Abstract
A quarter century has passed since the principle of EUPS (extreme UV excited photoelectron spectroscopy) was invented as the most promising application of a laser-produced plasma source. EUPS enables analysis of electronic states of the topmost atomic layer, band bending of semiconductors, estimation of carrier density, and evaluation of electrical conductivity from secondary electron signals. These newly emerged analyses provide useful information for developing catalysts, protective insulators and other materials. These new analyses were born when problems needed to be solved were brought in by users. We can say that EUPS was sophisticated by the needs of users. In this paper, we describe the historical background leading to the invention of the principle of EUPS, the selection and development of the component technologies that constitute the EUPS system, and the birth processes of novel analyses that emerged.
