Local zincblende coordination in heteroepitaxial wurtzite Zn 1−x Mg x O:Mn thin films with 0.01 ≤ x ≤ 0.04 identified by electron paramagnetic resonance

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 3; no. 45; pp. 11918 - 11929
• Main Authors: Böttcher, Rolf, Lorenz, Michael, Pöppl, Andreas, Spemann, Daniel, Grundmann, Marius
• Format: Journal Article
• Language: English
• Published: 2015
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/C5TC02720A

Zn 1−x Mg x O:Mn thin films with atomic Mg content x below about 0.3 are well known to crystallize in the hexagonal wurtzite structure. Here we demonstrate that beginning with a chemical Mg content of already x = 0.01 in heteroepitaxial Zn 1−x Mg x O:Mn thin films, a local cubic zincblende coordination of the Mn ion can be identified using electron paramagnetic resonance of Mn 2+ ions. The appearance of a cubic Mn 2+ spectrum in the wurtzite (Zn,Mg)O films is attributed to an enhanced formation of stacking faults providing zincblende structure locally. The Mn 2+ ions are incorporated at zinc lattice sites into the Zn 1−x Mg x O films and their zero field spitting allows to monitor even small structural changes in the MnO 4 tetrahedrons. Alloying with the smaller Mg 2+ ions leads to a shrinking of the Mn–O bond length in dependence on the axial distortion of the parent ZnO 4 . Our findings generally show that Mn 2+ ions in low concentration represent a highly sensitive paramagnetic probe in group II–VI thin films.