Time-of-Flight secondary ion mass spectrometry (TOF-SIMS) using the metal-cluster-complex primary ion of Ir4(CO)7+

An orthogonal acceleration Time-of-Flight Secondary Ion Mass Spectrometer (TOF-SIMS) system has been developed with a metal-cluster-complex ion source. The ion source can produce ion beams of massive molecules called metal-cluster-complexes such as Ir-4(CO)(12), which has a molecular weight higher than 1000 u. Using the system, TOF-SIMS of a contaminated silicon substrate and a room temperature molten salt (i.e. an ionic liquid) was performed. The ionic liquid N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide, which has a molecularweight of 426 u, consists of a polyatomic cation, [C8H20ON](+), and a polyatomic anion, [C2F6NO4S2](-). During SIMS analysis, an analytical sample was bombarded with a continuous primary ion beam of either Ir-4(CO)(7)(+) or Ar+ in a beam energy of 10 keV at an incident angle of 45 degrees. It was confirmed that the use of Ir-4(CO)(7)(+) ions enhanced secondary ion intensity compared with that of Ar+ ions. Also, experimental results showed that the bombardment of Ir-4(CO)(7)(+) caused less fragmentation. In the case of the ionic liquid, cation-attached ionic-liquidmolecules were observed in addition to the cation of the ionic liquid. Copyright (C) 2010 John Wiley & Sons, Ltd.