B. Q. Li

Surface evolution of ultrahigh vacuum magnetron sputter deposited amorphous SiO2 thin films

The surface morphology evolution of amorphous SiO2 thin films deposited by ultrahigh vacuum radio-frequency magnetron sputtering was studied by atomic force microscopy. The results show that: (1) the surface roughness of the deposited films reduces with increased substrate temperatures; (2) the surface roughness increases with higher deposition pressures; and (3) there is a roughening transition at the critical thickness of ∼ 90 nm for the substrate temperature of 713 K. The results also show that the surface roughness at the early stages of growth evolves according to a power law. Further growth beyond the critical thickness leads to a sharp increase in roughness. The experimental results are compared with the previous theoretical and experimental studies on surface evolution during sputter deposition, and discussed in terms of the competition between surface diffusion and shadowing.

Self-assembly of epitaxial Ag nanoclusters on H-terminated Si(111) surfaces

We report an experimental investigation on self-assembly of epitaxial Ag nanoclusters on H-terminated Si(111) surfaces. We show that epitaxial Ag clusters of 2–6 nm in diameter can be synthesized by depositing at room temperature, followed by in situ annealing. As-deposited Ag clusters are uniformly distributed on the surface with a well-defined minimum spacing. The Ag clusters are mostly single crystals with Ag(111)//Si(111). The in-plane orientation of the as-grown clusters has a dispersion of ∼9° centering around the Si[110] direction. Upon annealing, most Ag clusters rotate to the epitaxial orientation with Ag[110]//Si[110]. The nanocluster rotation and epitaxy are explained using the coincident site lattice model for the interface structure and interfacial energy minimization.

Nanocluster interfaces and epitaxy: Ag on Si surfaces

We summarize our experimental investigation of the morphology and orientation of Ag nanoclusters on silicon surfaces formed by room-temperature (RT) deposition and subsequent annealing. Using Ag as a model system, we showthat nanocluster interfaces and epitaxy depend critically on the cluster size and the substrate lattice. In case of Ag on hydrogen-terminated Si (111), the RT self-assembled clusters grow as mostly single-crystal crystallites with Ag (111)//Si (111), but the in-plane orientation has a dispersion of ∼ 9° centering at Si [110] direction. Upon annealing, the Ag clusters drastically rotated to the epitaxial configuration with the in-plane orientation aligned to the Ag[110]//Si[110] direction. The rotation and epitaxy of the Ag nanoclusters are explained based on a coincident site lattice model and interface energy minimization.

Nanocluster Epitaxy by Annealing: Ag on H-terminated Si (111) Surfaces

We report an experimental investigation on the morphology and orientation of Ag nanoclusters by RT deposition and subsequent annealing. We show that epitaxial Ag clusters of 2 ∼ 6 nm in diameter can be synthesized in this way. The RT self-assembled Ag clusters grow as mostly single-crystal crystallites with Ag(111)//Si(111), but the in-plane orientation has a dispersion of ∼ 9° centering at Si[110] direction. Upon annealing, the Ag clusters drastically rotated to the epitaxial configuration with the in-plane orientation aligned to the Ag[110] //Si[110] direction. The rotation and epitaxy of the Ag nanoclusters are explained based on a coincident site lattice model and interface energy minimization.