Comparative studies of optical absorption, photoluminescence and EPR spectra of PbMnI₂ bulk layers and nanocrystals

Abstract

We report a study of the layered diluted magnetic semiconductor (DMS) Pb₁₋xMnxI₂ in 3D bulk layers and nanocrystal form by using optical absorption, photoluminescence and electron paramagnetic resonance (EPR). The samples of the bulk Pb₁₋xMnxI₂ crystals with x lying within the range 0 to 0.15 were grown using the Bridgman-Stockbarger technique. The composite nanostructures containing DMS nanocrystals of Pb₁₋xMnxI₂ were prepared by cooling the boiling saturated aqueous solution to room temperature. The exciton structure of the absorption spectra of nanoparticles exhibits blue shift due to the quantum confinement effect. In photoluminescence spectra of nanocrystals, two main peaks were revealed, which are attributed to the band-edge transitions and defect states. The EPR spectra for bulk layers and nanocrystals consist of an intense broad line and several weak narrow lines that correspond to hyperfine spectra of Mn²⁺ ions.