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

Abstract

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)

Study of electronic structure and phase composition of porous silicon

“…A phase of low coordinated silicon Si (a more ordered system compared to Si-Ar and a Si : H) dominates in a deeper layer (60 nm), a "phase" of crystalline silicon (possibly in the form of nanocrystals) appears, the fraction of SiO 2 decreases, and the contribution of oxide SiO x disappears (Table 2), i.e., the surface of a sample is more disordered and oxidized as compared with a deeper layer. This result agrees well with our previous studies [5][6][7][8][9]. …”

“…Gaseous molecules from air can sorb at the surface of porous silicon and undesirable impurities from the substrate can bind there into neutral compounds. The phase composition of the surface differs depending on conditions of production and storing, as well as on storage duration [5][6][7][8][9], therefore, the factors men tioned should be taken into account by developing device structures based on porous silicon. Stabiliza tion of porous silicon characteristics, or their control lable variation in storage, allows us to apply porous sil icon as a material for developing filters, molecular meshes, chemical separators, catalyst carriers, and reactors to carry out chemical reactions in nanovol umes [10].…”

Ultrathin nano-sized Al2O3 strips on the surface of por-Si

“…The thickness of the porous layer was about 200 nm, the average pore size was less than 5 nm. Technology of obtaining of the nanoporous silicon with the mean size of pores less than 5 nm was worked out previously and described in details in our works [6,24]. In order to perform a comparative analysis of the structural and optical properties under similar growth conditions, we obtained Al 2 O 3 film grown on the original (unetched) plate of monocrystalline Si (111).…”

Investigations of nanodimensional Al2O3 films deposited by ion-plasma sputtering onto porous silicon

“…We obtained a porous silicon layer in the structure by the method of the electrochemical etching of single crys talline silicon wafers of the (111) orientation with a wafer resistivity of 10 Ω cm in an alcohol solution of fluoric acid by the conventional technique [6,17]. The porous layer thickness amounted to about 200 nm.…”