NANOCLUSTER FORMATION BY SPIN-COATING - QUANTITATIVE ATOMIC-FORCE MICROSCOPY AND RUTHERFORD BACKSCATTERING SPECTROMETRY ANALYSIS

A recently developed spin coating method has been employed to produce a homogeneous distribution of nanometer-sized metal clusters onto a fl at oxidic support. The particle size and distribution, and the total a mount of material deposited has been studied by comparing the results of atomic force microscopy (AFM), Rutherford backscattering spectrosco py (RES), 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 re sult of tip convolution effects the particle diameter cannot be accura tely determined. Using a hemispherical particle model the amount of ma terial deposited during spin coating can be calculated from the AFM im ages. This calculation is shown to be accurate to approximately 50% in comparison with the results obtained from RES. In contrast, it is sho wn that for a copper acetate precursor the predictions of the hydrodyn amic equations are accurate to 2%. In the light of these results an as sessment-is made of the utility of AFM in the investigation of model c atalyst systems and fundamental metal cluster studies. (C) 1996 Americ an Vacuum Society.