The state of the art in the synthesis of colloidal semiconductor nanocrystals. Colloidal semiconductor nanocrystals, also known as quantum dots, have attracted great attention since they have interesting size-dependent properties due to the quantum confinement effect. These nanoparticles are highly luminescent and have potential applications in different technological areas, including biological labeling, light-emitting diodes and photovoltaic devices. The synthetic methods of semiconductor nanocrystals have progressed in the last 30 years, and several protocols were developed to synthesize monodisperse nanocrystals with good optical properties, different compositions and morphologies. This review describes the main methods used to synthesize nanocrystals in the II-VI and III-V systems, and the recent approaches in this field of research. Keywords: semiconductor nanocrystals; quantum dots; colloidal synthesis.
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Magnetic semiconductors have attracted the attention of scientists in recent years due, mainly, to technological applications in the field of spintronics. These semiconductors can be developed by a process called doping, where some atoms of the semiconductor matrix are randomly replaced by magnetic Semicondutores - Dopagem. These semiconductors can be developed by a process called doping, where some atoms of the semiconductor matrix are randomly replaced by magnetic atoms.
This property enables the fabrication of a manifold of electronic devices from the same semiconductor material. The synthesis was performed using three types of milling tools which influenced the outcome of the reactions.
Samples of Fe2O3-doped TiO2 were processed using a jar of polyacetal and zirconia spheres. However, the energy produced by these tools was not sufficient to complete the formation of the compound.
Samples of TiO2 doped with Fe2O3 were successfully produced using stainless steel jar and spheres. The final compound was find to be contaminated with metallic iron impurities from the tools used. Furthermore, these impurities contributed to the formation of another phase, ilmenite FeTiO3.
To achieve purity, the samples were HCl washed for removal of metallic iron, but the phase related to ilmenite was not eliminated. These simples showed no undesirable impurities and no formation of other phases. It was also observed the formation of oxygen deficient sites in the final compounds that may be attributed to long milling times or to stoichiometric imbalance between the precursor compounds used in the milling processes. Vasconcelos, Igor Frota de.
Semicondutores / Eletrônicos