Crystalline phase transformation in silicon nanowires from cubic diamond to hexagonal diamond under strong laser excitation, caused by inhomogeneous heating-induced mechanical stresses.

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Raman spectroscopy is used to probe free charge carriers in layers of silicon nanowires (SiNWs) formed by metal‐assisted chemical etching of crystalline silicon (c‐Si) wafers followed by additional doping with boron. One‐phonon Raman spectra of the boron‐doped SiNWs are strongly modified due to the Fano effect that allowed us to determine the free carrier concentration in the nanowires in the range from 1019 to 1020 cm−3, depending on the doping conditions. The micro‐Raman mapping was used to determine the depth profile of charge carrier density along nanowires, which decreases toward the SiNWs/c‐Si interface. The obtained results are discussed in view of possible applications of the Raman spectroscopy for express‐diagnostics of doped Si nanostructures for photonics and thermoelectric applications.

Infrared spectroscopy in attenuated total reflection (ATR) mode is used to evaluate the concentration of free charge carriers (electrons) in n‐type macroporous silicon (Si) layers formed by metal‐assisted chemical etching of crystalline silicon (c‐Si) followed by additional doping with phosphorus. The ATR spectra are fitted by considering an effective medium approximation and Drude model, which is modified to describe an additional scattering of the charge carriers on the surface of Si nanocrystals. The electron concentration is of the order of 1019 cm−3 and it is slightly dependent on the layer thickness, while the surface scattering of charge carriers increases with layer thickness. The obtained results are discussed in view of possible applications of the ATR method for an express diagnostics of doping efficiency of Si nano‐ and microstructures for photonic and thermoelectrical applications.

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The impact of free charge carriers in arrays of silicon nanowires (SiNWs) of p‐ and n‐type conductivities on their optical properties is probed by means of the infrared spectroscopy in attenuated total reflectance mode (IR‐ATR) and Raman scattering. SiNWs are fabricated by metal‐assisted chemical etching of low‐doped p‐type crystalline silicon (c‐Si) wafers followed by thermodiffusional doping with p‐ and n‐type impurities. The free charge carrier concentration in SiNWs is determined from their ATR spectra fitted using a model of the anisotropic effective medium with free charge carriers. The obtained data on the free charge carrier concentrations in the range of 1019–1020 cm−3 are compared with the corresponding values obtained from the Raman spectra, which are analyzed by considering the Fano effect in SiNWs, and the results of both methods are used to evaluate the electrical properties of SiNWs. The proposed optical methods to probe the electrical properties of SiNWs are discussed in view of possible applications in nanoelectronics and thermoelectric devices.

Silicon nanowires obtained by metal-assisted chemical etching of crystalline silicon (Si) wafers are studied by Raman spectroscopy to reveal the effect of the formation time of nanowires and their additional doping with boron and phosphorus. The observed modification of the spectrum shape in the boron-doped samples due to the Fano effect made it possible to estimate the concentration of free holes in Si nanowires, which is of the order of 1019 - 1020 cm3, depending on the preparation conditions. The obtained results indicate the potential of the Raman spectroscopy for contactless diagnostics of Si nanostructures.