High-frequency EPR, ESE, and ENDOR spectroscopy of Co- and Mn-doped ZnO quantum dots

Co- and Mn-doped ZnO quantum dots (QDs) with ZnO/Zn(OH)(2) core-shell structure were studied using high-frequency electron paramagnetic resonance (EPR), electron spin echo, and electron-nuclear double resonance (ENDOR) at low temperature. The shape of the EPR spectrum of cobalt ions was observed to change as a result of Co2+ coupling with optically created shallow donors (SDs). This, along with a shift of SDs line, is a direct demonstration of interaction between the magnetic ion and donor electron in confined system of ZnO QD. ENDOR resonance of the H-1 hydrogen nuclei detected by the EPR signal of Co2+ and Mn2+ evidence the hyperfine coupling between these ions, located in the ZnO core, and the protons outside the quantum dot core in the shell. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim