Effects of Gas Ion Density on Formation of Gas-Atom Encapsulated Silicon Fullerenes

Silicon (Si) cage clusters, i.e., Si fullerenes doped with argon (Ar) atom are formed using a Si plasma. The Si plasma is generated by irradiation of an electron beam to a Si lump in Ar gas atmosphere. When the Ar gas pressure is 0.08 Pa or more, the Ar plasma is also generated by the collision of the electron beam and superimposed upon the Si plasma. The ionized Si agglutinates in the diffusion process and agglutinated Si fullerenes are deposited on a substrate. The mass analysis of the Si fullerenes deposited on the substrate is performed using a laser-desorption time-of-flight mass spectrometer. As a result, the mass peaks of the Si fullerenes doped with the Ar atom, i.e., Ar encapsulated Si fullerenes are observed only under the condition that the Ar ions are generated in addition to the Si plasma. This result suggests that the Ar ions influence the formation of the Ar encapsulated Si fullerenes.