We experimentally investigate the mechanism of formation of self-assembled arrays of nanoislands surrounding dopant sources on the (001) surface of yttria-stabilized zirconia. Initially, we used lithographically defined thin-film patches of gadolinia-doped ceria (GDC) as dopant sources. During annealing at approximately one-half the melting temperature of zirconia, surface diffusion of dopants leads to the breakup of the surface around the source, creating arrays of epitaxial nanoislands with a characteristic size (~100 nm) and alignment along elastically compliant directions, <110>. The breakup relieves elastic strain energy at the expense of increasing surface energy. On the basis of understanding the mechanism of island formation, we introduce a simple and versatile powder-based doping process for spontaneous surface patterning. The new process bypasses lithography and conventional vapor-source doping, opening the door to spontaneous surface patterning of functional ceramics and other refractory materials. In addition to using GDC solid-solution powders, we demonstrate the effectiveness of the process in another system based on Eu2O3.
We have combined self-assembled ceramic nanoislands with nanoimprinting to demonstrate a novel, simple, low-cost method for polymer surface patterning. The nanoislands are easy to make and inexpensive, and can produce different distinct island morphologies. With a similar stiffness to steel, the nanoislands have superior durability to silicon, glass, polydimethylsiloxane (PDMS), and other common nanoimprinting materials. The nanoislands are stable up to 1000 degrees C and resist acids, bases, and solvents. We have demonstrated nanoimprinting with PDMS, ethyleneglycol dimethacrylate, and polystyrene polymers. The combination of desirable properties, ease of making, and low cost suggests a useful nanopatterning platform for a wide array of research fields.
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