The group IV semiconductors such as silicon (Si) and germanium (Ge) are unique materials with a wide range of technological applications. A versatile integrated device for the semiconductor industry is highly desirable for advanced applications. Notwithstanding the widespread application of Ge its use is not as extensive as that of Si, and nebulous domains in our understanding of its precise technical functions still remain. Previous nanostructures have either been one-dimensional nanomaterials such as nanowires, nanorods, nanobelts/nanoribbons, nanotubes, two-dimensional nanoscale thin films, or zero-dimensional nanoparticles, which all have integer dimensions. Herein, the non-integer dimensional Ge nanostructures, referred to as nanofractals, were successfully assembled by high-vacuum thermal evaporation techniques. We have found that the thermodynamically driven assemblies of Ge nanocrystals possess amazing nanostructures such as polycondensation-type Ge nanofractals with non-integer dimensions, thick branches and smooth edges, metastable gamma-Au0.6Ge0.4 nanocrystals, and a variety of interesting micro/nanometer-sized features. The results of computer simulations using a ripening mechanism of non-uniform grains agree very well with the patterns formed in experiments.

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DOI: 10.1016/S1369-7021(11)70060-8