Comparison of rotational depth profiling with AES and XPS

After successful applications of depth profiling with sample rotation in AES and SIMS we used this technique in XPS, too. Until now, most of the experimental work with rotational depth profiling has been done by AES. It was conclusively shown that the technique enables high depth resolution which is independent of sputtered depth due to reduced ion-beam-induced topography effects. AES and XPS differ in some instrumental details and experimental conditions, however, the most important difference with respect to profiling is that of the analysed area, which is, even in the case of small-spot XPS instruments, much larger than in AES. This results in a decisive distortional influence of crater-edge effects on XPS depth profiles obtained on stationary and/or rotated samples, and is recognized in an increasing degradation of depth resolution with sputtered depth. The importance of alignment of the probe beam, analysed spot, ion beam and rotation axis is discussed and is demonstrated by comparison of the results of rotational depth profiling of a Ni/Cr multilayer structure with AES and XPS.