Peculiarities of Electron-Energy Structure of Surface Layers of Porous Silicon Formed on p-Type Substrates

The atomic and electron structure of porous silicon surface layers were investigated by the methods of ultrasoft X-ray emission spectroscopy and X-ray absorption near edge structure spectroscopy. The thicknesses of the surface oxide layer and the degree of distortion of the silicon-oxygen tetrahedron in this layer were estimated. The thickness of the surface oxide layer lying on the amorphous layer, which covers the nanocrystals of porous silicon upon keeping for a year, exceeds severalfold the thickness of the natural oxidation of plates of monocrystalline silicon. The distortions of the silicon-oxygen tetrahedron-the main structural unit of silicon oxide-are accompanied by the strain of Si-O bonds and the increase in Si-O-Si bond angles.