Energy Dissipation and Transport in Nanoscale Devices

Understanding energy dissipation and transport in nanoscale structures is of great importance for the design of energy-efficient circuits and energy-conversion systems. This is also a rich domain for fundamental discoveries at the intersection of electron, lattice (phonon), and optical (photon) interactions. This review presents recent progress in understanding and manipulation of energy dissipation and transport in nanoscale solid-state structures. First, the landscape of power usage from nanoscale transistors (~10^-8 W) to massive data centers (~10^9 W) is surveyed. Then, focus is given to energy dissipation in nanoscale circuits, silicon transistors, carbon nanostructures, and semiconductor nanowires. Concepts of steady-state and transient thermal transport are also reviewed in the context of nanoscale devices with sub-nanosecond switching times. Finally, recent directions regarding energy transport are reviewed, including electrical and thermal conductivity of nanostructures, thermal rectification, and the role of ubiquitous material interfaces

Mobility and Saturation Velocity in Graphene on SiO2

We examine mobility and saturation velocity in graphene on SiO2 above room temperature (300-500 K) and at high fields (~1 V/um). Data are analyzed with practical models including gated carriers, thermal generation, "puddle" charge, and Joule heating. Both mobility and saturation velocity decrease with rising temperature above 300 K, and with rising carrier density above 2x10^12 cm^-2. Saturation velocity is >3x10^7 cm/s at low carrier density, and remains greater than in Si up to 1.2x10^13 cm^-2. Transport appears primarily limited by the SiO2 substrate, but results suggest intrinsic graphene saturation velocity could be more than twice that observed here

Electrical power dissipation in carbon nanotubes on single crystal quartz and amorphous SiO2

Heat dissipation in electrically biased semiconducting carbon nanotubes (CNTs) on single crystal quartz and amorphous SiO2 is examined with temperature profiles obtained by spatially resolved Raman spectroscopy. Despite the differences in phonon velocities, thermal conductivity and van der Waals interactions with CNTs, on average, heat dissipation into single crystal quartz and amorphous SiO2 is found to be similar. Large temperature gradients and local hot spots often observed underscore the complexity of CNT temperature profiles and may be accountable for the similarities observed

INFLUENCE OF EXPERIMENTAL CONDITIONS ON MATERIAL RESPONSE DURING THIXOEXTRUSION PROCESS

The behavior of aluminum alloy to deformation is strongly influenced by the morphology of the microstructure. This paper illustrates several experimental research activities for thixoextrusion of 7075 aluminum alloy being carried out within the “Arts et Métiers ParisTech” of METZ. Inductive re-heating of the aluminum billet is the method to enable the desired liquid fraction for thixoextrusion. Experimental results show that after induction reheating the solid particles obtained has globular shape and homogeneous dimension. A sample obtained from a direct extruded bar is inserted in a die and thixoextruded after reheating in semisolid state. In laboratory experiments the temperature it was directly controlled applying thermocouples for temperature measurements in the slug and also in the die. The experimental tests were made for two different working speeds on the mechanical eccentric press. The preliminary experimental results on extrusion load and microstructure evolution of the product are reported. These results will contribute to implementing the specific boundary condition of the manufacturing process to the future numerical analysis of the current project activities