Modifying Surface Energy of Graphene via Plasma-Based Chemical Functionalization to Tune Thermal and Electrical Transport at Metal Interfaces.

The high mobility exhibited by both supported and suspended graphene, as well as its large in-plane thermal conductivity, has generated much excitement across a variety of applications. As exciting as these properties are, one of the principal issues inhibiting the development of graphene technologies pertains to difficulties in engineering high-quality metal contacts on graphene. As device dimensions decrease, the thermal and electrical resistance at the metal/graphene interface plays a dominant role in degrading overall performance.

Protein Thermal Conductivity Measured in the Solid State Reveals Anharmonic Interactions of Vibrations in a Fractal Structure.

Energy processes and vibrations in biological macromolecules such as proteins ultimately dictate biological, chemical, and physical functions in living materials. These energetic vibrations in the ribbon-like motifs of proteins interact on self-similar structures and fractal-like objects over a range of length scales of the protein (a few angstroms to the size of the protein itself, a few nanometers). In fact, the fractal geometries of protein molecules create a complex network of vibrations; therefore, proteins represent an ideal material system to study the underlying mechanisms driving vibrational thermal transport in a dense, fractal network.

Crossover from incoherent to coherent phonon scattering in epitaxial oxide superlattices.

Elementary particles such as electrons or photons are frequent subjects of wave-nature-driven investigations, unlike collective excitations such as phonons. The demonstration of wave-particle crossover, in terms of macroscopic properties, is crucial to the understanding and application of the wave behaviour of matter. We present an unambiguous demonstration of the theoretically predicted crossover from diffuse (particle-like) to specular (wave-like) phonon scattering in epitaxial oxide superlattices, manifested by a minimum in lattice thermal conductivity as a function of interface density.

Exceptionally low thermal conductivities of films of the fullerene derivative PCBM.

We report on the thermal conductivities of microcrystalline [6,6]-phenyl C(61)-butyric acid methyl ester (PCBM) thin films from 135 to 387 K as measured by time domain thermoreflectance. Thermal conductivities are independent of temperature above 180 K and less than 0.030 ± 0.

Experimental investigation of size effects on the thermal conductivity of silicon-germanium alloy thin films.

We experimentally investigate the role of size effects and boundary scattering on the thermal conductivity of silicon-germanium alloys. The thermal conductivities of a series of epitaxially grown Si(1-x)Ge(x) thin films with varying thicknesses and compositions were measured with time-domain thermoreflectance. The resulting conductivities are found to be 3 to 5 times less than bulk values and vary strongly with film thickness.

Manipulating thermal conductance at metal-graphene contacts via chemical functionalization.

Graphene-based devices have garnered tremendous attention due to the unique physical properties arising from this purely two-dimensional carbon sheet leading to tremendous efficiency in the transport of thermal carriers (i.e., phonons).

Reducing thermal conductivity of binary alloys below the alloy limit via chemical ordering.

Substitutional solid solutions that exist in both ordered and disordered states will exhibit markedly different physical properties depending on their exact crystallographic configuration. Many random substitutional solid solutions (alloys) will display a tendency to order given the appropriate kinetic and thermodynamic conditions. Such order-disorder transitions will result in major crystallographic reconfigurations, where the atomic basis, symmetry, and periodicity of the alloy change dramatically.

Assessment and prediction of thermal transport at solid-self-assembled monolayer junctions.

Self-assembled monolayers (SAMs) have recently garnered much interest due to their unique electrical, chemical, and thermal properties. Several studies have focused on thermal transport across solid-SAM junctions, demonstrating that interface conductance is largely insensitive to changes in SAM length. In the present study, we have investigated the vibrational spectra of alkanedithiol-based SAMs as a function of the number of methylene groups forming the molecular backbone via Hartree-Fock methods.