Identification of fragment ions produced by the decomposition of tetramethyltin and the production of low-energy Sn + ion beam

摘要

Tetramethyltin was decomposed in an ion source and the fragment ions produced were identified using a low-energy mass-selected ion beam machine. Dominant fragment ions were found to be H + , CH 2 + , and Sn + . Subsequently, fragment ions were mass-selected. The mass spectrum of the selected ions indicated that only a single peak appeared at the mass number of 120 u, being suggestive of the presence of 120 Sn + ions. The ion energy was set at the range of 20–100 eV. The Sn + ion beam was irradiated to a Si substrate, and a film was then found deposited on the substrate after the ion beam irradiation. An X-ray diffraction measurement showed that the film obtained was metallic Sn. Then, the Sn + ion beam was irradiated to a quartz crystal microbalance substrate. We found that most of the irradiated Sn + ions were adhered to the substrate, at the ion energy levels of 25 and 58 eV, producing the Sn film, whereas a 107 eV Sn + beam caused a significant proportion of Sn atoms in the film to detach from the substrate, probably due to sputtering.