Effect of the interface structure on the high-temperature morphology of supported metal clusters

Imaging the real shape of nanoclusters in scanning force microscopy

“…We performed dynamic SFM measurements on palladium nanoclusters grown on MgO͑001͒ because it is an important model catalyst 1 and because it has a well-known geometry. 32,33 We achieved a good agreement between experiment and theory, which shows that the contrast can be indeed explained by the short-range interaction between the tip and cluster. By a more general analysis, we explain that the high-resolution constant height imaging of nanoclusters can be basically achieved as long as the last nanometer of the tip is physically or chemically sharp.…”

“…The main characteristic of the constant height image are the expected rectangular shapes of the clusters and the expected 45°orientation of the nanoclusters with respect to the ͗001͘ step of the MgO͑001͒ surface. 32 A comparison of the cluster sizes in many of such constant height images with those of large clusters found in TEM images on the same sample surface shows a quantitative agreement.…”

“…3͔. 32,33 An important characteristic is also the angle of 45°between the edges of the nanoclusters and ͗001͘ steps of the MgO͑001͒ surface. 1,32 Prior to TEM imaging, the same surface was imaged with the force microscope at room temperature after the deposition of Pd.…”

“…44 The Pd clusters were modeled in their expected shape of a truncated octahedron with an angle of 54.73°between the ͑001͒ top facet and the ͑111͒ side facets, and with a ratio of 0.45 between the cluster height and cluster base length. 32,33 The height and lateral size information was taken from the experimental topography and constant height images. Although it might be that the height of the nanometer-sized clusters is not well represented in dynamic SFM images, 25 we nevertheless used the cluster height values from our experimental images as guide values.…”

Equilibrium shapes and triple line energy of epitaxial gold nanocrystals supported onTiO2(110)

“…At the interface, this could happen for example by nucleation of dislocations at larger NC sizes ͑for example, Pd NCs on MgO͒. 33 By imaging the interfacial atomic structure with atomic resolution STEM, we found that atomic structure of interfaces was similar for all NC sizes and we did not observe misfit dislocations at the interface. No obvious surface reconstruction was detected in our experimental images.…”