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Carbon films have been produced by accelerating C60 þ ions on silicon substrates with energies between 100 and 800 eV. Furthermore some samples have been vacuum-annealed at 600 8C. The samples have been characterized by Raman and positron annihilation spectroscopies (RS‐PAS). The measurements for the as-deposited material show that there is a coexistence of polymerized fullerenes and amorphous-carbon islands and that the structure depends on the energy of the incident ions. At low energies, fullerenes are deposited preserving the molecular identity and some intermolecular covalent bonds begin to insinuate; at higher energies, the amount of these covalent bonds increases and the amorphous islands predominate. After the annealing process, the amorphous phase organizes in graphitic clusters and the unbroken C60 cages are transformed back to pristine and slightly polymerized C60. # 2003 Elsevier Science B.V. All rights reserved.

Amorphous Si x C 1− x (a-Si x C 1− x ) films with x ranging from 0 to 0.4 have been produced using a high energy ion beam deposition method. The resulting films have been characterized by Raman annihilation spectroscopy and positron annihilation spectroscopy (PAS). Hardness and wear resistance have also been measured. It has been shown that the open volume defects and their distribution through the films have an important role in determining the mechanical behavior of the as-deposited and thermal treated films.

A compact ion source has been designed for use in the production of amorphous carbon thin films with diamond-like properties. This filament-discharge ion source works very efficiently at a low input electrical power. The design, which is simple and reliable, has some features that makes it distinct from that of the multicusp and plasma discharge ion sources. We have achieved a transportable beam with a current density of 100 mA cm −2 delivered by a filament-discharge power of 150 W. The final goal of this development is associated to the design of a particle accelerator for applications that require high beam intensities, like the boron neutron capture therapy.

Amorphous Si x C 1− x films, with x ranging from 0.30 to 0.70, were grown by high-energy ion beam deposition starting from a methane–silane gas mixture. XPS analysis of the samples shows that it is possible to incorporate silicon to the amorphous carbon matrix giving an Si/C ratio depending on the methane–silane gas mixture. Raman spectra of the thermally annealed films indicate that the silicon incorporation in a-C films increases their thermal stability. There is no evidence of a complete graphitization up to 900°C, while in a-C samples graphitization occurs at about 500°C. This result shows that thermal stability is a function of the film composition.

Hard amorphous carbon films produced using high-energy (ca. 30 keV) ion beam deposition of CH 3 + and CH 4 + on silicon wafers, have been investigated by Positron Annihilation Spectroscopy (PAS), the results are correlated with Raman Spectroscopy and Electrical Resistivity measurements. The microstructural modifications of the films as a function of the annealing temperature in the 300–600°C range have been studied. The evolution of the fractions of sp 2 and sp 3 bonds is described and related to the changes of the open volume defect distribution and the graphitization process.

Amorphous Si1−xCx films, with x ranging from 0.54 to 0.71 and low hydrogen content (less than 5%) were grown by high-energy hydrocarbon ion beam deposition on silicon wafers. The resulting films were studied using XPS, AES, EELS and Raman spectroscopies. As x increases there is a higher number of C atoms in sp2 sites, showing that for high carbon concentrations the bonding character of the C atoms is a function of the Si/C relative content in the films. Films annealed at different temperatures were studied by Raman and XPS spectroscopies; there is no evidence of a complete graphitization up to 900°C. It is concluded that the presence of Si in the films increases their thermal stability.

We report a characterization of hard amorphous carbon films prepared by a new method: high-energy (ca. 30 keV) bombardment with CH 3 + and CH 4 + ions. The results of AES and EELS reveal that almost 60% of the atoms are in sp 2 sites and are consistent with the hypothesis that the microscopic structure of the films consists of an intricate network of small amorphous graphite-like sheets connected by sp 3 -rich zones. Raman spectroscopy and SIMS results are also discussed.

Deposition of diamond-like thin films has been achieved using mass-separated C+, CH+3 and CH+4 ion beams of energies between 1 and 40 keV. Characterization using different methods shows that the structure and physical properties of the films obtained are closer to those of diamond when 30–40 keV CH+3 or CH+4 ion beams are used. The hydrogen concentration, measured with elastic recoil detection analysis, is lower than 1 at.% for all the 30 keV hydrocarbon beams used.

A description for the different phase transitions in crystalline bromoform is proposed. Making use of simple intermolecular potentials, the transition from the hexagonal γ phase to the triclinic β phase can be explained in terms of a relative slipping between semirigid bilayers, in agreement with experimental evidence. The order-disorder α↔γ phase transition is described in the mean field approximation, and the critical temperature is explicitly related to the intermolecular interactions. The α↔β phase transition, analyzed via free energy curves, is associated to the entropy change due to orientational disorder. The results predict the possible existence of two other hexagonal phases, not experimentally observed.

A characterization of carbon films prepared by bombarding a substrate with high‐energy (∼40 keV) CH+n ions is reported. We have found that although the hardness, wear resistance, transparency and electrical resistivity of the films are similar to those of diamonds, the results of EELS and SIMS experiments reveal that the microscopic structure is very similar to that of graphite. From the measured plasmon energies we determine the film densities and from the K‐edge loss region we determine the ratio of C atoms in sp2 and sp3 sites.