Electron structure of porous silicon obtained without the use of HF acid

Reproducible technique for obtaining of porous silicon samples without the use of fluoric acid was elaborated. The main component for electrochemical etching of silicon is a concentrated aqueous solution of NH4F. The obtained samples are characterized by unusual pore morphology and the presence of corrugated “nanoribbons” of Si on the surface of porous layer. The density of occupied electron states in the samples determined by ultrasoft X‐ray emission spectroscopy shows practically complete absence of Si‐O bonds in the near‐surface layers of porous silicon (por‐Si). Analysis of the data of X‐ray absorption spectra and X‐ray photoelectron spectra demonstrates the presence of a great amount of Si‐O bonds just on the surface of the sample and an unusual abrupt decay in the absorption spectra near Si L2,3 edge of elementary silicon. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)