Multiscale Simulations of High Performance Capacitors and Nanoelectronic Devices

Recent advances in theoretical methods combined with the advent of massively-parallel supercomputers allow one to reliably simulate the properties of complex materials and device structures from first principles. We describe applications in two general areas: (i) novel polymer composites for ultrahigh density capacitors, necessary for pulsed power applications, such as electric rail guns, power conditioning, and dense electronic circuitry, and (ii) ballistic electron transport in novel molecule-on-semiconductor structures exhibiting negative differential resistance. The phase diagram of P(VDF-CTFE), which has an usually high energy density, is determined as a function of the electric field. The calculations explain the origin of the observed ultra-high capacitance and suggest a systematic route, not limited to polymers, for obtaining nanostructured materials with high energy density. Turning to molecular electronics, we investigated porphyrins between Si leads, which are candidates for molecular memories and logic. We show that they exhibit tunable negative differential resistance (NDR). In some cases, huge peak-to-valley ratios are obtained, which should result in excellent switching behavior.