Microstructure and optoelectronic properties of Au, Sn, Au-Sn thin films near the percolation threshold

Abstract

The nanolayers of gold, tin, and gold-tin alloy of nominal thickness 2.5 nm, 5.0 nm and 10.0 nm have been deposited using the thermal evaporation method on the silicon substrate. The surface topography of the produced thin films was carefully studied by means of the atomic force microscopy technique, composition was investigated using the x-ray photoelectron spectroscopy and their optical properties were examined using the spectroscopic ellipsometry method. All of the produced films exhibit nanogranular structure. The surface topography and optical properties of the layers strongly depend on the thickness and the deposition rate. The thin films of AuSn alloys are composed of Au, Sn and AuSn grains, wherein the layer composition becomes more and more uniform for the thickest one.