Important aspects of investigating optical excitations in semiconductors using a scanning transmission electron microscope

Abstract

Since semiconductor structures are becoming smaller and smaller, the examination methods must also take this development into account. Optical methods have long reached their limits here, but small dimensions are also a challenge for electron beam techniques, especially when it comes to determining optical properties. In this paper, electron microscopic methods of investigating optical properties are discussed. Special attention is given to the physical limits and how to deal with them. We will cover electron energy loss spectrometry as well as cathodoluminescence spectrometry. We pay special attention to inelastic delocalisation, radiation damage, the Čerenkov effect, interference effects of optical excitations and higher diffraction orders on a grating analyser for the cathodoluminescence signal.