Influence of the current density and resistivity on the optical properties of p-type porous silicon thin films fabricated by the electrochemical anodizing method
Abstract:Porous Silicon thin films were produced in this work by the electrochemical anodizing method. The samples were fabricated anodizing p type Si substrates with different resistivities in hydrofluoric acid. Samples were prepared at different current densities. The films were characterized through reflectance and room photoluminescence (PL) measurements in the visible region. A simple theoretical model is proposed to calculate the Optical constants of the material using a theoretical simulation of the reflectance … Show more
“…Thus, the observed optical anisotropy of the porous silicon surfaces is not unexpected. As to the values of the obtained refractive indices, similar results were reported in refs − .…”
Infrared spectroscopic ellipsometry (IRSE) was applied for characterization of porous silicon (PSi) electrochemically prepared in acidic fluoride solution. When no formation of SiO2 was involved in the preparation, an anisotropic distribution of PSi bonds with the terminating molecules was achieved. On the contrary, oxidation of PSi samples during the preparation led to an isotropic structure. IR spectra obtained from organically functionalized PSi surfaces suggested that the morphology of the organic layer on PSi was anisotropic for electrochemical grafting of methyl but not nitrobenzene. Comparison between the IRSE spectra obtained from PSi and Si(111) surfaces and application of optical models supported these observations.
“…Thus, the observed optical anisotropy of the porous silicon surfaces is not unexpected. As to the values of the obtained refractive indices, similar results were reported in refs − .…”
Infrared spectroscopic ellipsometry (IRSE) was applied for characterization of porous silicon (PSi) electrochemically prepared in acidic fluoride solution. When no formation of SiO2 was involved in the preparation, an anisotropic distribution of PSi bonds with the terminating molecules was achieved. On the contrary, oxidation of PSi samples during the preparation led to an isotropic structure. IR spectra obtained from organically functionalized PSi surfaces suggested that the morphology of the organic layer on PSi was anisotropic for electrochemical grafting of methyl but not nitrobenzene. Comparison between the IRSE spectra obtained from PSi and Si(111) surfaces and application of optical models supported these observations.
“…Etch rate increases with current density, since a higher current density provides an increase in the number of charge carriers, and thereby the rate of charge exchange across the interface. The mechanisms on the PL of PS films are still in debate [3][4][5][6][7][8][9][10]. It is safe to conclude at this stage that the PL spectrum of the anodized PS films is independent on the anodization current density for our p-type silicon.…”
Section: Resultsmentioning
confidence: 87%
“…For example, Ohmukai et al observed that both the peak wavelength of the photoluminescence (PL) and the size of the silicon nanocrystals evolve with the anodization current density in the range of 2-100 mA/cm 2 [2]. Torres et al studied the influence of the current density on the PL properties of p-type PS films fabricated by the electrochemical anodizing method [3]. They reported the peak wavelength of the PL spectra of samples prepared on 0.01 Ω⋅cm substrates, at different anodizing currents, are shifted toward shorter wavelengths as the anodizing current increases.…”
Porous silicon (PS) is usually prepared by means of the anodization under constant current density, and fabrication of PS is a key step towards the realization of all-silicon electronic devices. It is a general belief that the photoluminescent properties of electrochemically etched PS depend on the anodization current density. In this work, we electrochemically prepared a series of PS films in the electrolyte of hydrofluoric acid by varying anodizing current density in the range of 1-70 mA/cm2. In spite of the different anodizing current density, the peak wavelength of the photoluminescence spectrum of the electrochemically anodized PS does not depend on the anodization current density. SEM has been utilized to characterize the morphology of the prepared PS films, and the mechanism is discussed for the anodization current independent photoluminescence of PS.
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