Morphology studies of iron-manganese thin films

Fe-based catalysts are known to be effective for Fischer-Tropsch synthesis from coal but are sensitive to sulfur poisoning. Addition of manganese to these catalysts has been proposed in an effort to combat this catalyst deactivation. To investigate the fundamental physical aspects of Mn incorporation into Fe, different compositions of model thin films of Fe-Mn, ranging from 100% Fe to 100% Mn were studied for the very first time, using scanning tunneling microscopy (STM), atomic force microscopy (AFM) and scanning electron microscopy. Our preliminary results indicate that the grain size of iron varied from 50 nm to 150 nm using the AFM image, in general agreement with others. Also the mixture with small amounts of manganese had large oxidic area. The surface was modified by the addition of manganese. The STM images of the samples showed similarities between pure iron and 75% Fe- 25% Mn, while the 25% Fe-75% Mn looked very similar to 100% Mn. The mixture of 50% Fe-50% Mn seemed to contain two distinct surface features. This leads us to believe that STM and AFM can be useful tools to further investigate the model iron-manganese thin films and hence give insight into the un-known atomic scale interactions and also to study the catalytic properties better.