Thermal stability and transformation of C₆₀ molecules deposited on silicon-coated (111) iridium

Abstract

Thermal stability and transformation of C₆₀ molecules deposited onto a silicon film on (111) iridium have been studied in ultrahigh vacuum within the temperature range of 300–1900 K. The temperature range covered is shown to break up into four consecutive regions, each dominated by its own specific process; namely, thermal stability of C₆₀ films (T<600 K), desorption of fullerene molecules from the second and subsequent molecular layers (800–900 K), decomposition of these molecules in the first layer which contacts the substrate (650–850 K), graphitization of the carbon layer into a thermally stable two-dimensional graphite film (900–1700 K), and thermal desorption of carbon from the surface (T>1900 K). These processes retain their qualitative character as one passes from Si submonolayer films to (4–5)-monolayer-thick films.