Length-dependent thermal conductivity in suspended single-layer graphene.

Graphene exhibits extraordinary electronic and mechanical properties, and extremely high thermal conductivity. Being a very stable atomically thick membrane that can be suspended between two leads, graphene provides a perfect test platform for studying thermal conductivity in two-dimensional systems, which is of primary importance for phonon transport in low-dimensional materials. Here we report experimental measurements and non-equilibrium molecular dynamics simulations of thermal conduction in suspended single-layer graphene as a function of both temperature and sample length.

Profiling nanowire thermal resistance with a spatial resolution of nanometers.

We report a new technique to profile the thermal resistance along a nanowire with a spatial resolution of better than 20 nm. Using this technique, we mapped the thermal conductivity along a Si0.7Ge0.

Diameter-dependent thermal transport in individual ZnO nanowires and its correlation with surface coating and defects.

A systematic study of the thermal transport properties of individual single-crystal zinc oxide (ZnO) nanowires (NWs) with diameters in the range of ∼50-210 nm is presented. The thermal conductivity of the NWs is found to be dramatically reduced by at least an order of magnitude compared to bulk values, due to enhanced phonon-boundary scattering with a reduction in sample size. While the conventional phonon transport model can qualitatively explain the temperature dependence, it fails to account for the diameter dependence.

Thermal transport in suspended and supported few-layer graphene.

We report thermal conductivity (κ) measurements from 77 to 350 K on both suspended and supported few-layer graphene using a thermal-bridge configuration. The room temperature value of κ is comparable to that of bulk graphite for the largest flake, but reduces significantly for smaller flakes. The presence of a substrate lowers the value of κ, but the effect diminishes for the thermal transport in the top layers away from the substrate.

Controllable epitaxial crystallization and reversible oriented patterning of two-dimensional colloidal crystals.

We demonstrate a reliable and highly efficient epitaxial templating approach for the formation of two-dimensional (2D) colloidal crystals. By applying an alternating electric field (AEF), one-dimensional colloidal lines are used as an epitaxial template to site specifically initiate 2D colloidal crystallization and control the orientation of the 2D colloidal crystals. The kinetics of the crystallization and structure ordering is precisely and conveniently manipulated by the external AEF.

Low-temperature growth of uniform ZnO particles with controllable ellipsoidal morphologies and characteristic luminescence patterns.

Uniform ellipsoidal ZnO particles have been synthesized in an aqueous solution in the presence of triethonalamine (TEA) mediated by sonication at the temperature below 80 degrees C. Scanning electron microscopy observations reveal that the ellipsoidal particles are highly uniform with a hexagonal cross-section. The morphologies of the ZnO particles can be systematically controlled from elongated rugby ball-like ellipsoidal to half-ellipsoidal by increasing the TEA concentration.

Precise fabrication of point defects in self-assembled three-dimensional macroporous photonic crystals.

We demonstrate a new and simple method of precisely fabricating defects in three-dimensional (3D) CdS macroporous photonic crystals (PCs) with a variable pressure scanning electron microscope. Well-defined point defects, not only vacancies but also an impurity (a reduced-size sphere), were directly fabricated by electron-beam irradiation under a gas atmosphere. This provides a convenient and straightforward method of introducing various designed defects into 3D PCs for photonic-band-gap-based applications.

Perfectly dissolved boron nitride nanotubes due to polymer wrapping.

We report for the first time that boron nitride nanotubes (BNNTs) may be dissolved in organic solvents by wrapping them with a polymer. Transmission electron microscopy and cathodoluminescence studies indicate the strong pi-pi interactions between BNNTs and the polymer. A band gap ranging from 5.