Nanocrystalline Binary, Ternary and Dilute Magnetic Semiconductors from Polychalcogenide Complexes

Abstract

The molecular polychalcogenide complexes [M(Se4)2]2−, (M=Mn, Zn, Cd, Hg), [Sn(Se4)3]2−, and [Cu4Se12]2− can be converted to the corresponding binary semiconducting solids. DMF and DMSO solutions of these complexes react with Se-abstracting reagents such as CN− and (n-Bu)3P to yield the corresponding binary solids at 155 °C or less. Appropriate stoichiometric mixtures of [Cu4Se12]2− and [In3Se15]3− react to give CulnSe2. Appropriate stoichiometric mixtures of [Cd(Se4)2]2− and [Mn(Se4)2]2− give solid solutions Cd1−xMnxSe where O<x<l. The Cd1−xMnxSe solid solutions were characterized by variable temperature magnetic measurements. Depending on the reaction conditions, metal precursor complex and Se-abstracting reagent used, the semiconductor particle size ranges from the quantum-size to the bulk regime. This method of synthesis produces the little known γ-MnSe in pure form.

Architectural Control of Magnetic Semiconductor Nanocrystals

“…Changes in the lattice constants from 4.093 to 4.083, 4.069, 4.059, and 3.873 Å for the a axis and from 6.696 to 6.675, 6.631, 6.616, and 6.376 Å for the c axis are observed with the increase in Mn composition ( x ) from 0 to 0.02, 0.08, 0.12, and 1. These trends are consistent with Vegard's law and indicate homogeneous distribution of Mn inside the CdS matrix even with 12% Mn doping. In our attempt for incorporation of much higher amounts of Mn atoms (e.g., >∼15%), however, segregation of Mn atoms out of the CdS matrix is observed.…”

Influence of Mn doping on the microstructure and optical properties of CdS

“…Changes in the lattice constants from 4.142 to 4.138 and 4.112 Å for the a-axis and from 6.724 to 6.718 and 6.693 Å for the c-axis are observed with the increase in Mn composition (x) from 0 to 0.03 and 0.05. These trends are consistent with Vegard's law and indicate homogeneous distribution of Mn inside the CdS matrix [32,33]. Fig.…”

Mn2+‐Doped CdSe Quantum Dots: New Inorganic Materials for Spin‐Electronics and Spin‐Photonics

“…this synthetic route thus appears beneficial for doping, a conclusion reminiscent of the Kanatzidis group's success in preparing Cd 1-x Mn x Se (0 x 1) nanocrystalline powders at temperatures below 155 8C. [125] The tradeoff of optimizing CdSe QD growth conditions for doping is that they are no longer necessarily optimized for producing the narrowest size distributions or for minimizing other undesired defects apart from the desired impurity ions (which are themselves defects, of course), and there is thus room for further improvement of these synthetic techniques. Although the target Mn 2þ -doped CdSe QDs can now be prepared in colloidal form, much remains to be learned about the mechanistic details of this and the other doping chemistries listed in Table 2, and this topic will undoubtedly remain a fertile subject for future research.…”

“…[126] Although the exact role of Se is not yet fully understood, it may facilitate doping through the formation of higher nuclearity inorganic clusters such as [Cd 10 Se 4 (SePh) 16 ] 4À from [Cd 4 (SePh) 10 ] 2À , [126,140] PhSe 1-oxidative elimination (e.g., forming PhSeSePh), [126,131,132] or possibly even formation of [M(Se 4 ) 2 ] 2À polychalcogenide complexes. [125] Parallel experiments involving Co 2þ dopants in place of Mn 2þ revealed the need to remove surface-bound or other adventitious Co 2þ , and showed that the commonly employed method of pyridine surface-ligand exchange is not sufficiently reliable in this task. [126] Adventitious impurity ions can be removed instead using a procedure involving TOPO as the coordinating solvent.…”