Preparation and optical characterization of zinc selenide /plasma polymerized o-methoxyaniline hybrid thin films.

Abstract

Hybrid thin films are highly significant in a wide range of technological applications due to the corresponding properties of inorganic and organic materials. In this study, inorganic-organic hybrid thin films have been successfully fabricated through a two-step deposition process.The inorganic layer of zinc selenide (ZnSe) is deposited first through chemical bath deposition technique and the organic layer is deposited onto the inorganic layer using a capacitively coupled plasma polymerization technique. For inorganic layerZnSe has been chosen due toits high photoconductivity.On the other hand, for organic layer ortho-methoxy aniline (OMA) has been chosen, because it is a low-cost monomer and due to the presence of methoxy group in ortho position, thin films can easily be synthesized either chemically or electrochemically with higher processibility and solubility. The base ZnSe layer is deposited for one hour and plasma polymerized OMA (PPOMA) has been deposited for different deposition durations. The experimental results showed that the thickness of the hybrid films varies from 373 to 540 nm with the increase in deposition time of the organic layer. Hybrid films showed improved surface morphology as compared to ZnSe film, confirmed by FESEM analysis.The energy-dispersive X-ray showed that the elemental compositions of the deposited hybrid films are of stochiometric ratio, while X-ray diffraction analysisof these films revealedenhanced crystallinity of the films compared toZnSefilm. Differential scanning calorimetry and thermogravimetric analysis specify that hybrid films are thermally more stable (up to 396 C) compared to ZnSe film (351C), probably due to higher crosslinking in the PP organic layer. To comprehend the chemical structure and optical characteristics of the hybrid films, FTIR and UV-visible spectroscopic investigations were done, respectively. The changes of chemical structure of the ZnSe/PPOMA hybrid thin films confirmed the polymerization process. The band gap (Eg) value of ZnSe film is found to be 2.54 eV,which is observed to increaseup to 2.88 eV with the increase of thickness of the PPOMA layer. Other optical parameters such as transmittance, absorption,extinction coefficients, refractive index, optical conductivity, Urbach energy and skin depth etc.are also studied to understand the properties of hybrid film. These results highlight the potential of these hybrid thin films for a wide range of applications, particularly insensing and optical devices.