We investigated the magnetotransport of InAs nanowires grown by selective-area metal-organic vapor phase epitaxy. In the temperature range between 0.5 and 30 K reproducible fluctuations in the conductance upon variation in the magnetic field or the backgate voltage are observed, which are attributed to electron interference effects in small disordered conductors. From the correlation field of the magnetoconductance fluctuations the phase-coherence length l is determined. At the lowest temperatures l is found to be at least 300 nm while for temperatures exceeding 2 K a monotonous decrease in l with temperature is observed. A direct observation of the weak antilocalization effect indicating the presence of spin-orbit coupling is masked by the strong magnetoconductance fluctuations. However, by averaging the magnetoconductance over a range of gate voltages a clear peak in the magnetoconductance due to the weak antilocalization effect was resolved. By comparison of the experimental data to simulations based on a recursive two-dimensional Green's-function approach a spin-orbit scattering length of approximately 70 nm was extracted, indicating the presence of strong spin-orbit coupling.

The electrical transport property of the reduced graphene oxide (rGO) thin-films synthesized from defective GO through thermal treatment in a reactive ethanol environment at high temperature above 1000 °C shows a band-like transport with small thermal activation energy (Ea~10 meV) that occurs during high carrier mobility (~210 cm2/Vs). Electrical and structural analysis using X-ray absorption fine structure, the valence band photo-electron, Raman spectra and transmission electron microscopy indicate that a high temperature process above 1000 °C in the ethanol environment leads to an extraordinary expansion of the conjugated π-electron system in rGO due to the efficient restoration of the graphitic structure. We reveal that Ea decreases with the increasing density of states near the Fermi level due to the expansion of the conjugated π-electron system in the rGO. This means that Ea corresponds to the energy gap between the top of the valence band and the bottom of the conduction band. The origin of the band-like transport can be explained by the carriers, which are more easily excited into the conduction band due to the decreasing energy gap with the expansion of the conjugated π-electron system in the rGO.

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We report on the selective area metal–organic vapour phase epitaxial growth of an InGaAs nano-pillar array on a partially masked InP(111)B substrate. This technique is very promising as a way to form semiconductor two-dimensional photonic crystals (2DPCs) suitable for infrared optical fibre communication. We successfully formed uniform hexagonal 2DPCs having vertical (110) facet sidewalls on 400 nm-pitch masked substrates. We observed vertical growth enhancement as well as the lateral overgrowth suppression for high aspect ratio InGaAs nano-pillar array formation under high growth-rate, long growth-time, and narrow window-opening conditions. We verified infrared emission from the InGaAs nano-pillar array by low-temperature photoluminescence measurement.

Multilayer graphene was synthesized by overlayer growth of graphene on a monolayer graphene template using a chemical vapor deposition method under a high process temperature of 1300 °C. Structural analysis using Raman spectra revealed that the synthesized multilayer graphene forms highly crystalline graphene layers with a turbostratic stacking structure. Atomic force microscope images indicated that the step edges of the grown graphene layer proceed via lateral growth mode. The electrical transport properties of the synthesized multilayer graphene showed higher conductivity and carrier mobility than those of the monolayer graphene template. The improvement of the electrical transport properties is caused by the turbostratic stacking structure that has the electronic band dispersion similar to that of monolayer graphene. This result means that the synthesis of graphene layers grown on the graphene template is effective to improve the carrier transport properties in multilayer graphene sheets.

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The thickness and aspect ratio dependence of magnetic domain formation in CoFe nanolayer patterns on GaAs (001) substrates are investigated by means of a direct approach using magnetic force microscopy at room temperature. Magnetic force microscope observations under as‐deposition condition show that magnetic domain formation in the patterns depends strongly on the aspect ratio and thickness of the patterns and the crystallographic orientations of the substrates. A single magnetic domain is more easily formed in the patterns with a higher aspect ratio, with a thinner nanolayer thickness, and along the ⟨110⟩ direction of the substrates. The magnetic fields are next applied in the direction parallel to the ⟨1–10⟩ and ⟨110⟩ orientations of the substrates to characterize a magnetization switching behavior in the patterns. The aspect ratio and thickness of the patterns and the crystallographic orientations of the substrates strongly affect the magnetic fields needed for magnetization switching in the patterns. A higher magnetic field is required for a higher aspect ratio and a thinner nanolayer thickness of the patterns. All the direct observations confirm that the magnetic domain structures and magnetization switching are tuned by controlling aspect ratio and thickness of the patterns and the crystallographic orientations of the substrates.