Metal Nano Clusters (Ag and Au on graphite)

Metal nano clusters are used in a variety of application, such as catalysis, bio-sensors, medicine, electronics and optics. All these applications require a stable array of clusters to be formed. As an example, in catalysis Au clusters can catalyze the oxidation of carbon monoxide and Ag clusters the oxidation of ethylene. A combination of both of these clusters in a single system could lead to parallel or sequential catalytic processes on a single surface.

Many metals have catalytic properties, hence the work is aimed at the development of new cluster applications.

This investigation is an example of AES analysis focused on finding the distribution of Au and Ag nano clusters on a graphite surface. It was expected that the Au and Ag clusters would be intermixed across the whole of the sample surface, but this was not the case. Analysis showed there to be distinct regions of Ag clusters, separated from regions of Au clusters. This is demonstrated in the SEM image and Ag Auger electron map shown below where every particle observed in the SEM is shown to be Ag in the map.

SEM image of sample and surface and Ag map of the same area

On the sample there were large and small Ag clusters (50 nm down to 5 nm). Similar Auger maps of Au clusters were found in adjacent regions.

Survey spectrum from Au cluster and Au Auger map

The Au clusters appeared to be more sparsely distributed than the Ag clusters.

Many nano cluster catalytic and biological interactions are cluster size specific, hence this work helped the client to adjust the production process to give the required size distribution and efficient intermixing of Au and Ag clusters.

The particular study illustrates the advantages of Auger electron spectroscopy in the elemental composition of very small features on sample surfaces.

Other areas where the technique is uniquely valuable is in failure analysis of semiconductor device structures, where the analysis of nano-scale features is required.

For further information, please contact info@midsurfanalysis.co.uk or telephone +44 (0)121 204 3530 or alternatively please complete our analysis request form and a consultant will be in contact.