Nanocomposites and nanomaterials

Charge transportation in porous silicon/graphene-based nanostructures 
I. Olenych1, L. Monastyrskii1, O. Aksimentyeva1, L. Orovcík2
1 Ivan Franko National University of Lviv, 50 Dragomanov Str., Lviv-79005, Ukraine. E-mail: iolenych@gmail.com
2 Institute of Materials and Machine Mechanics Slovak Academy of Sciences, Dubravska cesta 9, 845 13 Bratislava, Slovak Republic

Porous silicon (PS) nanostructures exhibit specific structural features that ensure large absorbing surface and outstanding optical and luminescent properties. In recent years, there has been growing interest in combining PS with graphene-based materials, including graphene oxide (GO) and reduced graphene oxide (RGO). Some previous researches have shown the usefulness of the hybrid structures for their application in photonic and energy conversion devices [1, 2]. In such structures, graphene not only serves as a flexible transparent electrode but also participates in separation and transportation of charge carriers. Research on electrical properties of the PS/graphene-based structures provides a great platform for the potential opportunities in many fields ranging from optoelectronics to power engineering and sensing applications. 
In this work, the PS/GO and PS/RGO nanostructures are designed in order to investigate their electrical and gas sensing properties. Obtained nanomaterials were characterized by scanning electron microscopy. We analyzed temperature dependencies of the electrical conductivity for the PS/graphene-based structures within the model of disordered semiconductors and determined the activation energy of charge transportation. Based on the spectra of thermally stimulated depolarization current, the localized electron states in such structures were found. By means of impedance spectroscopy, we determined the internal resistance of the hybrid structures and revealed the significant influence of the surrounding atmosphere on their electrical parameters. The results obtained in the present investigation would allow the creation of effective gas sensors. 

1.	Olenych I.B., Aksimentyeva O.I., Monastyrskii L.S., Horbenko Yu.Yu., Partyka M.V. Electrical and Photoelectrical Properties of Reduced Graphene Oxide-Porous Silicon Nanostructures // Nanoscale Res Lett.-2017.-12.-272. 
2.	Oakes L., Westover A., Mares J.W., Chatterjee S., Erwin W., Bardhan R., Weiss S.M., Pint C.L. Surface engineered porous silicon for stable, high performance electrochemical supercapacitors // Sci Reports.-2013.-3.-3020.