Formation of a rosette pattern in copper nitride thin films via nanocrystals gliding

By sputtering synthesis of cubic Cu(3)N, which decomposes at moderate temperatures, film growth proceeds with simultaneous nitrogen reemission from inside, leading to the formation of some unusual structures or morphology. We report a relief morphology comprising densely packed rosette-like features. The rosettes, typically 20 microm in size, show a radial furcation followed by successive bifurcation at approximately 74 degrees , resulting in a fivefold symmetric structure sometimes. The area expansion of the features can be as large as ten per cent with regard to the underlying bottom. Scanning electron micrographs reveal that it is the gliding of Cu(3)N nanocrystals along the Cu-rich {111}-planes that is responsible for the unusually large area expansion. The gliding and packing along the {111}-planes also explain the bifurcation angle of the ramified rosettes. Such a relief morphology can serve as a template for large-area fabrication of concave structures by inverse duplication, adding to the already abundant innovative applications of this material.