Synthesis of Au−C60 Cluster Materials

Abstract

We have investigated the formation of Au clusters in a C 60 fullerene matrix (binary cluster material) with the aim to produce densely packed arrays of ultrasmall Au clusters with sizes below 4 nm. We achieved the formation of a binary cluster material by co-deposition of Au and C 60 , and no segregation of the gold was observed. The Au concentration throughout the film was observed with Rutherford backscattering spectroscopy and reflects the deposition rates measured for the single particle fluxes. It was determined by high-resolution TEM that the films show a narrow size distribution of the Au clusters. The size ranges from 1.6 to about 3.8 nm, and the size distribution is determined by the Au concentration. For low Au concentrations of less than 5 atom %, the maximum of the size distribution was positioned at about 2 nm with a full width at half-maximum of 0.5 nm. The gold appears to have a strong influence on the growth mechanism of the films, as evidenced by a dramatic reduction in the mean roughness of the films with increasing Au content, which was observed with atomic force microscopy. For high gold concentrations, the surface roughness decreases to less than half the radius of a C 60 molecule. The competition between surface and volume cluster growth and the role of the Au cluster-fullerene interaction in the film growth are discussed.