In the optimization of multilayer stacks for various optical filtering purposes not only the thicknesses of the thin films are to be optimized, but also the sequence of materials. Materials with very different optical properties, such as metals and dielectrics, may be combined. A genetic algorithm is introduced to search for the optimal sequence of materials along with their optical thicknesses. This procedure is applied to a heat mirror in combination with a blackbody absorber for thermal solar energy applications at elevated temperatures (250 °C). The heat mirror is based on silver films with antireflective dielectric layers. Seven dielectrics have been considered. For a five-layer stack the sequence (TiO(2)/Ag/TiO(2)/Ag/Y(2)O(3)) is found to be optimal.

The tungsten tip of a scanning tunneling microscope, covered with GeHx by exposure to GeH4, was used to locally grow nanometer-sized Ge or GeHx islands on a Si(111)-(7×7) surface. This was achieved by transfer of material from the tip to the surface, induced by voltage pulses. A model, based on the diffusion of adsorbates on the tip and desorption stimulated by an electric field, is presented to account for the results.

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