An exact quantum theory for photoemission from dielectric coated metal surfaces under a dc bias

• Published in: IEEE conference record-abstracts - IEEE International Conference on Plasma Science p. 1
• Main Authors: Zhou, Yang, Zhang, Peng
• Format: Conference Proceeding
• Language: English
• Published: IEEE 12.09.2021
• Subjects: Dielectrics; Free electron lasers; Mathematical models; Metals; Photoelectricity; Surface emitting lasers; X-ray lasers
• ISSN: 2576-7208
• DOI: 10.1109/ICOPS36761.2021.9588391

Photoelectron emission is important for many applications, such as free electron lasers (FELs), ultrashort X-ray sources, time-resolved electron microscopes, ultrafast electron diffraction, and novel nano-electronics [1] - [4] . For stable operation of cathodes, surface coatings are fabricated to protect them from degradation by ions and electrons bombardment and oxidization. There are also native oxides and adsorbates formed on the emitter surface under poor vacuum conditions. These coatings have a strong impact on electron emission. In this study, we construct an analytical quantum theory for photoemission from metal surfaces coated with an ultrathin dielectric under a dc bias, by exactly solving the one-dimensional (1D) time-dependent Schrödinger equation subject to a double-triangular potential barrier. The theory includes the effects of metal properties (i.e. work function and Fermi level), dielectric properties (i.e. thickness, relative permittivity, and electron affinity), laser field (i.e. strength and wavelength), and dc field. Our results show that the introduction of dielectric coating can induce resonance behavior, which is ascribed to the electron wave interference inside the dielectric. Our model is compared with the effective single-barrier quantum model [3] , [5] and modified Fowler-Nordheim equation [6] , for both 1D flat cathodes and pyramid-shaped plasmonic resonant nanoemitters. The latter with coating can emit photoemission current orders of magnitude higher than those without coating [6] . For the special case of zero laser field, an empirical relation between the threshold dielectric thickness and threshold dielectric relative permittivity is given for the condition under which the dc field emission current can be enhanced by adding a surface coating [4] . This work provides insights for designing cathodes of higher efficiency and better stability.