Characterization of Er in porous Si

The fabrication of porous Si-based Er-doped light emitting devices is a very promising developing field for all-silicon light emitters. However, while luminescence of Er-doped porous silicon devices has been demonstrated, very little attention has been devoted to the doping process itself. We have undertaken a detailed study of this process examining the porous silicon matrix from several points of view, during and after the doping. In particular, we have found that the Er doping process shows a threshold level which, as evidenced by the cross correlation of the various techniques used, does depend on the sample thickness and on the doping parameters

Implicit self-consistent electrolyte model in plane-wave density-functional theory

The ab-initio computational treatment of electrochemical systems requires an appropriate treatment of the solid/liquid interfaces. A fully quantum mechanical treatment of the interface is computationally demanding due to the large number of degrees of freedom involved. In this work, we describe a computationally efficient model where the electrode part of the interface is described at the density-functional theory (DFT) level, and the electrolyte part is represented through an implicit solvation model based on the Poisson-Boltzmann equation. We describe the implementation of the linearized Poisson-Boltzmann equation into the Vienna Ab-initio Simulation Package (VASP), a widely used DFT code, followed by validation and benchmarking of the method. To demonstrate the utility of the implicit electrolyte model, we apply it to study the surface energy of Cu crystal facets in an aqueous electrolyte as a function of applied electric potential. We show that the applied potential enables the control of the shape of nanocrystals from an octahedral to a truncated octahedral morphology with increasing potential

Seed delivery system: The key for a sustainable pulse agriculture for smallholder farmers

Seed is the life-blood of agriculture and the foundation of a successful farming for smallholder farmers. Good quality seeds, which have genetic and physical purity; health standards; high germination and moistu re percentage , can increase farmer's production by 20-30% The Green Revolution (GR) program has influenced seed supply system in the 70's in vegetables and cereals but not in pulses , which is mainly grown in the drylands. The current seed flow in pulses reveals that marketing and usage from a system of free access and/or exchange is limited to seed growers or seed producers , traders (middlemen) and agricultural government agencies...

Chickpea Production in India

Chickpea (Cicer arietinum L.), a cool season crop, is the largest produced food legume in South Asia and the third largest globally, after common bean and field pea..

Seed System Institutionalization for Pulses: A Must in the Philippines

The Green Revolution (GR) program has influenced seed system in the 70’s in vegetables and cereals but not in pulses. Seed is the fundamental life-blood of agriculture and the foundation of a successful farming for smallholder farmers in the dryland tropics. The farmer does make arrangements for many farm inputs but the seed is the primary input. Good quality seeds, which have genetic and physical purity; health standards; high germination and moisture percentage, can increase farmer’s production by about 20-30%. The procedures, through which a cultivar is bred, produced, certified, stored, marketed and used which includes all the channels through which farmers acquire genetic materials and in interaction with the commercial seed industry is known as seed system. In the Philippines, the flow of planting materials is more on the farming community as farmer seed exchanges and barter is preferred than acquiring seeds by cash. Most often the cultivars promoted are the registered seeds or good seeds, limiting the diversity in farmers’ fields. Farmers have traditionally relied on seed saving as their primary method of seed access. For pigeonpea, farmers cultivate local varieties and would trade seed amongst themselves or between villages when their seed became unviable after 2-4 years or more of successive cultivation. The trade between farmers first and then with neighboring villages helped to give new exposure to existing cultivars in the village