SIMULATION OF THERMIONIC EMISSION FROM A QUANTUM WIRE USING THE NON-EQUILIBRIUM GREEN'S FUNCTION METHOD

摘要

Even though the theory of thermionic emission of electrons from bulk metals is well understood, discrete electron energy states exist when material length scales approach one nanometer, and the traditional treatment must be revised. This paper presents a theoretical development of thermionic emission from nanoscale materials. A general expression for the emitted current as a function of field, temperature and work function is established for a quantum wire. The results differ from those of 3-D bulk materials. Simulation of thermionic emission from a quantum wire is achieved with the nonequilibrium Green's function (NEGF) method, which includes relevant mesoscopic physics and has been widely applied to transport problems in nanostructures. The NEGF approach provides a powerful solution to modeling problems when interfacial transport effects between bulk and confined conductors are important. Both the theoretical and simulated results indicate a higher current density and thus higher energy conversion capacity than that of a bulk material with the same work function. Thus the quantum confined materials may provide a method for improving the capacity of direct energy conversion devices and systems.