Specific effects of Cr3+ dopant ions on diluted magnetic semiconductor Sb2-xCrxTe3 quantum dots in a glass matrix

Abstract

Sb2-xCrxTe3 quantum dots (QDs) were synthesized in a host glass matrix through fusion and heat treatment methods. The results revealed the specific effects inherent to the doping of Cr3+ ions in diluted magnetic semiconductors (DMS) (Sb2-xCrxTe3 QDs embedded in glass matrix). Differential Thermal Analysis shows evidence of changes in glass transition and the host glass's crystallization temperatures with the presence of Sb2-xCrxTe3 QDs. Transmission electron microscopy (TEM) images and energy dispersive X-ray analysis evidenced the formation, size, and composition of these DMS QDs. The interplanar distances dhkl measured in TEM and the pattern observed in electron diffraction from the selected area reinforces the Sb2Te3 crystalline nature. Structural analyses of x-ray diffraction patterns confirm that all Sb2-xCrxTe3 QDs crystallize in the rhombohedral R3_m−D3d5 structure and that Cr3+-ions had replaced Sb3+-ions. Electronic paramagnetic resonance (EPR) spectra exhibit resonance signals confirming Cr3+ ion incorporation into the Sb2Te3 crystal lattice. Moreover, EPR shows that the sp-d exchange interactions become less pronounced with the formation of Cr3+ ─ Cr3+ pairs. Raman scattering spectroscopy confirmed the formation of Sb2-xCrxTe3 QDs. The red and blue shifts of the normal Raman- and IR-active vibrational modes characteristic of Sb2Te3 give strong evidence of the Cr3+ ion incorporation in QDs. Interestingly, the study results revealed better structural and magnetic properties. We believe that these Sb2-xCrxTe3 QDs in SNAB glass, with appropriate dopant concentration and chemical composition, are potentially efficient for thermoelectric, topological insulators, photovoltaic devices, solar cells, magnetic devices and spintronic applications.