The effect of stress and kinetic reaction barriers on the reactive growth of nanometer-sized epitaxial NiSi2 islands on Si(111)

Growth kinetics and interface structures of epitaxial, nanometer-sized NiSi₂ islands of A- and B-orientations on Si(111) single-crystal substrates are studied by RBS, TEM/SAED, and high-resolution TEM on cross sections. The islands grow by an in situ solid state reaction between the silicon substrate and a nickel vapour at temperatures of 300°C and 400°C. Owing to a crossover of the thermal expansion curves of NiSi₂ and Si at 400°C, stresses determine the shares of (three-dimensional) A-islands and (two-dimensional) B-islands at different temperatures. Furthermore, A-islands contain dislocations, whereas B-islands are completely free from lattice defects, with the exception of interfacial steps of various heights occurring at the NiSi₂/Si(111) growth fronts of both island types. These steps play an essential role in the island growth. The difference in the reaction kinetics observed between A- and B-islands at 400°C is explained in terms of different kinetic reaction barriers present at the structurally different NiSi₂Si(111) growth fronts under the A-and B-islands