Characterization of surface chemical states of a thick insulator: Chemical state imaging on MgO surface

We report a surface characterization tool that can be effectively used to investigate the chemical state and subtle radiation damage on a thick insulator surface. It has been used to examine the MgO surface of a plasma display panel (PDF) consisting of a stack of insulator layers of approximately 51 μm thickness on a 2-mm-thick glass plate. The scanning photoelectron microscopy (SPEM) image of the insulating MgO surface was obtained by using the difference in Au 4f peak shift due to the surface charging at each pixel, where a Au adlayer of approximately 15 Å thickness was formed on the surface to overcome the serious charging shift of the peak position and the spectral deterioration in the photoelectron spectra. The observed contrast in the SPEM image reveals the chemical modification of the underlying MgO surface induced by the plasma discharge damage. The chemical state analysis of the MgO surface was carried out by comparing the Mg 2p, C 1s and O 1s photoemission spectra collected at each pixel of the SPEM image. We assigned four suboxide phases, MgO, MgCO₃, Mg(OH)₂ and Mg¹⁺, on the initial MgO surface, where the Mg(OH)₂ and Mg¹⁺ phases vanished rapidly as the dischargeinduced surface damage began.