QUANTITATIVE NEAR-SURFACE MICROANALYSIS AND DEPTH PROFILING BY EPMA

This paper presents a review of developments in thin film analysis by EPMA during the last 15 years and reports on the capabilities and limi tations of the technique when applied to the quantitative analysis of thin coatings, multilayers and oxide layers. During the development of thin film EPMA it was always intended to apply EPMA to the analysis o f elemental depth distributions in the submicron range. It is pointed out that the technique of electron beam energy variation is clearly li mited to cases where some pre-information on the structure of the mate rial or the shape of the depth profiles is available. For real EPMA-de pth profiling in the depth range of 1 mu m to a few mu m, mechanical b evelling of the sample and analysis with low, carefully chosen beam en ergies is recommended as a useful technique, which is demonstrated her e by application to a multilayered hard coating. For a more general ap plication of EPMA depth profiling to the submicron range, a combinatio n of X-ray microanalysis with ion beam sputtering has been introduced recently. This technique increases the sensitivity of EPMA to detect v ariations in element distributions with depth and combines its capabil ity of accurately quantifying element coverage with a better depth res olution. It is shown that with EPMA sputter depth profiling quantitati ve depth profiles can be deduced from calibrated X-ray intensity measu rements without needing a priori information on sputter rates. This de velopment, with its ability to quantify both composition and depth sca le, complements the well established methods of surface analysis. The paper reveiws first attempts in combining X-ray analysis with Auger de pth profiling, introduces the basic principles and presents results fr om a quantitative depth profile analysis of an oxide layer on a techni cal Ti-Al-N hard coating; these results are compared with an SNMS anal ysis.