We report results on the synthesis of silicon nanostructures that were fabricated using a combination of interference lithography and catalytic etching. With this technique, we were able to create nanostructures that are perfectly periodic over very large areas (1 cm(2) or more), where the cross-sectional shapes and the array ordering can be varied. Furthermore this technique can readily and independently control the sizes and spacings of the nanostructures down to spacings of 200 nm or less. These characteristics cannot be achieved using other known techniques.

The electroluminescent spectra and the light intensities of Alq3-based organic light-emitting diodes were measured as a function of the thickness of the light-emitting layer. A maximum in the light intensity occurs when the thickness of this layer is approximately 600 Å, whereas a minimum in the light intensity occurs at about 1400 Å. The electroluminescent spectra were also found to vary strongly with the thickness of the light-emitting layer. Computer simulation, based on wide-angle interference of light-emitting dipoles from a reflective mirror, can account for the experimental observations.

We have investigated Ti/Au ͑30/50 nm͒ ohmic contacts to n-ZnO:Al. The samples are annealed at temperatures of 300 and 500°C for 60 s in a flowing N 2 atmosphere. Current-voltage measurements show that the as-deposited sample is ohmic with a specific contact resistance of 2 ϫ 10 Ϫ2 ⍀ cm 2 . However, annealing of the sample at 300°C results in much better ohmic behavior with a contact resistance of 2 ϫ 10 Ϫ4 ⍀ cm 2 . Further increase in annealing temperature ͑500°C͒ causes the degradation of the ohmic property. Glancing angle X-ray diffraction and Auger electron spectroscopy are used to investigate interfacial reactions between the Ti/Au and ZnO layers. It is shown that both rutile and srilankite TiO 2 phases are formed in the as-deposited and annealed samples. It is further shown that annealing at 500°C results in the formation of new phases such as Ti 3 Au and TiAu 2 . A possible explanation is given to describe the annealing temperature dependence of the specific contact resistance.

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We describe a new method of fabricating large-area, highly scalable, "hybrid" superhydrophobic surfaces on silicon (Si) substrates with tunable, spatially selective adhesion behavior by controlling the morphologies of Si nanowire arrays. Gold (Au) nanoparticles were deposited on Si by glancing-angle deposition, followed by metal-assisted chemical etching of Si to form Si nanowire arrays. These surfaces were chemically modified and rendered hydrophobic by fluorosilane deposition. Au nanoparticles with different size distributions resulted in the synthesis of Si nanowires with very different morphologies (i.e., clumped and straight nanowire surfaces). The difference in nanowire morphology is attributed to capillary force-induced nanocohesion, which is due to the difference in nanowire porosity. The clumped nanowire surface demonstrated the lotus effect, and the straighter nanowires demonstrated the ability to pin water droplets while maintaining large contact angles (i.e., the petal effect). The high contact angles in both cases are explained by invoking the Cassie-Baxter wetting state. The high adhesion behavior of the straight nanowire surface may be explained by a combination of attractive van der Waals forces and capillary adhesion. We demonstrate the spatial patterning of both low- and high-adhesion superhydrophobicity on the same substrate by the simultaneous synthesis of clumped and straight silicon nanowires. The demonstration of hybrid superhydrophobic surfaces with spatially selective, tunable adhesion behavior on single substrates paves the way for future applications in microfluidic channels, substrates for biologically and chemically based analysis and detection where it is necessary to analyze a particular droplet in a defined location on a surface, and as a platform to study in situ chemical mixing and interfacial reactions of liquid pearls.