Data on the hydrogen release from a-C:H induced by ion irradiation have been analyzed using a statistical model based on bulk molecular recombination. Good fits were obtained for all available data by adjusting a single parameter which is correlated to the stopping power of the projectile in the material.

Energetic ion-beam irradiation of diamondlike carbon thin films induces a decrease of 5–6 orders of magnitude in the resistivity of the films from their as-grown value of 107 Ω cm. Diagnostics used to characterize the nature of the transformation included optical absorption measurements (band gap), Raman spectroscopy (microcrystalline structure), Rutherford backscattering spectroscopy (hydrogen content of the films), and measurements of the temperature dependence of the conductivity (electronic structure). It was found that the initial decrease in resistivity with an increasing ion dose is due to the loss of hydrogen from the films, with a concomitant decrease in the optical band gap. Heating the films during the irradiation greatly accelerates the rate of hydrogen loss as a function of dose. Once the hydrogen removal is complete, further irradiation increases the film conductivity by inducing the growth of microcrystallites of graphite.

The removal of defects in diamond by light-ion bombardment has been studied by means of Rutherford backscattering spectroscopy (RBS) channeling techniques. The damage produced by 1 × 1014 Sb ions cm−2 at 300 keV (below the critical dose for graphitization) was observed to diminish by as much as 50% under bombardment with H and He ions. The ion-beam-induced annealing has been studied as a function of ion dose and incident angle (channeling and random). Although the data sets differ markedly, they nearly coincide when the dose is normalized to the energy deposited by elastic collisions in the damaged region. This may indicate that nuclear and not electronic collisions contribute primarily to the in situ annealing in a reasonably good insulator such as diamond.

The use of band-edge reflection spectroscopy (BRS) to determine the substrate temperature during MBE is reviewed. Data are presented for Si, GaAs, InP and CdZnTe substrates, and the use of BRS during the growth of ZnTe on Si is demonstrated. We discuss complications that arise due to optical interference in the epitaxial layers, and methods to compensate for the effects of interference are described.

Structure and properties of diamondlike carbon films produced by pulsed laser deposition