Correlation of diffuse scattering with nanocrystallite size in porous silicon using transmission microscopy

We use high resolution cross sectional transmission electron microscopy to image the nanostructure of (100) p-type porous Si. A network of pore tracks subdivide the material into nano-islands and nanocrystallites are resolved throughout the material. With distance from the substrate, electron diffraction develops noncrystalline-like diffuse patterns that dominate the coherent scattering in the topmost luminescent layer. Also, with distance from the substrate, crystalline islands evolve such that their size drops to as small as 1 nm in the topmost luminescence material. Although the topmost luminescent layer is very rich in nanocrystallites, it has the strongest diffuse scattering of all regions. This confirms that diffuse scattering is due to size reduction effects rather than to an amorphous state.