Nature routinely produces nanostructured surfaces with useful properties, such as the self-cleaning lotus leaf, the colour of the butterfly wing, the photoreceptor in brittlestar and the anti-reflection observed in the moth eye. Scientists and engineers have been able to mimic some of these natural structures in the laboratory and in real-world applications. Here, we report a simple aperiodic array of silicon nanotips on a 6-inch wafer with a sub-wavelength structure that can suppress the reflection of light at a range of wavelengths from the ultraviolet, through the visible part of the spectrum, to the terahertz region. Reflection is suppressed for a wide range of angles of incidence and for both s- and p-polarized light. The antireflection properties of the silicon result from changes in the refractive index caused by variations in the height of the silicon nanotips, and can be simulated with models that have been used to explain the low reflection from moth eyes. The improved anti-reflection properties of the surfaces could have applications in renewable energy and electro-optical devices for the military.

The hydride transfer mechanism of the NAD model compound 1 to its 1,4-NADH derivative 3 [Eq. (1)] is proposed to be a consequence of the critical role of the carbonyl group of the amide to coordinate to the ring-slipped η - to η -Cp*Rh metal center of the catalyst [Cp*Rh(bpy)H] , prepared in situ from 2, while a steric effect of a substituent in the 3 position, for example, C(O)NEt , was found to totally inhibit this regioselective reduction. bpy=2,2'-bipyridine, Cp*=C Me , OTf=trifluoromethanesulfanate.

Well-aligned nanotip arrays were fabricated by electron cyclotron resonance (ECR) plasma process using gas mixtures of silane, methane, argon, and hydrogen. The resultant tips have nanoscale apexes (∼1 nm) with high aspect ratios (∼50), which were achieved by simultaneous SiC nanomask formation and dry etching during ECR plasma process. This technique was applied to a variety of substrates such as silicon, polycrystalline silicon, gallium nitride, gallium phosphide, sapphire, and aluminum, indicating its general applicability. High-resolution transmission electron microscopy and Auger depth profile analyses revealed that the SiC cap, with Si:C ratio of 1:1, exhibited 3C−SiC and 2H−SiC structure on Si and GaP, respectively, with heteroepitaxial relationship. This one-step self-masked dry etching technique enables the fabrication of uniform nanotip arrays on various substrates over large area at low process temperatures, thereby demonstrating a high potential for practical industrial application.