Articles you may be interested inThe effects of high temperature processing on the structural and optical properties of oxygenated CdS window layers in CdTe solar cells

Doping is a technique that makes it possible to incorporate substitutional ions into the crystalline structure of materials, generating exciting properties. This book chapter will comment on the transition metals (TM) doped nanocrystals (NCs) and how doping and concentration influence applications and biocompatibility. In the NCs doped with TM, there is a strong interaction of sp-d exchange between the NCs’ charge carriers and the unpaired electrons of the MT, generating new and exciting properties. These doped NCs can be nanopowders or be embedded in glass matrices, depending on the application of interest. Therefore, we show the group results of synthesis, characterization, and applications of iron or copper-doped ZnO nanopowders and chromium-doped Bi2S3, nickel-doped ZnTe, and manganese-doped CdTe quantum dots in the glass matrices.

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In this work, we used nominal concentration (x) and thermal annealing to control the density of manganese (Mn 2+ ) ions and cadmium vacancies (V Cds ) in Cd 1−x Mn x Te ultrasmall quantum dots (USQDs) embedded in a glass matrix. The physical properties were investigated by photoluminescence (PL) and electron paramagnetic resonance (EPR). PL bands related to surface defects and Mn 2+ ions intensified, whereas bands related to V Cds decreased with increasing manganese concentration. Longer thermal annealing times caused decreases in the intensity of PL bands characteristic of Mn 2+ ions and V Cds . The EPR spectra confirmed that manganese exhibited +2 oxidation states and was incorporated at the core and surface of the Cd 1−x Mn x Te USQDs. Furthermore, the quantities of Mn 2+ ions within the Cd 1−x Mn x Te USQDs confirmed that longer thermal annealing times were associated with constant diffusion of these ions from the core to the surface and then the glass. Therefore, we demonstrated that longer thermal annealing times and higher manganese concentrations make it possible to control both the emissions intensities related to V Cds and Mn 2+ ions and the diffusion of these ions to the surface and then the glass. ■ INTRODUCTIONDiluted magnetic semiconductor (DMS) nanocrystals (NCs) are materials in which some sites are substituted by impurities, typically manganese. DMSs are represented by A 1−x Mn x B, where x denotes the fraction of impurities. Manganese with +2 oxidation states (Mn 2+ ions) is easily incorporated into the II− VI NCs by replacing group II cations. When Mn 2+ ions occupy Cd sites in a cubic CdTe crystal, their free-ion terms split due to the cubic crystal field. 1 Manganese-doped II−VI and III−V semiconductor NCs have been studied extensively because of their interesting properties and numerous applications. 2−5 For example, group II cations (Zn, Cd, and Hg) and group VI anions (S, Se, and Te) doped with Mn 2+ ions have been used in magneto-optical devices. 6 Diverse applications are possible because of the exchange interaction between the electronic subsystem (sp-band electrons of the host semiconductor) and the electrons originating in the partially filled d or f levels of the magnetic ions constituting the DMS. This exchange interaction enables control over the electronic and optical properties of the material using external magnetic fields.The optical properties of semiconductor NCs can be altered by quantum confinement effects, which are tuned to the size and shape of nanocrystals called quantum dots (QDs). Regarding DMS, exchange interactions between magnetic ions and host nonmagnetic semiconductors strengthen as NC sizes diminish. Furthermore, the electronic paramagnetic resonance (EPR) technique showed these ions may be incorporated at different crystallographic sites within the crystal, (e.g., in the nucleus or at the surface). Thus, identifying these magnetic ions makes it possible to trace their migration from the core to the surface regions of the NCs and to quantify their local densitie...

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