Surface Reaction of Silicon Clustere and Molecular Dynamics Simulations of Nucleation of Silicon Thin Film

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Employing the Fourier Transform Ion-Cyclotron Resonance (FT-ICR) mass spectrometer with direct-injection cluster beam source, chemical reaction of silicon clusters with 10-30 atoms to ethylene and nitric oxides was studied. For the reaction studies of Si clusters with ethylene, the laser annealing effect and the reactivity for wide cluster size range were obtained. During the reaction experiments with NO, the abstraction of Si atom expressed as Si_n^+ + NO → Si_<n-1>N^+ + SiO was observed. Furthermore, it was demonstrated that the daughter clusters with certain number of Si atoms dissociated into small pieces after this reaction.In addition, chemical reaction experiments of carbon-metal binary clusters and metal clusters such as Fe, Co and Ni were also investigated in conjunction with the formation mechanism of single-walled carbon nanotubes.By the molecular dynamics simulations using the Tersoff potential model, crystallization process of silicon from amorphous or liquid was studied. Small seed crystal structure was embedded in an amorphous or liquid cluster with 4000-8000 atoms. Depending on the temperature of the system, the growth or decay of the crystal structure was simulated. The growth rate of the crystal and the critical nucleation size were compared with the classical nucleation theory. It was found that the obtained crystals usually had several twin defects. By visualizing each single-crystal part of clusters, the formation of twin defects was investigated. It was demonstrated that twin defects were formed when the crystal grew with (111) surface. In addition, several interesting structures such as the pseudo-crystal with 5-fold symmetry were obtained.