Doped semiconductor nanocrystals

Doped Semiconductor Nanocrystals Synthesis, Characterization, Physical Properties, and Applications... 

Many approaches have been taken to prepare colloidal doped semiconductor nanocrystals. For example, hot-injection methods have been used to synthesize colloidal Mn2+-doped CdSe (47, 48), ZnSe (49), and PbSe (50) colloidal nanocrystals. Colloidal ZnO DMS-QDs doped with Co2+, Ni2+, and Mn2+ have been prepared by low-temperature hydrolysis and condensation (51-54). Sol-gel methods have been used to prepare colloidal doped TiC>2 (55-57) and Sn02 (58-62) nanocrystals. Inverted micelle methods have been used for preparation of a range of doped II-VI sulfide DMS-QDs at low temperatures (63-68). A high-temperature lyothermal single-source method was used to synthesize Co2+- and Eu3+-doped CdSe nanocrystals (69, 70). Autoclaving has occasionally been used to induce crystallization at lower temperatures than reached under atmospheric pressures while retaining colloidal properties, for... 

A similar result has been found using Raman spectroscopy of core-shell nanocrystals. Like XRD, Raman spectroscopy has also been widely employed to study doping of bulk semiconductors (110-112) but so far has only rarely been applied to doped semiconductor nanocrystals (70). Analogous to Vegard s law, shifts in lattice Raman vibrational energies have been found to occur with increasing dopant concentration in both the bulk and nanocrystalline materials. 

Several examples have been reported recently of solution-processed multilayer electroluminescence devices incorporating semiconductor nanocrystals as the active recombination centers (16-18, 164). Recently, attention has also turned to hybrid electroluminescent devices involving transition metal-doped nanocrystals (104, 165-167). Although many challenges remain, including more specific exploitation of the dopants in many cases, the devices demonstrated to date represent a new direction in application of doped semiconductor nanocrystals made possible by the compatibility of these luminescent nanocrystals with solution processing methodologies. 

The body of work presented in this chapter has focused largely on the synthesis of colloidal doped semiconductor nanocrystals, and on the application of a wide variety of characterization techniques to ensure dopant incorporation into the host semiconductor lattice. Although still relatively rare, the high-quality... 

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