Implications for SiGeSn growth from the surface science of Sn on Si

SiGeSn alloys are promising for optoelectronic applications due to their potential for simpler integration into silicon semiconductor manufacturing. However, a theoretically predicted direct bandgap has not been definitively observed experimentally, likely due to short-range ordering in the lattice. To understand this phenomenon, we used scanning tunneling microscopy (STM) to analyze the growth and annealing of sub-monolayer Sn on Si(100) substrates. Our data reveal that Sn forms 2x1 dimer chains on Si, but with reduced packing density due to steric repulsion. After annealing, Sn assembles into islands and incorporates into the topmost Si layer, exhibiting a 3x2 periodicity. The appearance of structures above the atomic scale is influenced by Sn coverage, annealing time, and temperature, while long-range periodicity is dictated by global strain. By comparing experimental data to modeling predictions, we aim to elucidate the driving forces behind short-range ordering in SiGeSn alloys and their implications for optoelectronic properties.