Nanostructured surfaces

Ab initio studies of the gas adsorption on the surface CdSe1-xSx ultra-thin films
Kashuba A.I.1, Semkiv I.V.1, Andriyevsky B.2, Ilchuk H.A.1, Kashuba N.Yu.1, Petrus R.Yu.1
1Lviv Polytechnic National University, 12, S. Bandera Str., Lviv-79013, Ukraine
E-mail: andrii.i.kashuba@lpnu.ua
2Koszalin University of Technology, 2, Sniadeckich Str., Koszalin 75-453, Poland

Substitutional solid-state solutions with a general formula CdSe1-xSx attract a considerable interest of researchers from both fundamental and applied viewpoints. Recently, extensive studies have been conducted which are aimed at manufacturing highly efficient CdS/CdTe solar cells, in which CdS thin films serve as a ‘wideband optical window’. Ternary CdSe1-xSx films are promising in this respect at least because they enable changing and combining basic physical characteristics of the initial binary compounds CdSe and CdS in a controlled and predictable manner.
Semiconducting compounds of AIIBVI group represent also promising materials for different sensors. In particular, they can be utilized as working elements of gas sensors. Potentials of the binary compounds CdS and CdTe as gas sensors have been analyzed, e.g., in the work [1]. This has been done for the particular cases of nanorods deposited on Ti substrates and thin films. In spite of these achievements, the main properties of the CdSe1-xSx system associated with its possible sensor applications have not yet been elucidated.
All of our calculations, including geometry optimization and calculations of total energy, energy spectra, density of states and adsorption configuration of gases, were performed with a functional density functional theory (DFT). Thin films of CdSe1-xSx were modeled on the basis of a ‘parent’ CdSe compound with wurtzite crystal structure. The electronic band structure and the main optical properties obtained theoretically in this work are compared with the experimental data known from the literature, which reveals a fair agreement with the experiment.

1.	S.T. Navale, A. T. Mane, M. A. Chougule, N. M. Shinde, JunHo Kim and V. B. Patil, Highly selective and sensitive CdS thin film sensors for detection of NO2 gas// RSC Adv., 4: 44547–44554 (2014).