Defect analysis of epitaxial Ag films on silicon by MeV ion channeling

Abstract

The defect density of 2500 Å thick Ag films grown on Si(111) and Si(100) substrates by molecular beam epitaxy have been studied using MeV ion channeling and Rutherford backscattering spectrometry (RBS). Ion channeling measurements indicate that despite the large lattice mismatch between Ag and Si (~ 25%), the Ag films showed excellent epitaxy (χ min = 6–20%). In the best cases, the minimum yield was close to that expected for a perfect Ag crystal. Dechanneling was observed due to defects, predominantly dislocations which were distributed throughout the Ag film. Near the Ag/Si interface, the dislocation density was an order of magnitude higher than that found for the bulk of the Ag(111) film and produced an interface peak in the channeling spectra. These results show that high quality epitaxy can be achieved for even large mismatched heteroepitaxial systems such as Ag on Si and illustrate the power of the ion channeling technique for studying defects in crystalline films.