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We have investigated silicon on iron (Si-on-Fe) and iron on silicon (Fe-on-Si) interfaces in Fe/Si multilayer(ML) structures. Fe/Si MLs of various Fe and Si layer thicknesses are deposited by the ion beam deposition technique. Structural information on the interfaces is obtained using grazing incidence x-ray reflectivity, x-ray standing wave and cross-sectional transmission electron microscopy measurements. Interdiffusion is greater at the Si-on-Fe interface compared with the Fe-on-Si interface. Silicide interlayer formation is observed at both interfaces. FeSi is the main component of interfacial silicide. The presence of crystalline FeSi and Fe2Si is observed.

We have investigated the nature of silicon on iron interface in electron beam deposited Fe∕Si bilayers, with various iron and silicon thicknesses. The Fe and Si layer thicknesses are varied from 30to330Å and 20to86Å, respectively. Grazing incidence x-ray reflectivity and photoelectron spectroscopy measurements were carried out on these samples to determine interface characteristics. Si on Fe (Si̱Fe) interlayer thickness, roughness, and composition do not depend on the thickness of Fe and Si. The thickness of the interlayer is around 13Å. A systematic variation in silicide concentration across this interface is observed by x-ray photoelectron spectroscopy measurement. Change in the density of states in valence band across this interface is also observed by ultraviolet photoelectron measurement.

Bacillus thuringiensis var. kenyae (B.t.k.) is a microbial insecticide effective against lepidopteran pest species. Acute oral toxicity in rats and acute dermal toxicity, ocular irritation, skin irritation in rabbits were studied for the wettable powder formulation of B.t.k. In addition, toxicity of the wettable powder formulation was also studied in fresh water fish (Gambussia affinis). The results of these studies indicate that this wettable powder formulation of B.t.k. is nontoxic and nonirritant to rats, rabbits, and fish.