Deposition of Ge_1-xC_x alloy on Si by combined low-energy ion beam and molecular beam epitaxial method

A combined ion beam and molecular beam epitaxial method was applied for the formation of a Ge_1-xC_x alloy on Si(100) using a low-energy (50-100 eV) C⁺ ion beam and a Ge molecular beam. Ge_1-xC_x alloys were formed up to x = 0.047. It was revealed that the sticking coefficients of C⁺ ions into Ge were approximately 53% and approximately 34% at the ion energies of 100 eV and 50 eV, respectively. This result suggests that the ratio of the number of ions recoiling at the surface of the substrate to the number of incident ions is higher for lower energy ions within the ion energy range examined. Characterization of crystal structure by X-ray diffraction suggests that the deposited films are single crystals grown epitaxially on the substrate with twins on {111} planes. Study of the C-1s chemical shift by X-ray photoelectron spectrometry in the sample of x = 0.047 revealed that the total composition of C atoms incorporated in substitutional and interstitial lattice sites is about 72%, while that of C atoms incorporated in the form of precipitate is about 28%. Lattice dynamical characterization by Raman spectroscopy suggests that the deposited layers have been damaged by ion irradiation.