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Electron impact ionisation of iso-octane is studied using mass spectrometry. Cross-sections for the formation of fragment ions are measured between 17 and 79 eV. C4H9+ is the most abundant ion, C8H18+ is completely absent. A total ionisation cross-section of 2×10−15 cm2 is found at 79 eV. Ab initio calculations show that the principal ionic species observed, C4H9+, C4H8+, C7H15+, C3H6+ and C3H11+, may be issued directly from iso-octane by simple C–C bond split processes or with H atom rearrangements. Ionisation of the two major neutral species issued from bond split, C4H9 and C4H10, can lead to the principal ions observed.

Hydrogenated amorphous carbon and carbon nitride films (a-C1−xNx:H) have been synthesized from methane, acetylene, or acetylene–nitrogen precursor gases using a high density electron cyclotron resonance plasma. The deposition and etching rates, along with the film stoichiometry, density, Raman signature of the sp2 phase, and optical and transport properties, have been studied as a function of plasma parameters (microwave power and negative bias of the substrate). While low-density H-rich carbon films have been grown from methane for ion energies up to 200 eV, films grown using acetylene have been obtained at high deposition rate (1.1 nm s−1) with H content below 25 H at. % and density of 2.0 g cm−3, which makes them interesting as electronic materials. For dense carbon nitride alloys, the maximum (N/N+C)=0.35 is limited by the vanishing growth rate, which results from ion-assisted chemical etching mechanisms. A larger N2 plasma etching rate related with lower film density is observed for (N/N+C) values ab...