Magnetic Topology of Fe Nanostructure with Curvature on GaAs

Magnetic systems where long-range and short-range interactions can give rise to domains, like fractional vortex, domain walls, etc., are widely studied. While interacting artificial frustrated systems are studied for flat nanomagnet, curved surfaces are not accessible to modern lithographic techniques. We report self-assembly of dense Fe nanomagnet on GaAs with positive curvature. While domain formation is absent within the nanodots due to high interfacial stress, strong down-spin response is observed at the grain boundary. Using magnetic force microscopy, we report formation of “core-like” solitary defects with domain formation at the grain boundaries and junctions.     

Growth of GaN Nanowires on Epitaxial GaN

We report experiments on the formation of GaN nanowires on epitaxial GaN using thin layers of Ni. GaN covered with Ni shows roughening that is strongly dependent on the thickness of the Ni layer and the annealing conditions. With the initial Ni thickness of 0.8 nm we observe formation of Ni-filled antidots. These act as nucleation sites in the growth of GaN nanowires, allowing for the preparation of nanowires with an average diameter as small as 30 nm. Dense and well-oriented nanowires are formed by pulsed metallorganic chemical vapor deposition at 750°C. The size of the Ni features determines the diameter of the GaN nanowires, resulting in good control over the formation process.     

Antireflection displays with ambient contrast enhancement for extended device battery lifetime and reduced energy consumption

Antireflection (AR) coatings can improve the viewing experience of a display, including mobile electronic devices such as smartphones, tablets, and laptops that are typically operated on battery power and protected with chemically strengthened glass. In this work, we discuss the trade‐offs between optimal user viewing experience in brightly lit environments and battery lifetime for an AR versus a non‐AR mobile display. We show that under 400–1,000 lux ambient illumination, an AR‐based display can be operated at >30% lower luminance than a non‐AR display with similar human perception of contrast based on a perceptual contrast length model, resulting in a potential improvement of >15% in device battery lifetime and a similar proportion of energy savings.