Effect of substrate temperature on the crystal growth orientation of SnO2:F thin films spray-deposited on glass substrates

doi:10.1016/j.jnoncrysol.2010.06.076

Journal of Non-Crystalline Solids

Volume 356, Issues 44–49, 1 October 2010, Pages 2557-2561

https://doi.org/10.1016/j.jnoncrysol.2010.06.076 Get rights and content

Abstract

Transparent conducting thin films of SnO2:F have been deposited onto preheated glass substrates by a spray pyrolysis technique using dihydrate stannous chloride (SnCl₂·2H₂O) and ammonium fluoride (NH₄F) as precursors, and mixture of water and ethanol as solvent. The preheated substrate temperature was changed from 250 °C to 600 °C. X-ray diffraction spectra show that the as-deposited films are polycrystalline SnO₂ with a tetragonal crystal structure. Surface morphology, optical properties (such as transmission, color), and conductivity were investigated using Super depth of three-dimensional field microscopy system, UV–VIS–NIR spectroscopy, Four-point probe. The obtained results revealed that the structures and properties of the films were greatly affected by substrate temperature. The lowest sheet resistance of 4.0 Ω was obtained with moderate optical transmission (up to 75% at 600 nm). The relationship between the crystal growth orientation and surface morphology, optical properties (such as transmission, color), and electrical properties, was discussed in detail in this article.

Introduction

The highly transparent and conductive thin films, owing to its high transmittance and conductivity, have been wide device applications [1]. Thin films of non-stiochiometric metal oxides like tin oxide; indium oxide; zinc oxide and their alloy when deposited under appropriate conditions and doped suitably impurities for well-suited applications are optically transparent as well as electrically conducting. SnO₂, has a tetragonal structure, similar to the rutile structure with the wide energy gap of Eg = 3.67 eV, and behaves as an n-type semi-conductor [2] have been widely used in different devices like solar cells as transparent and protective electrodes [3], flat panel collectors as spectral selective windows [4], sensors for detection of gases [5], [8], and photo-thermal converters, providing thermal insulation for houses [6].

Fluorine doped tin oxide (SnO₂:F) has been prepared by several methods: Magnetron sputtering [7], reactive evaporation [8], chemical vapor deposition [9] and spray pyrolysis [10]. These spray pyrolyses are well-suited for the preparation of doped tin oxide thin films because of its simple and inexpensive experimental arrangement, ease of adding various doping materials, reproducibility, high growth rate and mass production capability for uniform large area coatings [11].

The optical and structural properties of spray deposited SnO₂:F films have also been well studied, perhaps because of greater interest in this direction. As there is an increasing demand for these materials in the optoelectronic devices, there is a need to understand the transport properties of doped SnO₂ thin films. As far as devices are concerned, the highest reported photovoltaic conversion efficiency for spray deposited SnO₂ based Si solar cell is 12.3% [12]. In this paper, the effects of substrate temperature on the crystal growth orientation of SnO₂:F thin films are studied by X-ray diffraction in detail, and the changes of optical and electrical properties with growth orientation are also studied. The prime aim of this work is to produce highly conducting F doped tin oxide thin films from SnCl₂ precursor solution and to investigate their structural and electrical properties.

Section snippets

Experimental

Fluorine doped tin oxide (SnO₂:F) films were prepared using homemade spray pyrolysis experimental instruments in the open environment. The dihydrate stannous chloride (SnCl₂·2H₂O) was used as the source for tin. The fluorine doping was achieved using ammonium fluoride (NH₄F) [13]. Low-iron glasses (100 × 100 × 3.2 mm) were used as substrates. The substrates were cleaned using distilled water and ethanol. The substrate temperature was varied from 250 °C to 600 °C. Films of about 1 um thick were grown.

Results

We employed the X-ray diffraction technique to get a first impression of the main crystalline phases and the possible orientation of crystallites in the films prepared at different conditions. The X-ray diffraction spectra of SnO₂:F films prepared at 30 s spraying time and at 250, 300, 400, 500 and 550 °C substrate temperature on low-iron glasses are shown in Fig. 1. The plots in Fig. 1 give an obvious overview of the changes in relative peak intensities corresponding to the different crystal

Structure analysis

The structural characterization is very important in explaining the optical and electrical properties of SnO₂:F thin films. The crystal structure of the as-deposited SnO₂:F thin films were determined by X-ray diffraction technique. The XRD patterns obtained for the films grown on glass substrates at different substrate temperature were studied in the 2θ range of 10 to 70° and are depicted in Fig. 1. The matching of observed and standard d values confirms that the deposited films are of SnO₂

Conclusions

Spray pyrolysis is a cost effective method used in preparing highly conductive SnO₂:F films, having high transparency. Structural investigations using XRD reveal that the layer is composed of polycrystalline SnO₂ with a tetragonal crystal structure only. The lattice parameter values are not affected by the doping. The preferred orientation depended on substrate temperature, which is in (200) direction in the SnO₂:F deposited at the substrate temperature of > 300 °C. The lowest sheet resistance of

References (23)

Gregory J. Exarhos et al.
Zhou
Thin Solid Films
(2007)
K.L. Chopra et al.
Thin Solid Films
(1983)
G. Frank et al.
Sol. Energy Mater.
(1983)
M. Bender et al.
Thin Solid Films
(1998)
B. Thangaraju
Thin Solid Films
(2002)
A.V. Moholkar et al.
Mater. Lett.
(2007)
A. Smith et al.
Thin Solid Films
(1995)
G. Gordillo et al.
Thin Solid Films
(1994)
A.V. Moholkar et al.
Sol. Energy Mater. Sol. Cells
(2008)
A.L. Dewar et al.
J. Mater. Sci.
(1984)

Wang yude

Solid State Electron.

(2004)

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Effect of substrate temperature on the crystal growth orientation of SnO2:F thin films spray-deposited on glass substrates

Abstract

Introduction

Section snippets

Experimental

Results

Structure analysis

Conclusions

Thin Solid Films

Thin Solid Films

Sol. Energy Mater.

Thin Solid Films

Thin Solid Films

Mater. Lett.

Thin Solid Films

Thin Solid Films

Sol. Energy Mater. Sol. Cells

J. Mater. Sci.

Solid State Electron.

Effect of substrate temperature on the crystal growth orientation of SnO₂:F thin films spray-deposited on glass substrates