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El silicio5/15/2023 Several groups of samples prepared at etching current density Ia= 25 mA/cm2 and different etching times ta (from 1 up to 60 minutes) were investigated. The porous layers were obtained by electrochemical etching in a solution: HF: H2O: C2H5OH (1:1:2). The PSi samples were prepared from p-type, B-doped, (100) oriented silicon wafers with 1.0-10.0 *cm resistivity. In this paper photoluminescence, infrared (IR) absorption, ultra-soft X-ray emission spectroscopy (USXES) and atomic force microscopy (AFM) researches were used to study the reasons of different luminescence bands appearance in red spectral range for PSi samples, prepared at different anodization conditions. This suggests that combined investigations of the PSi surface morphology by AFM and PL peculiarities should be promising. Moreover it was discovered that in PSi only the upper surface layer is highly luminescent. But there are many examples of high PL intensity in PSi with very low porosity, like 10% or 22%. The nature of last two bands still under the discussion.įurthermore, it has been proposed early that only in PSi with a high level of porosity (70-80%) the strong PL could be expected. The vacuum storage research gave the evidence to assign the PL band hnm= 1.50-1.70 eV to emission of Si-Hx or hydroxyl-related species on Si crystallite surface, which can be disorbed in vacuum. The last fact indicates that these PL bands connect with the radiative transitions between localised states. The shape of elementary bands is as a rule symmetric Gaussian type. The relative intensities of elementary PL bands change with the variation of PSi preparation conditions, temperature of PL measurement, PL excitation light wavelength, as well as during aging processes in ambient air or in vacuum. The variation of maximum positions depends on PSi samples used. Recent investigations have shown that red PL band is complex and can be decomposed on two or three elementary PL bands peaked at hnm= 1.50-1.70 eV, 1.70-1.90 eV and 1.90-2.10 eV. However the detailed physical mechanism of the red PSi luminescence still remains unknown. The mechanisms connected with the emission of excitons at the Si/SiO2 interface or some oxide related species on the Si wire surface have been suggested as well. This band was explained either as related to the size distribution of quantum confined nanocrystals or as a result of emission of different types of radiative centres on Si wire surface, like: silicon clusters, polysilan complexes, siloxene molecules and defects in silicon oxide. Since this discovery numerous characterisation techniques have been used to elucidate the PL mechanism and more than 1000 articles were published concerning this effect during last 10 years. The intensive and broad "Red" (~600-800 nm) photoluminescence (PL) band in porous silicon (PSi) was discovered in 1990. Palabras claves: Silicio Poroso: PSi Fotoluminiscencia PL, Microscopía de Fuerza Atómica AFM, Espectroscopía de Emisión de Rayos-X Suaves: USXES Absorción Infrarroja: IR absorption. Los mecanismos de la transición radiativa de ambas bandas elementales son también discutidos Métodos de fotoluminiscencia, espectroscopía de emisión de rayos-X suaves, absorción infrarroja y microscopía de fuerza atómica fueron empleados para estudiar el comportamiento de ambas bandas en el espectro de fotoluminiscencia del silicio poroso, que fue preparado a diferentes condiciones de anodizado electroquímico. Se ha demostrado que la ancha e intensa banda "roja" de fotoluminiscencia en el silicio poroso no es elemental y puede estar compuesta por al menos dos bandas elementales. Keywords: Porous Silicon: PSi Photoluminiscence: PL Atomic Force Microscopy: AFM Ultra-soft X-ray emission spectroscopy: USXES Infrared absorption: IR absorption. The mechanisms of radiative transition for both elementary bands have been discussed as well. Photoluminescence, ultra-soft X-ray emission spectroscopy, infrared absorption and Atomic Force Microscopy methods were used to study the reasons of both luminescence band appearance in porous silicon photoluminescence spectra, prepared at different electrochemical etching conditions. Universidad Autónoma Metropolitana, Unidad Azcapotzalco, 02200, México D.F.E-mail: has been shown that intensive and broad "red" photoluminescence band in porous silicon is non-elementary one and could be decomposed on at least three elementary bands. Garfias 2ġ.Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, 07738, Mexico D.F.Ģ. ON MORPHOLOGY AND SILICON OXIDE COMPOSITION ON Si SURFACE OPTICAL PHENOMENA IN Si LOW-DIMENSIONAL STRUCTURES DEPENDENT
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