On the basis of absorption spectroscopy data the temperature evolution of Cu 2+ ion environment in the layered compound (C 2 H 5 NH 3 ) 2 CuCl 4 was studied within the temperature range of 4.5 -310 K. For the detailed analysis of the experimental data the specially created program package Crys Tool 1.0 based on the quantum mechanical models first of all on the model of normalised spherical harmonics (NSH) was used. It has been found that the crystal structure in the low temperature phases contains tetragonally distorted octahedral metal -halogen complexes. The parameters of crystal field, normalised spherical harmonics, angular overlap model as well as the metal -halogen distances show anomalous behaviour at the points of phase transitions: T c = 10 K and T 4 = 232 K (for heating). The changes of these parameters observed around T 5 = 65 K also may be related to previously unknown phase transition.

We studied an effect of the graphene oxide (GO) layer on the optical and electrical properties of porous silicon (PS) in hybrid PS–GO structure created by electrochemical etching of silicon wafer and deposition of GO from water dispersion on PS. With the help of scanning electron microscopy (SEM), atomic-force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy, it was established that GO formed a thin film on the PS surface and is partly embedded in the pores of PS. A comparative analysis of the FTIR spectra for the PS and PS–GO structures confirms the passivation of the PS surface by the GO film. This film has a sufficient transparency for excitation and emission of photoluminescence (PL). Moreover, GO modifies PL spectrum of PS, shifting the PL maximum by 25 nm towards lower energies. GO deposition on the surface of the porous silicon leads to the change in the electrical parameters of PS in AC and DC modes. By means of current–voltage characteristics (CVC) and impedance spectroscopy, it is shown that the impact of GO on electrical characteristics of PS manifests in reduced capacitance and lower internal resistance of hybrid structures.

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We studied an effect of the graphene oxide (GO) layer on the optical and electrical properties of porous silicon (PS) in hybrid PS-GO structure created by electrochemical etching of silicon wafer and deposition of GO from water dispersion on PS. With the help of scanning electron microscopy (SEM), atomic-force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy, it was established that GO formed a thin film on the PS surface and is partly embedded in the pores of PS. A comparative analysis of the FTIR spectra for the PS and PS-GO structures confirms the passivation of the PS surface by the GO film. This film has a sufficient transparency for excitation and emission of photoluminescence (PL). Moreover, GO modifies PL spectrum of PS, shifting the PL maximum by 25 nm towards lower energies. GO deposition on the surface of the porous silicon leads to the change in the electrical parameters of PS in AC and DC modes. By means of current-voltage characteristics (CVC) and impedance spectroscopy, it is shown that the impact of GO on electrical characteristics of PS manifests in reduced capacitance and lower internal resistance of hybrid structures.

In this work, the hybrid structures were created by electrochemical etching of silicon wafer and deposition of reduced graphene oxide (RGO) on the porous silicon (PS) layer. With the help of SEM and AFM, the formation of hybrid PS–RGO structure was confirmed. By means of current–voltage characteristic analysis and impedance spectroscopy, we studied electrical characteristics of PS–RGO structures. The formation of photosensitive electrical barriers in hybrid structures was revealed. Temporal parameters and spectral characteristics of photoresponse in the 400–1100-nm wavelength range were investigated. The widening of spectral range of photosensitivity of the hybrid structures in short-wavelength range in comparison with single-crystal silicon was revealed. The obtained results broaden the prospects of application of the PS–RGO structures in photoelectronics.