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Background and Objectives: Porous silicon nanowires (SiNP) obtained by the method of metal stimulated chemical etching (EE method) are of great interest. The physical properties of this material depend significantly on the morphology of the nanostructures and their sizes. Given in the literature data on the effect of small doses of ionizing radiation on metals and alloys and the effect of irradiation on the properties of porous silicon and SiNP, makes sense to modify not only the substrate, but also the SiNP layer during its formation by irradiation. A change in the morphology of the formed layers with increasing in situ irradiation within small doses can affect the properties of SiNP. In the literature known to us, this issue is not considered. This work presents studies of the total reflection, Raman scattering, and photoluminescence of SiNP upon irradiation with γ-rays directly in the production process (in situ). Materials and Methods: The formation of nanoporous silicon structures was performed on non-irradiated and irradiated with small doses of gamma-quanta substrates. The substrates were processed by the Saratov State University’s betatron electron brake accelerator at a maximum energy of Eymax ~ 25 MeV. The radiation dose was 30 and 40 kR. A layer of porous SiNP nanosilicon was formed on irradiated and non-irradiated substrates. Samples were obtained by water-based non-electric etching or metal-stimulated chemical etching. The method of chemical etching EE is based on the replacement of silicon when reducing Ag+ → Agо on the surface of the silicon substrate using Ag in an aqueous solution of AgNO3. Porous silicon structures were formed by a two-stage method on irradiated gamma-quanta and non-irradiated p-type silicon substrates with a resistivity of 4.5 Ω cm, oriented in the plane . The substrate was lowered into an aqueous solution of 0.01 M AgNO3 and 5M HF for 60 s., then was etched in an aqueous solution of 5M HF, 0.5 M H2O2 for 20, 40 and 60 minutes, respectively. The studied nanoporous structures were obtained on irradiated and non-irradiated substrates without irradiation and when irradiated in situ with inhibitory gamma radiation of the medical linear electron accelerator Varian Unique of State Health Institution “Regional Clinical Oncology Dispensary” at an electron energy of 6 MeV. After receiving the samples, they were purified in concentrated nitric acid for an hour. The structural properties of SiNP were studied using measurements on an analytical complex based on the Mira 2 LMU scanning electron microscope, as well as the DRON-4 diffractometer using an x-ray tube with a copper anode (Cu-Ka). Full reflection spectra in the range of 500–1100 nm were obtained using a LOMO SF-56 spectrophotometer equipped with a special integrating set-top box. Raman spectra were recorded using a Renishaw inVia spectrometer. Results: The samples under study are quasiordered ensembles of silicon nanowires oriented almost normal to the substrate. The thickness of the SiNP layer is of the order of 1–8 μm, depending on the preparation conditions, and the diameter of the nanowires was 30–400 nm. In all SiNP samples, a decrease in total reflection was observed in the wavelength range of 400–1000 nm as compared to a single-crystal substrate, which is associated with light scattering on an inhomogeneous structural surface. At the initial stage of the process, the defective state of the substrate was decisive; microstresses on the substrate disappear when it is irradiated. For SiNP samples, total reflection increased with increasing radiation dose over time (from 0 to 24 kR) due to improved surface quality, reduced scattering, and a change in layer thickness. In addition, in situ monitoring of SiNP samples indicates the influence of not only the radiation dose of the formed layer on the reflection value, but also the dose of preliminary irradiation of the substrate. Raman spectra were studied to determine the effect of gamma-irradiation on the properties of porous silicon – SiNP in situ. The intensity of the main peak of Raman scattering of SiNP samples obtained on non-irradiated and irradiated substrates is significantly higher compared to the intensity of the main peak characteristic of single-crystal silicon. Against the background of the high Raman signal, light scattering from particles with broken bonds does not appear and basically gives a maximum – a peak P1 of the order of 519.5 cm-1, slightly shifted to the low-frequency region relative to the maximum of peak P1 of a single-crystal silicon substrate 520 cm-1. An increase in the irradiation dose of the substrate leads to an increase in the intensity of the main Raman peak. Studies of Raman spectroscopy of nanostructured porous silicon-silver layers have revealed the effect of surface giant signal amplification (SERS). The maximum silver content is below the surface of the samples. The depth of the silver-enriched layer is about 250– 400 nm. The photoluminescence peak of SiNP samples formed on irradiated and non- irradiated substrates shifts to the shortwavelength region as the radiation dose increases. The shift is much more dependent on the dose of the substrate than on the irradiation of the layer. The calculated nanocrystallite size by λmax was about 2 nm. Conclusion: The results of an experimental study of the optical properties of porous Si structures obtained by metal-stimulated chemical etching when irradiated with small doses of gamma-quanta directly during in situ formation are presented. In situ monitoring of samples indicates the influence not only of the radiation dose of the resulting layer on the value of total reflection, but also the dose of pre-irradiation of the substrate. Studies of Raman spectroscopy of nanostructured layers of “porous silicon-silver” revealed the effect of surface giant signal amplification in samples. There is a shift in the wavelength of the maximum photoluminescence from 600 nm to 750 nm when the irradiation of the substrate changes from 0 to 40 kR at the same radiation dose of the layer.

The results of a study of the optical properties of porous silicon nanostructures obtained by metal-assisted chemical etching of γ-quanta irradiated with low doses during their formation are discussed. The total reflection from the obtained samples depends not only on the irradiation dose of the forming layer, but also on the dose of preliminary irradiation of the initial silicon wafer by in situ control. By studying the Raman spectra of the samples, it was confirmed that changes in the spectra take place both due to the effect of small doses of γ-quanta on the initial silicon wafers and due to the in situ effect of gamma radiation on the forming SiNWs. We observed a shift in the wavelength of the photoluminescence maximum from 600 nm to 750 nm with a change in the irradiation of the initial silicon wafer from 0 to 40 kR at the same dose of irradiation of the forming porous layer.

Photoluminescent macroporous silicon is studied for tumor imaging application. Gamma-radiation is used for modification of morphology of pores and their size. It is shown by Raman and photoluminescence study that after the irradiation of gamma rays new nanocrystallites of smaller diameter in comparison to the initial porous silicon appeared.

The possibility of modifying the photoluminescence properties of porous silicon by irradiation with low doses of γ photons from a 226Ra radioisotope source and bremsstrahlung is demonstrated. The position of the longest photoluminescence wavelength tends to shift to the short-wavelength region of the spectrum. The emission efficiency increases upon irradiation of both the substrate and the layer formed.

The study of the formation of silicon nanowhiskers by the method of non-current two-step etching is presented in this paper. Silicon nanowhiskers were obtained on unirradiated single-crystal silicon and on irradiated γ-quantum substrates. At an etching time of 20 to 50 minutes, the length of nanowhiskers is independent of the radiation dose (with a diameter of 70 to 140 nm), however, with increasing etching time, the length of the nanowhiskers increases sharply with increasing radiation dose. The optical and structural properties of silicon nanowhiskers under the influence of gamma irradiation are discussed.

Experimental studies were carried out by two different sources of gamma quanta. Samples were irradiated gamma - quantum radioisotope source 226Ra and electron accelerator braking gamma radiation - betatron Saratov state university. The form of the diffractograms shows the high crystallinity of the samples under study. The effect of gamma rays of radium led to a slight shift of the maximum of the reflex relative to the angle 2θ=29.18° to the left and a decrease in its width. The structure of the samples irradiated with γ-quanta of the bremsstrahlung of the betatron, according to the measurements, has undergone more significant and unexpected changes.

The possibilities of modifying the IR spectra of porous silicon under irradiation by low doses of gamma — quanta of radioisotope source of 226Ra and bremsstrahlung radiation are investigated.

The possibility of multiparametric determination of properties of structures from the data on the dependence of reflectances Rp and Rs for polarized radiation and ratio Rp/Rs on the angle of incidence θ and from the angular dependence 1/Rp(ΔR/Δθ) is investigated. The results of natural and computer experiments revealed a high sensitivity of the angular dependence Rp(θ) of the reflectance to the values of optical constants and thickness of layered structures. Quantitative results of multiparametric measurements are verified by the independent method of spectral ellipsometry. The possibility of multiparametric determination of the properties and thickness of nanometer dielectric, metallic, and semiconducting layers on various substrates and the properties of substrates in such structures is established.

The results of numerical simulation of a nanodimensional film-transition layer-absorbing substrate structure are presented. It is found that the transition layer affects the accuracy of determining the refractive index and thickness of the nanodimensional coating. It is shown that the introduction of the effective values of the refractive index and absorption coefficient of the substrate improves the accuracy of ellipsometric measurements of the nanodimensional film parameters. Physical (full-scale) and numerical experiments demonstrate that, when the thickness and refractive index of a nanodimensional film on a substrate with an unknown transition layer comparable in thickness with the film are measured, it is appropriate to replace the substrate-transition layer structure by a substrate with effective optical parameters. It is found that a change in the thickness of the transition layer does not noticeably affect the accuracy of determining the thickness and refractive index of the film deposited when the effective values of the refractive index and absorption coefficient of the substrate are used.

This article deals with investigation of nanolayers' properties generated on Si surface in H 2 O

The semiclassical relationships for the complex refractive index are used to find the regions of integration of the Kramers-Kronig dispersion relation required to yield the spectral dependence of the optical properties of semiconducting materials in the vicinity of the plasma resonance of the charge carriers with a prescribed accuracy. The refractive index n and the absorption coefficientκ of heavily doped Si in the vicinity of the plasma resonance of the charge carriers are determined by the Kramers-Kronig method and by the method of two media. The values of n andκ obtained by these methods are in good agreement with values calculated on the basis of the Drude-Lorentz semiclassical theory of dispersion.