The influence of boron-induced dislocation loops on the luminescence efficiency of silicon-based light-emitting diodes is investigated. Luminescence measurements and transmission-electron-microscopy ...images from devices fabricated by boron implantation into crystalline silicon, and subsequently processed under different conditions to form dislocation loops of different size and densities, were compared. Light emitting devices were also fabricated in an otherwise identical but a pre-amorphized substrate, to prevent boron-induced loop formation. The results demonstrate a strong correlation between the dislocation loop density and areal coverage, and the light emission efficiency. The devices produced in the pre-amorphized substrate, without dislocation loops, show strongly quenched light emission.
In this paper, a general overview of the technologies surrounding light emission in silicon-based systems is presented with an indication as to the applications for which they may be used. Special ...attention is given to the use of dislocation engineering, where, through the use of additional dopants, not only can 1150-nm band edge emission be achieved but tuning of the wavelength to accommodate telecommunications applications is also possible. Details of the impact of implantation energy and dose are demonstrated together with post implant anneal studies to optimise the process for light generation. Finally, dislocation engineering is applied to silicon on insulator (SOI), the most common optical platform.
We examine the relationship between poverty and the use of wild foods, namely bushmeat, fish and wild plants, within a Congolese agricultural community. A sample of 121 households were monitored over ...a 16-month period, using a combination of participatory and quantitative survey techniques, to assess their wealth and their production, consumption and market sales of wild foods. Households varied in wealth but all could be considered subject to extreme poverty (income below US$1 per capita per day). Our analyses indicate that wild foods play a small role in household consumption but a major role in household income. Hence, over 90% of both bushmeat and fish production is sold at market. In addition, the value of wild foods increases in the “lean season” when agricultural production is low. We also find that the poorest households in this community are unable to capitalise on the most valuable wild foods, bushmeat and fish, as a source of food or cash income. We use an entitlements framework to explain the factors that determine such wealth-related variation between households, indicating that household use of wild foods is determined more by social and economic constraints than by resource abundance in this community. Nevertheless, our findings show that overall the small-scale commercialisation of wild foods provides a vital source of income for rural households living in extreme poverty.
Ion beam fabricated silicon light emitting diodes Lourenço, M. A.; Siddiqui, M. S. A.; Shao, G. ...
Physica status solidi. A, Applied research,
01/2004, Letnik:
201, Številka:
2
Journal Article, Conference Proceeding
Nanometer-sized beta-FeSi2 precipitates are formed in Si by ion beam synthesis (IBS). A systematic study is carried out to investigate the correlation among the implantation parameters, the ...microstructure, and the luminescence properties. On the one hand, we found additional orientation relationships (ORs) appear between the beta-FeSi2 and the Si with improved lattice coherence between the two, when the ion implantation energy is increased. On the other hand, the degree of preferential orientation deteriorates and leads to poor lattice coherence between the particles and Si matrix when the iron ion is overdosed. These microstructure changes lead to different luminescence properties (intensity, peak position and shape) of the beta-FeSi2 particles accordingly.
PDF