Effect of Au on the crystallization of germanium thin films by electron-beam evaporation

Abstract

Metal induced crystallization is a widely used method to form crystalline/polycrystalline structures at low temperatures. In this work, Au was applied to enhance the crystallization of amorphous Ge films. Ge films with thicknesses of ∼1.5μm were fabricated by electron beam evaporation on c-Si substrate with and without very thin Au layer. Crystallization properties of Ge films were analyzed for different growth and post annealing temperatures varied between 270°C and 730°C. The structures of polycrystalline Ge films were investigated by employing X-ray diffraction (XRD), Raman spectra and scanning electron microscopy (SEM).The existence of thin Au layer showed significant impact on the crystallization of amorphous Ge films in terms of reducing the crystallization temperature. In post annealing processes, it was noticed that the impact of Au thin layer on crystallization slightly reduces above the temperature of ∼400°C, and almost no remarkable differences were observed between the films with and without Au layer in this temperature region. It is observed that the growth temperature has a stronger effect on the crystallization than post annealing temperatures in the presence of Au thin film. It is also shown that Au layer catalyzes the axial growth in the presence of planar Ge layer on the substrate surface.