Wirelike growth of self-assembled hafnium silicides: oxide mediated epitaxy

A wirelike shape of Hf silicides, which is not observed in silicides directly grown on Si (0 0 1), has been obtained by oxide mediated epitaxy (OME). Hafnium deposition (∼0.4 and ∼0.2 ML) onto ultrathin (∼1 nm) SiO2 and annealing at 900°C resulted in the formation of self-assembled wirelike silicides via a silicate phase (Hf-O-Si bonding units) in the 600-800°C temperature range. Silicide nanowires were found to be encapsulated in the bundle aggregates. The number density of OME-grown silicides apparently decreased as a form of nanowire bundles along with an increasing aspect ratio compared with the directly grown disilicides on Si (0 0 1). This finding has an implication for the use of an ultrathin SiO2 layer in controlling the tradeoff between the number density and the aspect ratio of self-assembled silicides.