CoSi ultrathin films on Si(111) substrate: comparison of the stage formation in ultra-high vacuum and during annealing in argon

As a result of the study, optimal conditions were identified for the formation of ultrathin films of cobalt monosilicide (CoSi) on a silicon substrate during a single annealing (T = 500–600 °C) of chromium layers (2–10 nm), both under ultra-high vacuum conditions and in an argon environment during isochronous annealing. The formation of the phase composition in ultrathin CoSi films is uniquely controlled in situ during growth in ultrahigh vacuum by the appearance of a bulk plasma frequency peak at 20.2–20.3 eV in the EELS spectrum, a Raman peak at 198 (204) cm^-1 in ex situ Raman studies of the annealing in an argon environment (in vacuum) and characteristic of CoSi optical functions of refractive index and extinction and optical phonons at 223.7, 302.5 and 418.6 cm^-1. It has been established that cobalt films not subjected to thermal annealing in a vacuum begin to oxidize when annealed in an argon  environment, which is convenient to monitor by the appearance of Raman peaks at 187 cm^-1 and 670-677 cm^-1.