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We study the effect of substrate induced strain on the structural, transport, optical, and electronic properties of Sr 2 CoNbO 6 double perovskite thin films. The reciprocal space mapping, ϕ -scan, and high-resolution θ –2 θ scans of x-ray diffraction patterns suggest the epitaxial nature and high-quality of the films deposited on various single crystal ceramic substrates. A systematic enhancement in the dc electronic conductivity is observed with an increase in the compressive strain while there is a sharp reduction in the case of tensile strain, which is further supported by a change in the activation energy and the density of states near the Fermi level. The optical bandgap extracted from two distinct absorption bands, observed in the visible–near infrared spectroscopy, shows a non-monotonic behavior in the case of compressive strain while there is significant enhancement with tensile strain. Unlike the bulk Sr 2 CoNbO 6 (Co 3 + and Nb 5 + ), we observe different valence states of Co, namely, 2+, 3+, and 4+, and tetravalent Nb (4 d 1) in the x-ray photoemission spectroscopy measurements. Moreover, a reduction in the average oxygen valency with the compressive strain due to enhancement in the covalent character of Co/Nb–O bond is evident. Interestingly, we observe sharp Raman active modes in these thin films, which indicates a significant enhancement in structural ordering as compared to the bulk. [ABSTRACT FROM AUTHOR]

Presents a study which examined the structure of thin films of amorphous chalcogenide and bulk alloys deposited at various angles of incidence and the photostructural changes occurring therein on illumination with ultraviolet light using far-infrared spectroscopy and x-ray photoelectron spectroscopy. Magnitude of the photostructural changes; Influence of the composition and structural units on the photostructural changes; Changes in the band intensities.