Heteroatom-doped hydrogenated amorphous carbons, a-C:H:X
“Volatile” silicon, sulphur and nitrogen depletion, blue photoluminescence, diffuse interstellar bands and ferro-magnetic carbon grain connections
CNRS, Institut d’Astrophysique Spatiale, UMR 8617,
2 Université Paris Sud, Institut d’Astrophysique Spatiale, UMR 8617, 91405 Orsay, France
Received: 12 April 2013
Accepted: 22 May 2013
Context. Hydrogenated amorphous carbons, a-C:H, can incorporate a variety of heteroatoms, which can lead to interesting effects.
Aims. We investigate the doping of interstellar a-C:H grains with, principally, Si, O, N and S atoms within the astrophysical context.
Methods. A search of the literature on doped a-C:H reveals a number of interesting phenomena of relevance to astrophysics.
Results. X dopants in a-C:H:X materials can affect the sp3/sp2 ratio (X = Si, O and N), lead to blue photoluminescence (undoped or X = N), induce ferromagnetic-like behaviour (X = N and S) or simply be incorporated (depleted) into the structure (X = Si, O, N and S). Si and N atoms could also incorporate into fullerenes, possibly forming colour-centres that could mimic diffuse interstellar bands.
Conclusions. Doped a-C:H grains could explain several dust-related conundrums, such as: “volatile” Si in photo-dissociation regions, S and N depletion in molecular clouds, blue luminescence, some diffuse interstellar bands and ferromagnetism in carbonaceous grains.
Key words: dust, extinction / ISM: general
© ESO, 2013