High thermoelectric performance of graphite nanofibers.

Graphite nanofibers (GNFs) have been demonstrated to be a promising material for hydrogen storage and heat management in electronic devices. Here, by means of first-principles and transport simulations, we show that GNFs can also be an excellent material for thermoelectric applications thanks to the interlayer weak van der Waals interaction that induces low thermal conductance and a step-like shape in the electronic transmission with mini-gaps, which are necessary ingredients to achieve high thermoelectric performance. This study unveils that the platelet form of GNFs in which graphite layers are perpendicular to the fiber axis can exhibit outstanding thermoelectric properties with a figure of merit ZT reaching 3.

Non-linear effects and thermoelectric efficiency of quantum dot-based single-electron transistors.

By means of advanced numerical simulation, the thermoelectric properties of a Si-quantum dot-based single-electron transistor operating in sequential tunneling regime are investigated in terms of figure of merit, efficiency and power. By taking into account the phonon-induced collisional broadening of energy levels in the quantum dot, both heat and electrical currents are computed in a voltage range beyond the linear response. Using our homemade code consisting in a 3D Poisson-Schrödinger solver and the resolution of the Master equation, the Seebeck coefficient at low bias voltage appears to be material independent and nearly independent on the level broadening, which makes this device promising for metrology applications as a nanoscale standard of Seebeck coefficient.

Optimizing the thermoelectric performance of graphene nano-ribbons without degrading the electronic properties.

The enhancement of thermoelectric figure of merit ZT requires to either increase the power factor or reduce the phonon conductance, or even both. In graphene, the high phonon thermal conductivity is the main factor limiting the thermoelectric conversion. The common strategy to enhance ZT is therefore to introduce phonon scatterers to suppress the phonon conductance while retaining high electrical conductance and Seebeck coefficient.

High thermoelectric performance in graphene nanoribbons by graphene/BN interface engineering.

The thermoelectric properties of in-plane heterostructures made of Graphene and hexagonal boron nitride (BN) have been investigated by means of atomistic simulation. The heterostructures consist in armchair graphene nanoribbons to the sides of which BN flakes are periodically attached. This arrangement generates a strong mismatch of phonon modes between the different sections of the ribbons, which leads to a very small phonon conductance, while the electron transmission is weakly affected.

Thermoelectric effects in graphene nanostructures.

The thermoelectric properties of graphene and graphene nanostructures have recently attracted significant attention from the physics and engineering communities. In fundamental physics, the analysis of Seebeck and Nernst effects is very useful in elucidating some details of the electronic band structure of graphene that cannot be probed by conductance measurements alone, due in particular to the ambipolar nature of this gapless material. For applications in thermoelectric energy conversion, graphene has two major disadvantages.

Numerical and experimental assessment of charge control in III-V nano-metal-oxide-semiconductor field-effect transistor.

III-V Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) with a gate stack based on high-kappa dielectric appears as an appealing solution to increase the performance of either microwave or logic circuits with low supply voltage (V(DD)). The main objective of this work is to provide a theoretical model of the gate charge control in III-V MOS capacitors (MOSCAPs) using the accurate self-consistent solution of 1D and 2D Poisson-Schrödinger equations. This study allows us to identify the major mechanisms which must be included to get theoretical calculations in good agreement with experiments.

Monte Carlo simulation of III-V material-based MOSFET for high frequency and ultra-low consumption applications.

High-mobility III-V heterostructures are emerging and very promising materials likely to fulfil high-speed and low-power specifications for ambient intelligent applications. The main objective of this work is to theoretically explore the potentialities of MOSFET based on III-V materials with low bandgap and high electron mobility. First, the charge control is studied in III-V MOS structures using a Schrödinger-Poisson solver.