The effect of solvents and the thickness on structural, optical and electrical properties of ITO thin films prepared by a sol–gel spin-coating process

Mohsen Moradi-Haji Jafan,Mahboubeh Rabbani,Mohammad-Reza Zamani-Meymian,Rahmatollah Rahimi

doi:10.1007/s40097-014-0089-y

Mohsen Moradi-Haji Jafan, Mahboubeh Rabbani + Show 2 more

Open Access

https://doi.org/10.1007/s40097-014-0089-y

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Abstract

In this study, tin-doped indium oxide (ITO) thin films were produced by the sol–gel spin-coating technique with an inexpensive salt of indium (In(NO3)3·H2O) and SnCl4 as indium and tin precursors (the molar ratio of In:Sn was 9:1), respectively. Then the prepared thin films were annealed in the temperature of 550 °C under argon atmosphere (the pressure of 10 torr). Polyvinylalcohol (PVA) was used as stabilizers in the synthesis of ITO sol. The prepared ITO thin films were characterized by EDX, XRD, FT-IR, UV–Vis spectroscopy and SEM images. The XRD patterns of the thin films indicated the main peak of the (2 2 2) plane corresponded to indium oxide with high degree of crystallinity. The FT-IR spectroscopy confirmed that indium tin oxide has been prepared by appearance of a peak at 470 cm−1 that can be assigned to the vibrations of In–O bonds. The optical direct band gap of ITO thin films was calculated about 3.98–4.17 eV by optical transmittance measurements. The grain size of ITO nanoparticles was obtained at about 25–50 nm by SEM images. The electrical characterization was done by the four-point probe method to determine the sheet resistance and resistivity. The effects of coating number on ITO thin films properties were investigated. The low resistivity (sheet resistance of 2.5 kΩ/cm2) and highly transparent films were obtained that can be applied as covers on heater windows. Appearance of a peak at 470 cm−1 can be assigned to the vibrations of In–O bonds and are characteristic of cubic In2O3.

Highlights

Thin films of transparent semiconductor have attracted interest because of its good transparent and conductive properties for the potential applications in electronic fields such as heater windows, dye synthesized solar cells and transparent electrodes [1,2,3]
The morphologies of the Indium tin oxide (ITO) thin films were observed by scanning electron microscopy (SEM) images (Fig. 1)
We have reported a simple method for the preparation of SGS ITO thin films on a glass substrates at 550 °C by aqueous precursors

Summary

Introduction

Thin films of transparent semiconductor have attracted interest because of its good transparent and conductive properties for the potential applications in electronic fields such as heater windows, dye synthesized solar cells and transparent electrodes [1,2,3]. The sol–gel method has several advantages, including simplicity, low cost, controlled doping levels and feasible preparation of large area films [6]. This method, as a chemical route procedure can be combined with deposition techniques such as spin- and dip-coating for use in the preparation of thin films [20,21,22,23]. This method is a very easy and economical technique to get high-quality ITO thin films.

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