Platinum thin films and particles on oxide surfaces are interesting for various applications in microelectronics and catalysis. Atomic layer deposition (ALD) of Pt from MeCpPtMe3 precursor and O2 gas has recently emerged as a promising technique to fabricate these structures on demanding topologies such as high-aspect ratio surfaces or porous catalyst supports. The surface reactions of Pt ALD are governed by dissociative chemisorption of O2 at the Pt surface, and catalytic combustion and dehydrogenation of the MeCpPtMe3 precursor ligands,1 which is limited during nucleation on oxides due to the absence of a catalytic surface. In this work, it is established that a parameter that has not been investigated so far, the O2 exposure (i.e. pressure × time) during the reactant half-reaction of the ALD cycle, plays a crucial role during the nucleation of Pt ALD. Under influence of the oxygen, deposited Pt atoms diffuse over the surface and form small islands, and these islands subsequently catalyze the surface reactions of Pt ALD. As a result, the nucleation delay for Pt growth decreases with increasing O2 exposure. It is shown that the particle ripening is absolutely essential for the Pt ALD growth to occur. For low O2 exposures, there is no growth at all on Al2O3 substrates. The O2 exposure can be used as a parameter to tune the nucleation behavior, and this has some important consequences for the applications. For example, the O2 exposure dependence can be exploited to minimize the nucleation delay for the deposition of ultrathin closed Pt films, to fabricate particles with a narrow size distribution for catalysis applications, or to obtain selective growth on seed layer patterns for nanopatterning applications.2

[1] A.J.M. Mackus, N. Leick, L. Baker, W.M.M. Kessels, Chem. Mater., (accepted for publication).

[2] A.J.M. Mackus, J.J.L. Mulders, M.C.M. van de Sanden, W.M.M. Kessels, , 116102 (2010)