Time-resolved thermal-emission electron microscopy of laser-pulsed metal surfaces

Abstract

A time-resolving thermal-emission electron microscope was developed for tracking transient phenomena on pulse-laser-heated metal surfaces. Short-time exposures with a temporal/spatial resolution of 3 ns/1 μm were achieved by adding a high-gain image intensifier and a fast beam blanking unit to a conventional emission microscope. Fast surface heating was realized using a frequency-doubled neodymium yttrium aluminum garnet pulse laser (12 ns full width at half-maximum). Experiments with tungsten and tantalum are presented, showing the potential of this method for imaging fast changes of local surface parameters, e.g., temperature. The emission microscope is found to be a sensitive probe for incipient laser-induced modifications of the surface, even in the conventional mode. Apart from this some technical problems as well as the physical limitations of time-resolved thermal-emission microscopy are discussed.