Seminars Archive

Secondary Electron Emission: From the Fundamental Mechanisms to Spectro-Microscopy with Nanometre Resolutions

Abstract
In spite of more than a century of research on the phenomenon of secondary electron emission from solid surfaces, the underlying mechanisms involved in their generation and ejection still need to be fully clarified. Since the typical energy loss in a solid corresponds to the mean energy of the solid-state electrons, the first step towards thermalisation always involves the creation and emission of low-energy secondary electrons, independently from the primary energy and from the type of the impacting particle. Nowadays, due to the broad variety of applications for these low-energy secondaries, there is a great interest in controlling this phenomenon, which in turn requires the understanding of the elementary physical processes leading to their emission. This work reports on the recent developments in the field of electron-induced secondary electron emission studied in the low-energy regime (for kinetic energies 100 eV). The interaction of low-energy electrons with surfaces exhibiting different long-range order, was investigated by means of spectroscopic tools of increasing finesse: combining measurements of the total electron yield in absolute units, single- electron as well as (e,2e)-coincidence spectroscopy. This investigation has led to an improved understanding on the elementary processes involved in the secondary electron generation probability, fully taking into account both energy and momentum conservation in the collision, many-body effects – i.e. plasmons – as well as the band structure of the solid. Furthermore, an attempt at interpreting the signal generation and contrast mechanism relevant in electron-based imaging techniques such as in Scanning Field-Emission Microscopy will be presented.