Structure and atoms mixing in electrodeposited Sn(Au) nanoaggregates

The tin (Sn) electrochemical deposition on insulating substrates has been performed to elaborate a distribution of supported nanoaggregates for gas sensors applications. Depending on current density, the deposit has either the shape of dendrites or of a homogeneous, continuous layer, thinner than 20 nm. In this study, fine current densities variation has been investigated to determine growth evolution, especially in the case of an additional transient layer of Au (vapor deposited). The deposits' morphology and structure have been examined by grazing incidence X-ray diffraction (GIXD), in correlation with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) coupled with selected-area electron diffraction (SAED). Analysis of the electrochemical deposits shows systematically the formation of a SnAu alloy with clusters diameter in the range 8-20 nm, whereas Sn particles are observed only under certain conditions. The SnAu alloy nanometer-sized particles are single crystals, generated by quick and spontaneous mixing of Sn and Au at room temperature (such a behavior is very slow in bulk materials). The annealing of these deposits at 300 °C leads to the formation of SnO and SnO2 active material.