SURFACE-PLASMON POLARITONS AND LIGHT EMITTING TUNNEL JUNCTIONS (PRISM, ATR)

Tunnel junctions have recently been shown to emit visible light. Such devices are called light emitting tunnel junctions (LETJ) and consist of two thin metal films separated by a very thin oxide layer. A LETJ structure is typically less than 1000 (ANGSTROM)ngstroms thick with an oxide barrier thickness of a few tens of (ANGSTROM)ngstroms. Applying a voltage bias between the two metals results in current flow across the oxide barrier due primarily to electron tunneling. Investigations of the LETJ have been directed toward the possibility of creating display devices.; Metal film interfaces, such as those of a LETJ, support several well defined surface electromagnetic modes, called surface-plasmon polaritons (SPP). The wavevector of a SPP in the plane of the interface is larger than that of free electromagnetic radiation. Such modes are bound to the interface by wavevector conservation, however, radiation may be accomplished by wavevector matching using a grating or prism.; Light emission from LETJs has been clearly related to radiative decay of SPPs and basically is a two-step process, with tunneling electrons exciting the SPP which in turn radiates though a coupling prism, for example. This dissertation is based upon applications of prism coupling techniques to the study of LETJs. A major advantage of the prism method over grating coupling is that it allows virtually exact calculations of light emission to be compared directly to experiment. In addition, the reflectivity of multilayer films can be calculated and compared with attenuated-total-reflection (ATR) experiments in order to determine film parameters (dielectric constants and film thicknesses.); Light emission through the prism has both angle and wavelength dependence. Results show that although light emission versus angle is well accounted for, the wavelength spectrum has a clear discrepancy with the theory. Arguments are presented to suggest that the two-step process must be amended to include SPP mode conversion.