Issues

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2019

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vol. 17 / 

Issue 3

 



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V. A. Odarych, L. V. Poperenko, I. V. Yurgelevych
«Features of the Structure and Optical Properties of the Subsurface Layer of Porous Silicon»
0507–0518 (2019)

PACS numbers: 07.60.Fs, 78.20.Ci, 78.67.Rb, 81.05.Cy, 81.40.Tv, 81.70.Fy

Measurements of ellipsometric parameters of light reflected from the surface of the porous silicon sample, namely, the phase difference ? between the p- and s-components of the electric wave vector as well as an arctangent of the ratio of the reflection coefficients in the p- and s-planes of the sample, ?, are performed. The measurements are made within the wide interval of the light incidence angles of 46–80? at the light wavelength of 632.8 nm. The sample of porous silicon in the form of a plate of about 1 mm thickness is obtained by electrochemical etching for 3 minutes at a current density of 10 mA/cm2 of p-type monocrystalline silicon in an electrolyte HF???acetone in a ratio of volume fractions 2:1. The porous silicon plate is presented in air during more than two years. On surface of the sample, the bright interference pattern in the form of several multicolour stripes is visually observed. To determine the parameters of the reflecting system, a package of automated programs operating with ellipsometric parameters cos? and tg? is used. The obtained angle dependences of ellipsometric parameters are qualitatively described by a two-layer model of a surface film with the thickness of about 140 nm. The outer layer of film has a lower refractive index (approximately 1.33) than the inner one (1.6) adjacent to the porous silicon. By bringing the film into contact with isopropyl alcohol, it is shown that the film along its thickness has some empty pores of nanometre sizes, which can be filled by a liquid. In the process of the alcohol penetrating to the pores, the refractive index of the layers changes and, accordingly, the ellipsometric curves change radically. As found, the tg? parameter is particularly sensitive to the presence of a liquid. This parameter is equal to the ratio of the reflection coefficients in the p- and s-planes of the sample and can reach large values due to the penetration of the alcohol into the film. Based on the experimental evidence obtained, it is proposed to create polarization sensors and linear polarizers, which use such-type porous silicon.

Keywords: porous silicon, film, refractive index, ellipsometry, linear polarization

https://doi.org/10.15407/nnn.17.03.507

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This article is licensed under the Creative Commons Attribution-NoDerivatives 4.0 International License
© NANOSISTEMI, NANOMATERIALI, NANOTEHNOLOGII G. V. Kurdyumov Institute for Metal Physics of the National Academy of Sciences of Ukraine, 2019
© V. A. Odarych, L. V. Poperenko, I. V. Yurgelevych, 2019

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