Spectroscopic and structural implications of hosting Zn2+, Cd2+ and Hg2+ ions in the AgInS2 quantum dots

Abstract

This work address the issue of spectral implications provided by doping AgInS 2 QDs with Zn 2+ and its higher homologues including Cd 2+ and Hg 2+ . The impact of alloying AgInS 2 QD with IIB group atoms is here discussed in terms of comprehensive spectroscopic measurements as well as theoretical predictions performed within the Density Functional Theory. It is shown that each of the admixtures used induces a completely different spectral response including complete reversal character for Cd 2+ and Hg 2+ ions. Observed differences were here associated with changes in the native defects structure and possible relaxation pathways due to doping. It is shown that Zn 2+ ions results in quite weak impact on the emission properties of the AgInS 2 QDs. Highest impact was found for Cd 2+ and Hg 2+ ions. Doping AgInS 2 QDs with Cd 2+ results in successive deactivation of the relaxation pathways which were typical for pristine AgInS 2 QDs leading to significant shortening of the photoluminescence lifetime and partial band symmetrisation. Doping with Hg 2+ ions was found to be of completely opposite character. It was found that mercury adatom has the lowest affinity to the AgInS 2 surface giving rise to formation of metallic Hg-Ag complexes on a surface which may be responsible for anomalous behaviour of Hg-doped AgInS 2 QDs. • Alloying AgInS 2 QDs with Cd and Hg is of different nature to that observed for Zn. • Spectral changes induced by Zn, Cd and Hg alloying are caused by native defects. • Doping with Zn, Cd and Hg ions may either partially passivate or induce defects formation. • Both Cd and Hg ions have much stronger impact on the defects structure than Zn ions. • Mercury dopants form metallic Hg-Ag complexes in AgInS 2 resulting in spectral redshift.