PHOTOSENSITIVE STRUCTURES BASED ON THE SILVER-DOPED POROUS SILICON AND REDUCED GRAPHENE OXIDE

Background. The synergistic combination of useful properties of the different nature nanostructures in composites is one of the main methods of improving the functionality of nanomaterials. In particular, due to the unique properties of graphene as well as the large absorbing surface area and the low reflectance of porous silicon (PS), hybrid structures based on them are promising for photoelectric applications. Therefore, the possibility of increasing the photosensitivity of such structures by electrochemical introduction of silver nanoparticles into the porous layer was studied. Materials and Methods. Nanostructured layers of the PS obtained by electrochemical etching of a silicon wafer and a film-forming suspension of reduced graphene oxide (RGO), which was deposited on the porous layer surface, were used to create photosensitive structures. The resulting structures with silver incorporated into the PS were explored using scanning electron microscopy. The electrical and photoelectric properties of the hybrid structures were studied based on the analysis of I-V characteristics and impedance frequency dependencies measured in the dark and under irradiation with white light. Results and Discussion. It has been established that silver is deposited mainly in the surface layer of the PS and its amount depends on the duration of electrochemical introduction. Doping the porous layer with silver increases the electrical conductivity and capacitance of the PS–RGO structures. Irradiation of the surface of experimental structures with white light causes an increase in the forward and reverse current through the structures but has almost no effect on the lateral I-V characteristics due to shunting the RGO film by silver nanoparticles. Based on the analysis of impedance spectra in the 102–105 Hz frequency range, the effect of irradiation on the resistive-capacitive properties of hybrid structures was studied. Conclusion. It was established that the incorporated silver forms additional current paths through the PS. The RGO film resistance is partially shunted by the silver nanoparticles as well. As a result, the obtained structures demonstrate an increase in conductivity both when the charge is transferred through the structure and along the surface. In addition, silver nanoparticles contribute to the accumulation of photogenerated charge carriers and their extraction from the PS.