|Multiphysics modeling of the electromagnetic-coherent transport problem in nanodevices|
We introduce full-wave techniques both in the frequency (energy)-domain and the time-domain for the investigation of new devices based on carbon materials, namely carbon nanotubes (CNT), graphene, and graphene nanoribbons (GNR). The quantum transport is described by the Schrödinger equation or its Dirac-like counterpart, for small energies. The electromagnetic field provides sources terms for the quantum transport equations, that, in turn, provide charges and currents for the electromagnetic field. In the frequency-domain, a rigorous Poisson-coherent transport equation system is provided, including electrostatic sources (bias potentials). Interesting results involve new concept-devices, such as GNR nano-transistors and multipath/multilayer GNR circuits, where charges are ballistically scattered among different ports under external electrostatic control. Further examples are given by the simulation of cold-cathodes for field emission based on graphene and by the analysis of optical emission/absorption by single or few layer GNR. In the time-domain, we introduce a full-wave approach, in which the Maxwell equations, discretized by the transmission line matrix (TLM) method are self-consistently coupled to the Schrödinger/Dirac equations, discretized by a proper finite-difference time-domain scheme. We show several examples of the electromagnetics/transport dynamics in realistic environments. It is highlighted that the self-generated electromagnetic field may affect the dynamics (group velocity, kinetic energy etc.) of the quantum transport. This is particularly important in the analysis of time transients and in the describing the behavior of high energy carrier bands, as well as the onset of non-linear phenomena due to impinging external electromagnetic fields. We are now working on THz carbon-based emitters/detectors, CNT-enabled traveling wave (TW-CNT) devices, GaN HEMT and the carbon-metal transition; we are exploiting novel properties and devices based on frequency multiplication, graphene gyrotropic effects, Bloch oscillation, photoconductive effects.
|Laboratory Microscopy Lab at DII|
|Contact Person: Luca Pierantoni|