Depending on the dopant concentration, two distinct types of porous silicon can be formed during the anodization of silicon in hydrofluoric acid. A range of samples of both types of porous silicon has been investigated using x-ray double crystal diffraction techniques. The crystal lattice of porous silicon is found to be tetragonally distorted. In the plane of the substrate, the interplanar spacing of the porous film is identical to that of the substrate but is increased in the direction normal to it. The increase is typically 700 ppm in the type of film formed on heavily doped silicon and 6000 ppm in that on lightly doped silicon. We propose that stresses, generated by the growth of a native oxide on the surface of the pores, are responsible for the observed increase in lattice parameter. The different interplanar spacings of the two types of film are related to the observed differences in their oxygen contents which are a consequence of their different surface area to volume ratios.
A transmission electron microscopy study of porous silicon reveals that pores selectively propagate in the 〈100〉 crystallographic directions on both n- and p-type silicon, indep...
Ordered microfibrils are formed on the membrane of the cytoplasmic tail of the alga Poteriochromonas after attachment to a substrate. The ultrastructure of native and extracted ...
The solid-state behaviour of 2-chloro-4-nitrobenzoic (2c4n) acid has been reinvestigated. Infrared spectra, differential scanning calorimetry (DSC), and thermomicroscopy investi...
Double-walled carbon nanotubes (DWNTs) doped with nitrogen and boron have been prepared by the decomposition of a CH(4) + Ar mixture along with pyridine (or NH(3)) and diborane,...
Covalent organic frameworks (COFs) have been designed and successfully synthesized by condensation reactions of phenyl diboronic acid {C 6 H 4 [B(OH) 2 ] 2 } and hexahydroxytrip...
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