Angular Ellipsometry of Porous Silicon Surface Layers

Authors L.V. Poperenko , S.G. Rozouvan, I.V. Yurgelevych , P.O. Lishchuk

Taras Shevchenko National University of Kyiv, 64/13, Volodymyrska St., 01601 Kyiv, Ukraine

Issue Volume 12, Year 2020, Number 3
Dates Received 03 February 2020; revised manuscript received 15 June 2020; published online 25 June 2020
Citation L.V. Poperenko, S.G. Rozouvan, I.V. Yurgelevych, P.O. Lishchuk, J. Nano- Electron. Phys. 12 No 3, 03024 (2020)
PACS Number(s) 78.68. + m, 81.05.Rm
Keywords Porous silicon (3) , Optical properties (22) , Oxidation (4) , Film (136) , Ellipsometry (5) .

An ellipsometric diagnostics of porous silicon samples with different degree of porosity P was carried out. The porous silicon samples with degree of porosity of 30 % and 60 % were fabricated on (100) silicon wafers of p-type conductivity with a high concentration of boron dopant by etching in solution of HF and ethanol. To characterize the optical properties of porous silicon samples the angular dependences of such ellipsometric parameters as D (cosD) and Y (tgY) were measured within a wide range of light incidence angles. Due to their angular dependences the principal angle jp of light incidence and a value of tgYmin and its angular position were determined. The optical properties of the samples of porous silicon with different degree of porosity after keeping in isopropyl alcohol during one day were also studied. The morphology of the porous silicon surface was investigated by atomic force microscopy. It was found that the ellipsometric parameters are significantly different for these two samples of porous silicon with different degree of porosity P, namely the differences in the value of the principal angle of light incidence and the angular position of the tgY minimum are about 10°. In the framework of the model of the effective medium the obtained result was explained by the presence in porous silicon sample with P = 60 % of larger amount of a substance with small refractive index, namely air and silicon oxide formed on the walls of its pores. It was established that treatment of the samples of porous silicon in isopropyl alcohol during one day and subsequent keeping of samples in air atmosphere leads to a decrease in the principal angle of light incidence and refractive index due to porous silicon oxidation.

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