The effect of the deposition rate on morphology, opto-electronic properties and formation intermetallic compounds of Au–Sn alloys

Microstructure and opto-electronic properties of thin films strongly depend on the deposition conditions. The 50 nm gold-tin alloy (Au-50%at.Sn and Au-67%at.Sn) layers were prepared using the physical vapour deposition technique. The tin and gold layers were deposited on the SiO2 - coated Si substrates in two systems Au∖Sn and Sn∖Au at four different deposition rates in the range from 0.05 Å/s up to 2.50 Å/s. The influence of the deposition rate on the sample morphology was investigated using atomic force microscope and X-ray diffraction. Changes in the microstructure of the Au–Sn layers cause variations in their opto-electronic properties. These features were examined using spectroscopic ellipsometry measurements. We found that Au-50%at.Sn alloy layers exhibit significantly lower values of optical resistivity than those obtained for Au-67%at.Sn alloy films, whereas the lowest value (29 μΩcm) was obtained for Au-50%at.Sn deposited at 0.15 Å/s and 0.50 Å/s. •The Au–Sn alloys were formed using thermal evaporation.•Microstructure of Au–Sn solders strongly depend on sequence of Au and Sn layers.•Microstructure of Au–Sn alloy depend on the deposition rate of Au and Sn films.•The films with Sn deposited on Au demonstrate more uniform structure.•The lowest value of the optical resistivity is equal to 29 μΩcm.