Cluster Superlattice Membranes

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Cluster superlattice membranes are a new type of two dimensional (2D) material. Such a membrane consists of clusters positioned in a 2D hexagonal array with a lattice constant of 2-4 nm. The lattice of clusters is of atomic precision, but of larger than atomic scale, and thus a superlattice. The cluster superlattice is sandwiched between a single crystal 2D layer of atomic thickness and an embedding matrix of nm thickness, such that the matrix together with the clusters and the 2D layer forms a mechanically stable sheet which can have mm lateral extension. Its mechanical integrity enables the transfer from a host substrate to another substrate or its use as a freestanding membrane. The clusters are tunable in size from the single atom limit up to about 400 atoms. The objective of the proposed research with these new 2D materials is threefold. First, it is the goal to develop the making of such membranes in order to obtain materials in a large diversity. This will include the realization open membranes, such that the clusters can interact with the environment, e.g. for applications in electrocatalysis. Post growth of clusters and combining open membranes with new metallic films will broaden their application potential for nanomagnetic investigations. Realization of membranes with oxides as a host material will give access to optical as well as electrical transport properties, and enable heterogeneous catalysis at elevated temperatures. Second, the membrane properties will be thoroughly analyzed, namely their proposed impermeability and stability in harsh environments. Of specific interest is their high temperature behavior. Here, excellent resistance against sintering is predicted, including suppression of Smoluchowski ripening and inverse Ostwald ripening. Third, to demonstrate the potential of these cluster superlattice membrane in fundamental research, we will construct membranes of magnetic particles and analyze their magnetic interaction. The cavities of the membranes that host the clusters will be used as reactors for phase transformations in small particles that otherwise would not be possible. Open noble metal superlattice membranes in carbon and oxide matrix will be tested as catalysts in liquid and gaseous environments.