The secondary electron emission phenomenon often refers to the emission of electrons as a result of the interaction of impinging energetic electrons with the surface of a material. Although it is fairly well described for metals, with a typical shape of the total electron emission yield (TEEY) first increasing to reach a maximum and then decreasing along with the energy increase of the primary electrons, there is still a lack of data and detailed analysis for dielectrics, in particular thin layers. The present work proposes a new insight in the electron emission phenomenon from very thin dielectric layers. It reports on the TEEY from very thin SiO2 layers, less than 100 nm. It is found that a departure from the typical shape of the TEEY curve occurs for primary electrons with energy of around 1 keV. The TEEY curve presents a dip, a local minimum that might be as deep as below 1. This atypical shape depends substantially on the layer thickness. The measured TEEY are compared to an electron emission 1D-model in which we consider the combined effect of the space-charge electric field induced by trapped charges in the dielectric layer and of the processes of field dependent conductivity (FDC) and radiation induced conductivity (RIC) on the fate of secondary electrons. Those mechanisms govern the charge transport in the dielectric, and consequently the electron emission. The effects of the SiO2 layer thickness, incidence angle of the primary electrons and an applied external electric field on the TEEY curves are reported.
The secondary electron emission phenomenon lays down the principle of operation of many physical devices and processes. Although it is fairly well described in the case of irradiation of metals there is still lack of information on the secondary electron emission when originating from dielectrics. In this work we report on the secondary electron emission resulting from very thin layers. It is found that for dielectric SiO 2 layers of less than 100 nm of thickness a departure from the general behaviour occurs for incident primary electrons with energy of around 1 keV. The departure in the electron emission yield heavily depends on the layer thickness. The case of nanostructured layersdielectric matrices containing metal nanoparticles is also considered in the study.
The electron emission yield of materials is an important quantity to be determined in various fields of physics. Among them, dielectric materials have a strong ability to retain charges and remain charged when submitted to electrical field, in particular when irradiated by electron beam. Without the use of specific measurement methodology, experimental investigation of dielectric materials may lead to an inaccurate measurement of the total electron emission yield (TEEY). This paper shows that a particular attention should be paid to the pulse duration of the incident electron beam and to hysteresis effects induced by charge trapping.
The electron emission yield of materials is an important quantity to be determined in various fields of physics. Among them, dielectric materials have a strong ability to retain charges and remain charged when submitted to electrical field, in particular when irradiated by electron beam. Without the use of specific measurement methodology, experimental investigation of dielectric materials may lead to an inaccurate measurement of the total electron emission yield (TEEY). This paper shows that a particular attention should be paid to the pulse duration of the incident electron beam and to hysteresis effects induced by charge trapping.
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