Structural properties of Bi2-xMnxSe3 thin films grown via molecular beam epitaxy

The effects of Mn doping on the structural properties of the topological insulator Bi2Se3 in thin film form were studied in samples grown via molecular beam epitaxy. Extended x-ray absorption fine structure measurements, supported by density functional theory calculations, indicate that preferential incorporation occurs substitutionally in Bi sites across the entire film volume. This finding is consistent with x-ray diffraction measurements which show that the out of plane lattice constant expands while the in plane lattice constant contracts as the Mn concentration is increased. X-ray photoelectron spectroscopy indicates that the Mn valency is 2+ and that the Mn bonding is similar to that in MnSe. The expansion along the out of plane direction is most likely due to weakening of the Van der Waals interactions between adjacent Se planes. Transport measurements are consistent with this Mn 2+ substitution of Bi sites if additional structural defects induced by this substitution are taken into account. (C) 2015 AIP Publishing LLC.