Terence Musho

Quantum simulation of thermionic emission from diamond films

Recent advances in wide-band gap thermionic materials have brought to question the applicability of well accepted theories for thermionic emission from metallic surfaces. The authors developed a nonequilibrium Greens function (NEGF) self-consistent model based on quantum mechanics to investigate thermionic emission from nitrogen-incorporated diamond cathodes. The model allows us to relax several assumptions typical of Richardsons equation. The NEGF method is a self-consistent Schrodinger–Poisson formalism where the transport is calculated from an effective mass description and Fermi-Dirac statistics. The predictions were validated against experimental measurements from nitrogen-incorporated diamond cathodes. The model captures key emission characteristics such as the onset temperature of emission and the emission from low or negative electron-affinity materials. The results indicate that Richardsons equation overestimates emission for many cases, especially in low electron affinity materials. In additi...

QUANTUM SIMULATION OF NANOCRYSTALLINE COMPOSITE THERMOELECTRIC PROPERTIES

The electrical transport properties of semiconductor nanocrystalline composite (NCC) thermoelectric structures were studied from a quantum point of view using a 2D non equilibrium Greens function (NEGF) computational approach. Previous researchers have shown enhancement in thermal properties of NCC devices but have not extensively studied their electrical transport properties for increased thermoelectric performance. The NCC structure was parameterized to determine the performance as a function of crystal spacing and crystal size. Results indicate that a silicon matrix (well) and a germanium crystal (barrier) configuration result in the highest Seebeck coefficient. Power factors of NCC devices were compared to equivalent superlattice devices, and greater performance was shown for equivalent NCC characteristic lengths.

NEGF Quantum Simulation of Field Emission Devices

Recent studies of wide band-gap diamond field emission devices have realized superior performance and lifetime. However, theoretical studies using standard Fowler-Nordheim (FN) theory do not fully capture the physics of diamond semiconductor emitters as a result of the fitting parameters inherent to the FN approximation. The following research computationally models wide band-gap field emission devices from a quantum point of view, using a novel non-equilibrium Green’s function (NEGF) approach previously applied to modeling solid-state electronic devices. Findings from this research confirm non-linearities in the FN curve and provide alternative explanations to discrepancies between standard FN theory.Copyright

Thermoelectric Power Factor Calculator for Nanocrystalline Composites

Quantum Simulation of the Seebeck Coefficient and Electrical Conductivity in a 2D Nanocrystalline Composite Structure using Non-Equilibrium Greens Functions