Experimental setups for XPS measurements beyond the instrumental lateral resolution limit

Abstract

The lateral resolution of an X‐ray photoelectron spectroscopy instrument, which is equipped with a focused X‐ray beam, is limited by the nominal X‐ray beam diameter and the long tail intensity distribution of the X‐ray beam. The long tail intensity distribution of the X‐ray beam impedes to perform a measurement with good lateral resolution and low detection limits at the same time. Two experimental setups are described which allow examining sample structures that are smaller than the X‐ray beam dimensions. The first method uses differential sample charging on partly nonconductive samples by low‐energy electron flooding. The spectra of the nonconductive sample areas are shifted towards lower binding energy. That way, the surface composition of conductive and nonconductive sample areas are estimated independently. The second method utilizes the rather limited dimensions of the energy analyser acceptance volume. Here, only the sample is placed inside the energy analyser acceptance volume. That way, signals from the illuminated sample contribute exclusively to the measured photoelectrons intensity, independent from the sample size.