Influence of phase transitions on surface segregation processes in indium-tin solid alloys

The paper presents new experimental data on the surface composition of In-Sn solid alloys over the entire range of volume concentrations. The surface segregation of components in In-Sn binary solid alloys has been studied by electron Auger spectroscopy. The alloys were prepared in an inert medium at 573 K with volume composition control by X-ray fluorescence spectroscopy. Before surface analysis, alloy samples were brought to an atomically pure state by irradiation with argon ions ( E = 700 eV, J = 1 µA/cm2) followed by annealing to achieve an equilibrium state. Auger peak amplitudes were measured under ultrahigh vacuum conditions (residual pressure 10-7 Pa) from room temperature to 443 K over the entire volume concentration range, including solid solutions, homogeneous and two-phase regions, as well as phase transitions. According to the Auger analysis performed for MNN transitions of In and Sn, the surface concentrations of the samples were calculated. The constructed isotherms of the surface composition showed that mutual segregation of the components is observed in the studied temperature range. Based on the obtained values of surface concentrations, the segregation energies of indium and tin in the region of solid solutions are calculated, confirming the surface activity of both components. It is established that the polytherms of the surface composition are approximated by linear equations with positive and negative temperature coefficients.

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