International Journal of Innovative Research in Science, Engineering and Technology
MenuISSN ONLINE(2319-8753)PRINT(2347-6710)
ISSN ONLINE(2319-8753)PRINT(2347-6710)
S.Hemalatha 1, J.Tamil Illakkiya 1, Rachel Oommen 2
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Ternary ZnIn2S4 (ZIS) films were deposited on a glass substrate using Spray pyrolysis method. The properties of as-deposited ZnIn2S4 film and annealed films were characterized using the XRD, UV-Vis-NIR spectroscopy and Raman spectrum, FESEM, EDAX and Photoluminance. The XRD result shows the hexagonal structure. Optical study shows the maximum transparency of nearly 88% for 550°C annealed film (ZIS-T5).Absorption edge for as-deposited (ZIS) , annealed films (ZIS-T1 -350°C, ZIS-T2 - 450°C and ZIS-T3 - 550°C) values found to be 536 nm and 525 nm, 498nm and 441nm.Band gap(Eg) values of the as-deposited, annealed film (350°C, 450°C, 550°C) values were estimated at 2.79 eV,2.89 eV, 2.94 eV and 3.3eV respectively. Morphology of as-deposited ZnIn2S4 film shows the rulles dollops rather than a microsphere, EDAX spectrum showed the Composition of the film closed to the stoichiometric compound. From the Pl spectrum strong emission band at ∼470 nm was observed for as-deposited (ZIS) and annealed films (ZIS-T1, ZIS-T2).
Keywords |
| Text detection, ZnIn2S4, annealing effect, nebulized spray pyrolysis. |
INTRODUCTION |
| Image AIIB2 IIIC4 VI ternary semiconducting materials are widely studied because of their excellent potential applications such as electro-optic, optoelectronic, and nonlinear optical devices. Most of these compounds have defect chalcopyrite space group (S24) or defect stannite space group (D112d) structure [1]. ZnIn2S4 (ZIS) compound comes from the thiospinel family (MIn2S4, M=Cd, Fe, Ni, Mn) [2].The ZnIn2S4 (ZIS) material properties similar to CdS properties, it is n-type semiconductor material [3]. ZnIn2S4 is found as a strong candidate photovoltaic material for a novel type of thinfilm solar cell fabricated by sputtering process [4]. In particular, in the layered structure of ZnIn2S4 two kinds of intrinsic defects appear relevant: (i) random stacking faults in the layer structure; (ii) Zn ions in the In sub lattice, In ions in the Zn sub lattice and vacant sites in both Zn and In sub lattices. These defects characterize the electronic properties of the material because they give rise to charged centres acting as donors or acceptors [5]. ZnIn2S4 have different polymorphs and used for many applications, hexagonal ZnIn2S4 exhibit the photoluminescence and photoconductivity, cubic ZnIn2S4 exhibit thermoelectricity [6]. The ZnIn2S4 (ZIS)thin film prepared by various methods such as Successive ionic layer adsorption and reaction (SILAR) [7], solvothermal method [8,9], facile solvothermal method[10], hydrothermal method [11-13] electro deposition [14], microwave-assisted synthesis equipment[15], CBD method[16], thermal sulfidation of the oxidation precursor[17], spin coating method [18], magnetron sputtering [19], MOCVD [20], spray pyrolysis [21,22], Atomic layer deposition [23,24]. ZnIn2S4 thin film have different morphologies such as nanoribbons and nano wires [25], microspheres [26].Compared to other methods spray pyrolysis is basically a chemical process that involves spraying aqueous solution onto a substrate held at high temperature. In the present work, ZnIn2S4 (ZIS) thin films are prepared by the novel technique in a liquid phase (Nebulized Spray pyrolysis) and Characterized for structural, optical and Photoluminance properties. Post deposition heat treatment was carried out to see the effect of annealing temperature on its properties. |
| ZnCl2, SC (NH2)2 obtained in Merck, Indium Chloride (InCl3) (Himedia), used as a precursor. Molar solution of the precursors are prepared by dissolving appropriate amount of materials in deionized water .Chemically cleaned 2.5 cm X 2.5 cm glass slides are used as deposit substrate. A simple glass nozzle was fabricated to give a fine and very small droplets of precursor solution which is driven by cool air from the compressor. The pressure of the carrier gas (air) was kept constant at 1 bar. The Sprayed ZIS thin films were obtained from an aqueous solution containing Zinc chloride (0.3180 M), Indium chloride (1.4868 M) and thiourea (0.0682M) respectively. Equal volume of these three solutions mixed together 5 to 10 mins and then added 10 drops of ethanol to form smooth solutions. The substrates were mounted on an aluminium base attached to a heating hot plate. The substrate temperature maintained at 350°C. This substrate temperature was precisely maintained within ± 5°C of the desired value. The temperature was controlled by digital micro controller and the substrate temperature was measured by attaching a thermocouple near the substrate. Nozzle to substrate distance was kept constant at 50mm. Spraying was consummate using novel glass nebulizer. The possible chemical reaction that takes place on the heated glass substrate produces a well adherent uniform yellow ZnIn2S4 (ZIS) film. The as-deposited samples are annealed at various temperatures 350°C, 450°C, 550°C to study the influence of annealing and the samples labelled as ZIS, ZIS-T1, ZIS-T2 and ZIS-T3 for convenient depiction. |
| The X-ray diffraction (XRD) patterns, obtained on a XPERT-PRO analytical, X-ray diffractometer using Cu-Kα radiation (1.5406Å) at the applied current 30 mA and accelerating voltage 45 kV respectively. UV–Visible diffuse reflectance spectra were recorded on (UV–Vis-NIR) spectro- photometer (ModelJASCO-V-670). The information related to morphology and elemental composition of the samples are recorded by Field emission scanning electron microscopy (FESEM) attached to an energy dispersive X-ray spectroscopy (EDS) by OXFORD X-act tescan instrument. Raman spectra of the film were taken by HORIBA-LABRAM HR-800 equipment. Photoluminance of the film is characterized by Horiba JobinYvon Fluoromax-4 spectrofluorometer. |
EXPERIMENTAL RESULTS |
| (A) Structural Characterization |
| X-ray Diffraction studies |
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| XRD diffraction technique confirmed the ZnIn2S4 film crystallinity and phase composition of the material. The XRD patterns of the ZIS as-deposited and annealed films are shown in Fig1. Well defined diffraction peaks observed in the XRD pattern of ZnIn2S4 thin films (104), (111), (110) and (115) well indexed to be hexagonal phase of ZnIn2S4 thin films (JCPDS-65-2023).No peaks attribute to other phase are observed and indicate the formation of pure hexagonal ZnIn2S4. The peak intensities are not too high. As the annealing temperature increases to 350°C peak intensity increases, for (104) plane, then decrease at 450°C,then increases at 550°C at the same time additional (110) plane peak observed at 450°C and (115) plane peaks at550°C . When the annealing temperature increases to 550°C the yellow colour ZnIn2S4 film fully changed in to white colour [15].The grain size of the films calculated using Debye Scherrer formula , |
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| The emission spectrum was engaged to study the surface structure and excited states. Fig.9 shows the Photoluminescence spectra of ZnIn2S4 thin film as-deposited and annealed samples (ZIS, ZIS-T1, ZIS-T2 and ZIS-T3). For the as-deposited and annealed film (ZIS-T1, ZIS-T2) pl spectrum consists of five emission bands appeared at 452 nm, 484 nm, 493 nm, 537 nm and 570 nm respectively. The PL spectrum of as-deposited (ZIS) and annealed film (ZIST1, ZIS-T2) consists of strong emission band at ∼470 nm. The peak intensity was gradually decreases with increasing in the annealing temperature. Disappearance of the peak was observed for (ZIS-T3) spectrum annealed at 550°C. The emission peak intensity at 570 nm was blue shifted to 537 nm. |
CONCLUSION |
| ZIS as-deposited and annealed films deposited using nebulized spray pyrolysis method. The XRD shows all ZIS asdeposited and annealed film exhibited hexagonal phase. UV-Vis -NIR spectrum shows the maximum transparency of which is nearly 88% for annealed film (ZIS-T5).Absorption edge was found to be 536 nm and 525 nm, 498nm and 441nm for ZIS ,ZIS-T1, ZIS-T2 and ZIS-T3 films. Band gap (Eg) values for ZIS, ZIS-T1, ZIS-T2, ZIS-T3 thin films value estimated to be 2.79 eV, 2.89 eV, 2.94 eV and 3.3eV respectively. Using FESEM image shows the as-deposited ZIS (ZnIn2S4) film shows the rulles dollops. Composition of the film closed to the stoichiometric value. In PL studies strong emission peak was observed at ∼470 nm was observed for as-deposited (ZIS) and annealed films (ZIS-T1, ZIST2). |
References |
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