Studies on the reaction mechanism of si-CVD and mono-cluster synthesis

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Radicals or reaction intermediates containing Si atom play an important role in many CVD system and in the formation mechanism of silicon nano-clusters. Although existence of Si_2H_n radicals is demonstrating by quantum mechanical calculations, many important radicals such as disilane have not yet detected in the gas phase. We developed a new time-of flight mass spectrometer combined with a laser multi-photon ionization to detect these Si-containing radicals. Si-containing radicals were produced by the abstraction of H atom from SiH_4 or Si_2H_6 by Cl atom. Cl atom was generated by using two different method : ArF laser photolysis of C_2Cl_4 and the microwave discharge of Cl_2. In these reaction system, Cl, SiH,and SiH_3 could be detected by the resonantly-enhanced multi-photon ionization (REMPI). In addition, many ion signals signals form Si^+, SiH^+, SiH_2, Si_2, and Si_2Hn could be detected, but signal intensities of these ions are almost independent on the ionization wavelength. It is concluded these ions are produced by the non-resonant ionization of some parent molecules.Experiments to investigate the dimerization processes of SiH_3 radicals were also performed. H_2 and Si_2H_6 produced by the SiH_3+SiH_3 reaction were detected by Q-pole mass spectrometer with elctron-impact ionization. Branching ratio of the product channels was determined.