Matrix assisted laser desorption/ionisation studies of metallic nanoclusters produced by pulsed laser deposition

Abstract

Matrix assisted laser desorption/ionisation (MALDI) mass spectrometry has been used to study the formation of metallic nanoclusters by pulsed laser deposition (PLD). Cu nanoclusters were deposited by ablating a Cu target, both in Ar and vacuum. MALDI analysis leads to well defined peaks corresponding to masses in the range 400-500 amu and therefore to clusters of 6-8 Cu atoms, the presence of an Ar pressure during deposition having no significant influence on the size of the clusters. High resolution electron transmission microscopy observation of similar specimens shows the presence of clusters of thousands of amu (diameters of 1.5 nm to 4 nm). The discrepancies between the two techniques are discussed in terms of both their applicability ranges and the differences in the quality of the surface of the substrates used to apply each technique. © 1998 Elsevier Science B.V.