Das Kurzzeit-Spiegelelektronenmikroskop [article]

Harry Kleinschmidt, Oleg Bostanjoglo, Technische Universität Berlin, Technische Universität Berlin
A pulsed mirror electron microscope was developed for imaging pulse laser-induced transient processes in the nanosecond time scale. The required short illuminating electron pulses (10 ns, 10^-3 rad, 1 mA max.) are produced by treating a photocathode with ultraviolet laser pulses (lambda = 266 nm, 10 ns FWHM). The specimen is the negative electrode of a 2-electrode mirror. The processes to be studied are launched by laser pulses (532 nm, 25 ns FWHM) focussed at the surface of the specimen. The
more » ... the specimen. The illuminating and imaging electron paths are separated by an 90° magnetic prism. The Schlieren image of the specimen is projected to a phosphor screen, which is coupled to an intensified CCD via fiber optics. The space/time resolution limited by electron shot noise and illumination aperture is 1µm/10 ns. Bulk materials (stainless steel, Si) and vapour-deposited films (Al, Bi, Cr, Ni) were investigated by this mirror electron microscope. The transient surface processes observed there, like evaporation and expansion of gas clouds, removal and growth of thin adsorbate and oxide layers (even from one monolayer on), and ripping of films, show its potential as both fast and sensitive surface probe.
doi:10.14279/depositonce-686 fatcat:n6xaxtjezrfr3n7w73wf4udnje