Soft x-ray appearance potential spectroscopy study of NiO and CoO single crystal surfaces

Abstract

Soft x-ray appearance potential spectroscopy (SXAPS) spectra of Ni 2p, Co 2p, and O 1s for NiO and CoO single crystal surfaces have been measured. Two peaks and a shoulder along with two core lines due to 2p3/2 and 2p1/2 are found for a Ni 2p raw spectrum. A Ni 2p metallic edge was observed for the NiO surface sputtered by Ar ions. An O 1s spectrum of NiO exhibits a broad peak between about 522 and 550 eV and the self-deconvoluted spectrum shows five peaks. For the Co 2p spectrum, two core lines due to 2p3/2 and 2p1/2 along with a shoulder are found and the self-deconvoluted spectrum exhibits four peaks. The broad peak is also seen between about 525 and 555 eV for the O 1s spectrum of CoO and the self-deconvoluted spectrum shows four peaks. The features of the self-deconvoluted SXAPS spectra of Ni 2p, Co 2p, and O 1s for NiO and CoO are found to resemble those of the corresponding near edge x-ray absorption fine structure (NEXAFS). The origin of the peaks is discussed to compare the present work with the previous theoretical calculations for the NEXAFS spectra.