Atomic scale of ruthenium silicidation and diffusion behaviors by in-situ transmission electron microscope investigation

Transition metal silicides possess high thermal stability and good electrical conductivity, making them widely used in various engineering fields. Ruthenium silicide, a narrow-bandgap semiconductor, combines low chemical reactivity with a high thermoelectric figure of merit, making it promising for optoelectronic and thermoelectric devices. Solid-state reaction provides a straightforward route to synthesize high-quality ruthenium silicide. To elucidate the formation mechanism, in-situ transmission electron microscopy (TEM) was employed to directly monitor the silicidation and diffusion processes. The silicidation initiates with crystallization of the amorphous Ru layer into a polycrystalline structure at 210 °C. Between 300 °C and 500 °C, Si diffusion into the Ru layer leads to the formation of RuSi and Ru2Si via a diffusion-controlled mechanism. At 700 °C, Ru2Si3 forms through either diffusion-controlled or nucleation-controlled pathways. Through atomic-scale observation, this study provides the first comprehensive understanding of the silicidation behaviors and dynamic diffusion process of ruthenium, offering a complete reaction mechanism.