Preparation and characterization of stable aqueous suspensions of up-converting Er3+/Yb3+-doped LiNbO3 nanocrystals

The preparation of LiNbO3:Er3+/Yb3+ nanocrystals and their up-conversion properties have been studied. It is demonstrated that polyethyleneimine- (PEI) assisted dispersion procedures allow obtaining stable aqueous LiNbO3:Er3+/Yb3+ powder suspensions, with average size particles well below the micron range (100���200 nm) and the isoelectric point of the suspension reaching values well above pH 7. After excitation of Yb3+ ions at a wavelength of 980 nm, the suspensions exhibit efficient, and stable, IR-to-visible (green and red) up-conversion properties, easily observed by the naked eye, very similar to those of the starting crystalline bulk material.

Doping in MARCA (1975-1990)

En el estudio hist��rico del dopaje en Espa��a, conocer el papel de los medios de comunicaci��n escritos, como el diario deportivo Marca, resulta ser de gran relevancia. La funci��n que el peri��dico m��s vendido en Espa��a ha desempe��ado a lo largo de los a��os con relaci��n al deportista sospechoso, permite conocer de qu�� manera el discurso social se ha estructurado bas��ndose precisamente en c��mo sus cronistas han narrado el caso de dopaje.

Optimizing phosphorus diffusion for photovoltaic applications: peak doping, inactive phosphorus,gettering, and contact formation

The phosphosilicate glass (PSG), fabricated by tube furnace diffusion using a POCl3 source, is widely used as a dopant source in the manufacturing of crystalline silicon solar cells. Although it has been a widely addressed research topic for a long time, there is still lack of a comprehensive understanding of aspects such as the growth, the chemical composition, possible phosphorus depletion, the resulting in-diffused phosphorus profiles, the gettering behavior in silicon, and finally the metal-contact formation. This paper addresses these different aspects simultaneously to further optimize process conditions for photovoltaic applications. To do so, a wide range of experimental data is used and combined with device and process simulations, leading to a more comprehensive interpretation. The results show that slight changes in the PSG process conditions can produce high-quality emitters. It is predicted that PSG processes at 860�����C for 60���min in combination with an etch-back and laser doping from PSG layer results in high-quality emitters with a peak dopant density Npeak���=���8.0��������1018���cm���3 and a junction depth dj���=���0.4�����m, resulting in a sheet resistivity��sh���=���380 ��/sq and a saturation current-density J0 below 10 fA/cm2. With these properties, the POCl3 process can compete with ion implantation or doped oxide approaches.