Irradiation-induced improvement in crystal quality of epitaxial Ag∕Si(111) films

It has been found that 0.5MeV Si+ irradiation at −150°C greatly improves the crystal quality of epitaxially grown Ag films on Si(111) substrates. The improvements include the decrease in the population of twinning grains and the decrease in mosaic spread in the films. To clarify the mechanism of the irradiation-induced improvement in crystal quality (IIICQ), polycrystalline Ag films with [111] preferred orientation were also irradiated at −150°C. Grain growth in a lateral direction was clearly observed in such Ag films using x-ray diffraction (XRD) analysis. It is evident that the atomic rearrangements occur at grain boundaries due to low-temperature irradiation. On irradiation with 0.5MeV Si ions at −150°C the cross section for the grain growth, estimated by XRD analysis, is about 1.8×10−16cm2, very close to that achieved with IIICQ (1.9×10−16cm2) estimated by Rutherford backscattering spectroscopy/channeling analysis. This result indicates that the mechanism of the IIICQ for the epitaxial Ag∕Si(111) films is very similar to that of the ion bombardment enhanced grain growth.