Location of Trapped Electron Centers in the Bulk of Epitaxial MgO(001) Films Grown on Mo(001) Usingin situW-band Electron Paramagnetic Resonance Spectroscopy

Abstract

We present the first in situ W-band (94-GHz) electron paramagnetic resonance (EPR) study of a trapped electron center in thin MgO(001) films. The improved resolution of the high-field EPR experiments proves that the signal originate from a well-defined species present in the bulk of the films, whose projection of the principal g-tensor components onto the (001) plane are oriented along the [110] direction of the MgO lattice. Based on a comparison between the structural properties of the films, knowledge of the ability of bulk defects to trap electrons, and the properties of the EPR signal, it is possible to propose that the paramagnetic species are located at the origin of a screw dislocation in the bulk of the film.

Chapter model systems in heterogeneous catalysis at the atomic level: a personal view

“…Figure 8(b) shows a comparison between X-band (top) and W-band spectra (below) of MgO color centers located in the bulk of the MgO film. From a detailed g-tensor analysis as well as angle dependent measurements (see Figure 8(c)), we concluded that those species are located at screw dislocations inside the MgO film [26].…”

“…In order to improve on resolution, it was necessary to move to higher magnetic fields (W-band, 94 GHz). The reduced wavelength of the radiation introduces additional constraints which required to develop an appropriate re-sonator structure [25,26]. However, it has been possible to set up a working spectrometer (Figure 3(b)) and proving its ability to improve spectral resolution using color centers in oxides as a model system.…”

“…[25], copyright by AIP Publishing (2014), adapted with permission from Ref. [26], copyright by American Physical Society (2016) (color online).…”

“…Curve (a) displays the IRAS spectrum which was obtained via dividing the spectrum of the pristine V 2 O 3 (0001) film, the sample spectrum, by a reference spectrum, which was a spectrum of the V 2 O 3 (0001) film with the vanadyl oxygen atoms removed by electron bombardment [65]. The reduced film still contains some isolated V=O groups on the [26,42], adapted with permission from Ref. [26], copyright by American Physical Society (2016), adapted with permission from Ref.…”

“…The reduced film still contains some isolated V=O groups on the [26,42], adapted with permission from Ref. [26], copyright by American Physical Society (2016), adapted with permission from Ref. [42], copyright by John Wiley and Sons (2011) (color online).…”