Determination of stoichiometry in silicon carbide materials using elastic backscattering spectrometry

Elastic backscattering spectrometry (EBS) was performed on SiC materials, using ⁴He particles at energies ranging from 2 to 4 MeV, in order to establish the energy values that lead to an accurate measurement of the Si/C ratio. Analysis of the random yield of “bulk” SiC single crystals indicates that energy values of 3.25 and 3.75 MeV are the most suitable for chemical composition determination; backscattering yield of carbon is enhanced compared to the yield measured at 2 MeV, while the excitation of strong resonances above 3.75 MeV are suppressed. Random backscattering yield measurements were then carried out at an energy of 3.25 MeV on unhydrogenated SiC thin films grown on Si(1 0 0), by pulsed laser deposition, at different substrate temperatures. The Si and C atomic concentrations in the films were determined with an uncertainty of 1% and little interference from the underlying substrate. The films were found to be stoichiometric with a Si/C ratio of 1.03 ± 0.05, independent of deposition temperature, which indicates that the films were grown under congruent ablation conditions. The analysis proved to be applicable to both amorphous and crystalline SiC layers, as confirmed by the results obtained for films deposited at 400 and 950 °C, respectively.