared film is estimated at about 0.15. Baking in vacuum changes the film to be highly microporous and significantly increases the porosity of the films to over 0.40, depending annealing history. Outgassing during the annealing process plays an important role in the formation of porosity. Heat treatment first opens micropores in the slightly mesoporous film. Further heating increases the number and size of micropores, and also produces mesopores. With prolonged heating at high temperatures, further outgassing occurs, resulting in collapsing of the films.