Graphene-Assisted Growth of Nanoblocks of Single-Crystalline Epitaxial Nickel Disilicides on Si(001)

摘要

We report on the growth of self-organized Nickel Disilicide nanoblocks on heated Si(001) using graphene-covered Nickel targets and e-beam evaporation. Room temperature evaporation results in the formation of {111} textured polycrystalline nickel films with negligible roughness as nickel cannot penetrate the native oxide of Silicon, which covers the Si(001) wafers. When the substrate temperature raises to 300℃ the native oxide of Silicon cannot act any more as a diffusion barrier and polycrystalline NiSi is formed. Growth at 800℃ results in a bimodal growth mode with the formation of single-crystalline NiSi_2 with <001> and <110> facets. On the other hand, if pure Nickel is used as a target, irregularly shaped NiSi_2 crystals are formed and the material is polycrystalline. Thus, the formation of single-crystalline epitaxial nanoblocks is attributed to the surfactant activity of Carbon originating from the graphene on the top of the Ni target. The best uniform monomodal growth mode of NiSi_2 is observed when the substrate temperature is maintained at 600℃, which is below the recrystallization temperature of the compound. The Silicon surface covered by epitaxial NiSi_2 nanoblocks may be promising for new applications in nanotechnologies.