Nanocluster formation by spin coating: Quantitative atomic force microscopy and Rutherford backscattering spectrometry analysis

Abstract

A recently developed spin coating method has been employed to produce a homogeneous distribution of nanometer-sized metal clusters onto a flat oxidic support. The particle size and distribution, and the total amount of material deposited has been studied by comparing the results of atomic force microscopy (AFM), Rutherford backscattering spectroscopy (RBS), and the appropriate hydrodynamic deposition equations. It is shown that the AFM is capable of producing a three-dimensional image of the surface which enables the particle number density and particle heights to be accurately determined. However, it is clear that as a result of tip convolution effects the particle diameter cannot be accurately determined. Using a hemispherical particle model the amount of material deposited during spin coating can be calculated from the AFM images. This calculation is shown to be accurate to approximately 50% in comparison with the results obtained from RBS. In contrast, it is shown that for a copper acetate precursor the predictions of the hydrodynamic equations are accurate to 2%. In the light of these results an assessment is made of the utility of AFM in the investigation of model catalyst systems and fundamental metal cluster studies.