Improved depth resolution by sample rotation during Auger electron spectroscopy depth profiling

Abstract

The surface topography of an analysed sample has a very strong influence on the depth resolution, because of the angular distribution of the microplanes and the amplitude of the roughness. To diminish the topographical effect, commercial Auger electron spectroscopy (AES) apparatuses are nowadays equipped with two ion guns, each symmetrically inclined to the surface normal. The theoretical and fundamental work carried out in the field of AES depth profile analysis in recent years shows that a further improvement in depth resolution could be obtained by sample rotation during ion sputtering. Because of technical difficulties AES depth profiling with simultaneous sample rotation has not been attempted earlier. We equipped a sample holder with a special mechanism which enables sample rotation during depth analysis. Samples of multilayer Cr/Ni thin film structures deposited onto rough and smooth silicon substrate were rotated at a speed of 1 rev min -1 during depth profile analysis by AES and argon ion sputtering. We encountered some experimental difficulties due to changes in the peak-to-peak heights during sample rotation. However, the results of these first investigations clearly show that sample rotation during ion sputtering considerably improves the depth resolution of AES composition-depth profiles. We consider that sample rotation should be introduced into everyday analytical practice to approach real depth profiles.