UHV-Cleaved Single Crystal MgO(100) by Electron Energy Loss Spectroscopy

Abstract

Interband electron energy loss (EELS) spectra probe the joint density-of-states between the initial and final electron states. In the wide scan spectrum, the structure between 0 and about 50 eV loss energy corresponds to transitions originating in the O 2p valence band. Between 50 and 80 eV, the initial state is the Mg 2p core level, and above about 90 eV the initial state is the Mg 2s. EELS is also very sensitive to small concentrations of defects on the MgO surface. The narrow scan spectrum of the clean, cleaved surface exhibits a surface-defect loss feature in the 1–2 eV region which is sometimes present on UHV-cleaved (or ion-bombarded) surfaces; that feature is not present on the cleaved surface used for the wide scan. After exposure to O2, the defect loss feature has essentially disappeared, with only minor changes in the rest of the spectrum. [See V. E. Henrich and R. L. Kurtz, J. Vac. Sci. Technol. 18, 416 (1981), for a discussion of the nature of the surface defects.]