Electronic conduction and superconducting properties of CoSi_2 films on silicon–an unconventional superconductor with technological potential

We report observations of unusual normal-state electronic conduction properties and superconducting characteristics of high-quality CoSi_2/Si films grown on silicon Si(100) and Si(111) substrates. A good understanding of these features shall help to address the underlying physics of the unconventional pairing symmetry recently observed in transparent CoSi_2/TiSi_2 heterojunctions [S. P. Chiu et al., Sci. Adv. 7, eabg6569 (2021); Nanoscale 15, 9179 (2023)], where CoSi_2/Si is a superconductor with a superconducting transition temperature T_c ≃ (1.1–1.5) K, dependent on its dimensions, and TiSi_2 is a normal metal. In CoSi_2/Si films, we find a pronounced positive magnetoresistance caused by the weak-antilocalization effect, indicating a strong Rashba spin-orbit coupling (SOC). This SOC generates two-component superconductivity in CoSi_2/TiSi_2 heterojunctions. The CoSi_2/Si films are stable under ambient conditions and have ultralow 1/f noise. Moreover, they can be patterned via the standard lithography techniques, which might be of considerable practical value for future scalable superconducting and quantum device fabrication.