In order to develop a new compact cluster ion source as a low damage sputtering source for SIMS to analyze ultra-shallow dopant state we have studied the possibility of using a metal cluster complex as an ion beam source. Metal cluster complexes such as Os-3(CO)(12) and Ir-4(CO)(12) have been studied from the view point of their stability in high vacuum and how to ionize them by using the electron ionization QMS and the XeCl laser ionization TOE In the case of electron ionization QMS, peaks of Os-3(CO)(n)(+)(n = 0-12) and lr(4)(CO)(n)(+) (n = 0-12) were observed without the fragment ions such as a monomer, a dimer, etc. In the case of laser ionization TOF, peaks of the fragment and the parent ions without a carbonyl ligand were observed from Os-3(CO)(12), and Ir-4(CO)(12). The temperature dependence of fragmentation has also been discussed. (C) 2004 Elsevier B.V. All rights reserved.