Growth and stability of Pt germanides on Ge and GeSn substrates

In the pursuit of high-quality contact materials for (opto)electronic devices, replacing Ni with Pt is explored to offer a path towards more stable (stano)germanide contacts. In this study, we resolve the complex sequence of Pt (stano)germanide phase formation through real-time probing of the elemental redistribution using Rutherford backscattering spectrometry, complemented with X-ray diffraction, and the use of artificial neural networks. The existence of the Pt${}_3$(Ge(Sn))${}_2$ phase is confirmed, forming simultaneously with PtGe(Sn). Both Pt/Ge and Pt/GeSn systems follow the same phase sequence; however, the Pt/Ge system exhibits superior thermal stability of the monogermanide and the Ge-rich phases throughout an extended temperature range, as well as better morphological stability up to 600 °C, attributed to nucleation-controlled growth of the Ge-rich phases. The metastable incorporation of 7.5% Sn in Ge modifies the thermodynamic and kinetic behavior of Pt stanogermanide formation, as observed by the reduced compositional and morphological stability at elevated temperatures.