We report the realization of free standing 3D structures as tall as ∼ 7μm with nano-scale thickness in Si using the technique of Ga focused ion beam implantation and sputtering followed by wet chemical etching. Some of the previously investigated subjects such as anisotropie etching behavior of crystalline Si and etch stop effect of Ga+implanted Si etched in certain anisotropie chemical etchants have been further explored with the emphasis on exploiting them in realizing free standing structures. The design and fabrication considerations in achieving such free standing structures are discussed and some typical structures fabricated by this technique are shown.
We have studied how a surfactant (Aerosol OT or AOT) self-assembles in different polar (Water, Ethylene glycol, Formamide, N, N-Dimethylformamide) and non-polar (Isooctane) solvents. AOT is a widely used surfactant in biological and industrial applications. The lamellar phase of the AOT/water system is often used as a model of lipidic membrane. We investigated two surfactant volume fractions (0.2 and 0.6) with visual inspection, SAXS, rheology and electrical conductivity experiments. The results indicate that AOT selfassembles differently depending on solvent type and concentration. SAXS experiments show that the AOT/water systems display lamellar phases. In the other cases, only formamide displays a lamellar phase for 4 = 0.6. The other solvents (and formamide at 4= 0.2) promote the self-assembly of AOT in other microstructures. In these cases, the SAXS spectra display correlation peaks consistent with a disordered array of cylindrical aggregates. The visual inspection, rheology and electrical conductivity results are consistent with the deduced self-assembled structures. We explain most of our results in terms of surfactant packing models and solvent properties.
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