Aspects of lateral resolution in energy-filtered core level photoelectron emission microscopy

Lateral resolution is a major issue in photoelectron emission microscopy (PEEM) and received much attention in the past; however a reliable practical methodology allowing for inter-laboratory comparisons is still lacking. In modern, energy-filtered instruments, core level or valence electrons give much lower signal levels than secondary electrons used in still most of the present experiments. A quantitative measurement of the practical resolution obtained with core level electrons is needed. Here, we report on critical measurements of the practical lateral resolution measured for certified semiconducting test patterns using core level photoelectrons imaged with synchrotron radiation and an x-ray PEEM instrument with an aberration-corrected energy filter. The resolution is 250 ± 20 nm and the sensitivity, 38 nm. The different contributions to the effective lateral resolution (electron optics, sample surface imperfections, counting statistics) are presented and quantitatively discussed.