The usefulness of the usage of cluster primary ion source together with an Ag substrate and detection of Ag cationized molecular ions was studied from the standpoint to realize high sensitivity TOF-SIMS analysis of organic materials. Although secondary ions from polymer thin films on a Si substrate can be detected in a higher sensitivity with Au-3(+) cluster primary ion compared with Ga+ ion bombardment, it was clearly observed that the secondary ion intensities from samples on an Ag substrate showed quite a different tendency from that on Si. When monoatomic primary ions, e. g., Au+ and Ga+, were used for the measurement of the sample on an Ag substrate, [M+Ag](+) ions (M corresponds to polyethylene glycol molecule) were detected in a high sensitivity. On the contrary, when Au-3(+) was used, no intensity enhancement of [M+Ag](+) ions was observed. The acceleration energy dependence of the detected secondary ions implies the different ionization mechanisms on the different substrates. (C) 2008 Elsevier B. V. All rights reserved.