High-Speed Reflection Electron Microscopy of Laser-Induced Surface Transitions

Abstract

Micropatterning of bulk material by pulsed laser radiation is a promising technique for many applications, e.g. drilling and data storage. Due to the fact that laser radiation can be applied very localized, high power densities in a small volume of the treated specimen can be realized. As a result of rapid heat-up and cool-down processes, unusual phases and microstructures can be generated.Time-resolving methods, especially imaging with short exposures times are quite useful in order to understand the physics standing behind. As a diagnostic tool electrons are superior to other probes, e.g. light optics, due to their sensitivity to topography, material composition and structure. Unfortunately , the SEM - one of the most common microscopes for surface analysis - cannot be used for investigations in the the nanoseconds time domain due to its far to slow scan time. On the other hand, the reflection electron microscope (REM) is one of the very few instruments, which is capable to image all points of the treated surface simultanously.In order to achieve electron optical images of laser pulse induced processes on surfaces with exposures times of a few nanoseconds, a high-speed REM was developed. This new instrument is based on a conventional TEM, additionally equipped with the following units:- a laser pulsed thermal electron gun, which delivers high-brightness electron pulses with duration of 20ns.