Topology-directed silicide formation: an explanation for the growth of C49-TiSi₂ on the Si(100) surface

Designing metal-semiconductor (MS) junctions is essential for optimizing the performance of modern nanoelectronic devices. A widely used material is TiSi₂, which combines low electronic resistivity with good endurance. However, its multitude of polymorphs poses a challenge for device fabrication. Although the low-resistivity C54-TiSi₂ is thermodynamically favored, silicide formation on Si(100) nucleates through the metastable C49-TiSi₂ phase, whose unfavorable electronic properties limit device performance. The origin of this phase selection remains poorly understood despite the ubiquity of TiSi₂ in nanoelectronic devices. Based on extensive density functional theory calculations, we present a comprehensive model of Ti adsorption on Si(100) that highlights the pivotal role of surface topology for the initial stages of the interfacial TiSi₂ formation process. We show that the interplay between Si surface dimers, the symmetry of the Si(100) surface, and the incorporation of Ti adsorbates below the surface drives an adsorption pattern that yields a nucleation template for the C49-TiSi₂ phase. This novel perspective on the unique growth of TiSi₂ will not only pave the way for next-generation electronic devices, but also demonstrates how silicon's surface topology can be a decisive factor for optimizing MS-junctions at the nanoscale.