Thermodynamic pathway for the formation of SnSe and SnSe sub(2) polycrystalline thin films by selenization of metal precursors

In this work, tin selenide thin films (SnSe sub(x)) were grown on soda lime glass substrates by selenization of dc magnetron sputtered Sn metallic precursors. Selenization was performed at maximum temperatures in the range 300 degree C to 570 degree C. The thickness and the composition of the films...

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Bibliographic Details
Published in:CrystEngComm 2013-11, Vol.15 (47), p.10278-10286
Main Authors: Fernandes, P A, Sousa, M G, Salome, PMP, Leitao, J P, da Cunha, AF
Format: Article
Language:English
Subjects:
Direct current
Energy gap
Glass
Precursors
Reflectance
Thin films
Tin
X-rays
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Summary:In this work, tin selenide thin films (SnSe sub(x)) were grown on soda lime glass substrates by selenization of dc magnetron sputtered Sn metallic precursors. Selenization was performed at maximum temperatures in the range 300 degree C to 570 degree C. The thickness and the composition of the films were analysed using step profilometry and energy dispersive spectroscopy, respectively. The films were structurally and optically investigated by X-ray diffraction, Raman spectroscopy and optical transmittance and reflectance measurements. X-Ray diffraction patterns suggest that for temperatures between 300 degree C and 470 degree C, the films are composed of the hexagonal-SnSe sub(2) phase. By increasing the temperature, the films selenized at maximum temperatures of 530 degree C and 570 degree C show orthorhombic-SnSe as the dominant phase with a preferential crystal orientation along the (400) crystallographic plane. Raman scattering analysis allowed the assignment of peaks at 119 cm super(-1) and 185 cm super(-1) to the hexagonal-SnSe sub(2) phase and those at 108 cm super(-1), 130 cm super(-1) and 150 cm super(-1) to the orthorhombic-SnSe phase. All samples presented traces of condensed amorphous Se with a characteristic Raman peak located at 255 cm super(-1). From optical measurements, the estimated band gap energies for hexagonal-SnSe sub(2) were close to 0.9 eV and 1.7 eV for indirect forbidden and direct transitions, respectively. The samples with the dominant orthorhombic-SnSe phase presented estimated band gap energies of 0.95 eV and 1.15 eV for indirect allowed and direct allowed transitions, respectively.
ISSN:1466-8033
DOI:10.1039/c3ce41537f