Infrared characterization

of UV-oxidized porous silicon layers

S. Aouida, M. Saadoun, K. Ben Saad, M.F. Boujmil, B. Bessais*

Institut National de Recherche Scientifique et Technique, Laboratoire de Photovolta´que et des Semiconducteurs,

BP 95, 2050 Hammam- Lif, Tunisie

* Corresponding author. E-mail: brahim.bessais@inrst.rnrt.tn

Received: 20 April 2004; revised version accepted: 20 May 2005

Abstract

Porous Silicon oxidation is widely used in diverse application types. The oxidation process can strongly modify the structural and optical properties of PS. Various oxidation methods were used to passivate the huge internal PS surface. The process strongly depends on the way by which oxygen is incorporated into the porous matrix. For this purpose, we investigate the effect of oxidation based UV irradiation of the PS structure using FTIR (Fourier Transform Infrared Spectroscopy) measurements. The oxidation process behaviour was followed by recording the evolution of the IR absorption peaks of the SiHx, OySiHx, SiOx and Si-O-Si stretching modes. The infrared absorption peak of the vibrational stretching modes of silicon dioxide and silicon hydroxides and hydrides, which appear respectively in the range of 1300-1000 cm-1 and 2300-2000 cm-1, were deconvoluted into Gaussian contributions. We found that UV irradiations accelerate oxygen incorporation into the porous structure. The intensities and area of the Gaussian profile attributed to SiHx decrease with increasing the UV irradiation. The intensities and area of the OySiHx Gaussian profiles increase for the first times of UV irradiation and then decreases. These observations give an idea about the UV oxidation process. The maximum peak position of all species shift with increasing UV irradiation. This behavior was explained by the variation of the oxygen stoechiometry in the PS layers, which produce different localized vibrational modes.

Keywords: Porous silicon; Infrared spectra; UV oxidation.

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