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.

We report domain formation and spin phase transition in annealing induced self-assembled Ni nanodots on GaN with size distribution greater than the exchange length. The as-deposited Ni film shows stripelike magnetic domains. The enclosed spin well phase occurs due to annealed induced structural transition in the films. The reorientation occurs only at the center of the island. We also observed the magnetic correlation length remains constant during the structural phase change despite spin reorientation. The magnetic correlation length is destroyed for well-formed nanodots.

We report slow correlated growth mode in energetic cluster vapor deposited organic light emissive material tris(8-hydroxyquinoline) aluminum from 5 to 100 nm. Phase modulated atomic force microscopy shows very slow grain growth with thickness, with very small phase differences within the film. Fractal dimension calculated from correlation function shows growth process above 10 nm consistent with diffusion-limited aggregation. For low thickness (5 nm), photoluminescence measurement shows the emission peak is shifted by ∼0.4 eV toward lower wavelength.

Self-assembled interfaces in nanoscale structure made of metal; oxides and mixed composites have drawn a lot of attention due to its application in from photonics to sensor application. Here we report that for low melting point metals like aluminum, can self-assembly into well separated nanodots even with very high thickness (<150nm) when interface in driven close to their melting point. When electrochemical oxidized the stress causes discrete cross plastic slip without continuous deformation and forms stepped porous oxide nanostructure. The process is a very efficient way to make large-scale oxide or composite nanostructure for wide variety of application ranging from efficient solar cell to photonic devices.

We report the formation of hollow oxide nanostructures by oxidation of aluminum nanodots on gold thin film. The nanodots are formed by rapid thermal annealing of the thin film close to its melting point. The heights of the dots can be easily controlled via the initial thickness and temperature. The structure exhibits a phase transition when electrochemically oxidized and forms porous structure with a stepped interior. Despite the high level of disorder, a correlation length can be easily identified from the Fourier transformation of the surface. UV-visible spectroscopy and Fourier transform infrared spectroscopy show a stop gap at 1800 cm(-1) showing the potential for photonic material application despite the high level of disorder.

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.

We report the study on oscillatory pattern/domain formation due to energetic solid-state reaction in a metallic multilayer thin film using a scanning probe microscope. The observed oscillatory patterns become more ordered as the total thickness changed from 50nmto1.2μm. At higher thickness, a nonlinear cross oscillation pattern is also observed, which we attribute to spinning wave. The observed oscillation is modeled in terms of perturbation in the thermal wave. Magnetization measurement shows increased coercivity for the reacted film.

Roughening process in polydimethyl siloxane (PDMS) using atomic force microscopy is being studied using scaling law. As solidified PDMS showed surface undulation that is attributed to Grinfeld type instability. When the surface is annealed at 125 °C, a negative growth exponent is obtained. The growth exponent for annealing at 175 °C case was also found to be consistent with the diffusion driven model. However, the surface treated at this temperature does not exhibit any correlation length. For this particular type of solidification process, rougher surfaces led to larger growth exponent.

Anneal induced faceting of platinum (Pt) thin film is being studied by atomic force microscopy. We find that at 700 °C faceting occurs by first forming percolation clusters. The nanodots form low index facets with the substrate and with various geometric shapes parallel to the substrate. Time dependent coarsening kinetics shows Lifsitz-Slyozov/Wagner type diffusion therefore indicating Oswald ripening. Low index faceting of Pt nanodots is also stepped/faceted showing its potential application for efficient fuel cells.

Fungal colonies exhibit complex growth patterns depending on the environment. We report the formation of magnetic domains within fungal cells due to the growth of colonies in iron sulfate solution. We find that the initial growth of these colonies on silicon can be described by a roughness exponent of similar to 0.55 while annealed induced self-assembly has a roughness exponent of similar to 0.80. The growth mode is consistent with a quenched growth model. We also find high temperature (>600 degrees C) annealing induced colony parts to form oriented nanostructures with higher saturation magnetization. Using atomic force microscopy we show evidence of thermally induced capillary waves on island surfaces with a van der Waals cutoff wavevector of the order of 10(-2) angstrom(-1).

Evolution of surface structure during the annealing of e-beam evaporated Ti films is studied by means of atomic force microscopy (AFM). Image variography and power spectral density analysis are used to study scaling properties of the films, ranging from 50nm to 20μm length scale. No particular grain size is observed up to 473K. At 673K, grain size of ∼250nm are formed and coalesced to form bigger grain size upon further annealing. At 473K, RMS roughness dropped at all length scale and became rougher at 673K with an increasing trend up to 873K. Clustering at 673K indicates Kosterlitz–Thaouless [J.M. Kosterlitz, D.J. Thaouless, J. Phys. Chem. 6 (1973) 1181] type phase transition at the surface. The observed transition is also consistent with existing scaling laws.

We report studies of the formation of aluminum structures, with nanometer length scales, in ultrathin layers deposited on glass and analyzed using atomic force microscopy. Surface roughness, lateral cutoff length, and surface scaling exponent are all found to vary systematically with Al thickness. The initial nanocrystal formation is described by stress-energy minimization. We interpret the observed scaling behavior based on the kinetic theory of roughening. For very thin layers (<50nm) the roughness is consistent with a ∇4h growth factor, where h is surface height. For thick layers (>50nm) the ∇2(∇h)2 conserved mechanism is dominant. Substrate stress is not found to influence the scaling exponent through the kinetic theory.

We have studied interface of bubbles formed inside polydimethylsiloxane, a kind of biocompatible elastomer. Atomic force microscopy (AFM) and x-ray diffraction (XRD) were used to study the interface and structure. We have performed scaling analysis on two randomly picked bubbles of different diameters. These values show how the interface of bubble roughens at different scales. XRD studies show a definite bubble induced phase transition from crystal-like state to glasslike state. As the interface grows, one would expect that the interface would become smoother but we observed rougher interface. Roughness at macroscale is attributed to the oscillatory surface with wavelength of ∼2μm. At nanoscale, 100nm2 area AFM scan shows surface ripples which we attribute to nanoscale stress and frozen thermal fluctuations.