Photoelectron diffraction studies of Ag(001), MnO(001) and epitaxial MnO films

Abstract

A joint experimental and theoretical investigation of epitaxial MnO films on Ag(001) also including the reference systems Ag(001) and MnO(001) is presented using photoelectron diffraction (XPD) supported by photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED). MnO films have been grown with thicknesses 1 to 5 nm. The conditions of film growth (temperature and time) have been chosen to obtain information on the development of film structure with thickness and to permit comparison regarding film absorption and diffraction studies. Experimental angular distribution patterns (ADP) and angular distribution curves (ADC) have been recorded and analyzed by comparing the results to multiple scattering cluster calculations. Excellent agreement was obtained for the description of the ADCs of Ag(001) and MnO(001) surfaces, and fine structures due to multiple scattering effects have been clearly identified. The multiple scattering analysis has been found to be indispensable in particular for a structural analysis of the oxide material. ADPs of MnO films grown on Ag(001) have supported the epitaxial growth of the films from the beginning. The analysis of the ADCs in dependence on growing MnO film thickness has provided clear evidence for strained, tetragonally distorted MnO films for the first few nm, while the thicker films of about 5 nm have evidently adopted bulk structure and bulk lattice constants. These results are discussed in comparison to recent structural studies of MnO on non-lattice matched metal substrates resulting in a rather similar plot for the oxide growth.