Strong Laser Fields
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Demonstration of 3-D Resolved Element Analysis of Material Surfaces by Laser-Postionization of Sputtered Neutrals
U. Müller, M. Schittenhelm, R. Schmittgens and H. Helm
Department of Molecular and Optical Physics, Albert-Ludwigs-Universität, Hermann-Herder-Strasse 3, D-79104  Freiburg, Germany

Abstract:


We have developed a surface analysis system that allows us to analyse the elemental composition of a sample with three-dimensional spatial resolution. The neutral material sputtered from a sample surface by Ga+ ion impact is post-ionized by non-resonant multiphoton ionization with an ArF excimer laser at 193 nm. The photoions are selected by time-of-flight mass spectrometry. Lateral resolution is achieved by scanning the surface with the tightly focused primary ion beam. The depth analysis is achieved by sequentially removing layers of material and sweeping the unfocused ion beam over the sample surface, interleaved with raster scanning the ion beam.
We tested the performance of the apparatus by analysing the surface of a pixel detector for x-ray imaging. The sample consists of an array of Ti/Al Schottky contacts grown on a GaAs substrate. We measured the distributions of elements Al, Ti, Ga and As in three dimensions over a lateral area of 150 x 150 μm2. The depth resolution was 20 nm and the lateral resolution was 3 μ, which does not yet approach the limitations of the apparatus. This demonstrates for the first time that three-dimensional imaging of the element distribution of a large area sample is feasible with high spatial and depth resolution by laser post-ionization of sputtered neutrals. © 1999 John Wiley & Sons, Ltd.


©1999Surface and Interface Analysis 27, 904 (1999)

Published Online: 24 Sep 1999
DOI: 10.1002/(SICI)1096-9918(199910)27:10<904::AID-SIA647>3.0.CO;2-U
PACS; 81.70 Jb; 79.20 Rf; 82.80 Ms; 82.50 Fv; 85.40 Ls;


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