Additive coloring of thin, single crystalline MgO(001) films.

Electron bombardment of single-crystalline MgO(001) films has been shown to result in the formation of surface color centers. In this report we present an alternative way to produce surface color centers on single-crystalline MgO(001) films using additive Mg coloring. Electron paramagnetic resonance (EPR) spectroscopy was used to prove the formation of surface paramagnetic color centers upon deposition of small amounts of Mg on MgO(001) films at 50 K. With increasing coverage the number of Mg induced color centers rises up to a coverage of about 0.03 monolayers and thereafter decreases with increasing Mg coverage. At high coverage and low temperatures metallic Mg clusters nucleate on the surface of the MgO(001) film as shown by infrared (IR) spectroscopy using CO as a probe molecule.