Halide doping effects on transparent conducting oxides formed by aerosol assisted chemical vapour deposition

Nuruzzaman Noor,Ivan P Parkin

doi:10.1016/j.tsf.2012.10.110

Abstract

We report on the effect of halide doping on the Aerosol-assisted Chemical Vapour Deposition of tin oxide. Specifically, the importance of precursor interactions is highlighted. A halide exchange reaction involving part substitution of the tin precursor is believed to occur in the solvent; the complex acting as a marker for improved films with improved transparent-conducting properties. Precursor mixtures of butyltin trichloride and potassium halide (X=F, Cl, Br, I) in propan-2-ol were deposited at a substrate temperature of 450°C using air carrier gas. Hall Effect results indicate that fluorine gave the best performing n-type transparent conducting thin films that exhibited high optical transparency (>80% at 550nm) and resistivity values of 4.9×10−4Ω.cm, with charge carrier density and carrier mobility values of 8.85×1020cm−3 and 15cm3/V.s respectively. Such parameters yield high figures of merit.

Highlights

Transparent conducting oxides (TCOs) are a class of multifunctional material which demonstrate both electrical conductivity and optical transparency over visible light wavelengths
The high performance properties are due to the ability to dope the SnO2 framework, enhancing the intrinsic n-type semiconducting properties by an order of magnitude or more [1]
The best SnO2 dopant to date has been fluorine (FTO). It introduces an extra charge carrier into the system per dopant ion; its effectiveness attributed to the ease with which it substitutes for oxygen within the SnO2 framework

Summary

Introduction

Transparent conducting oxides (TCOs) are a class of multifunctional material which demonstrate both electrical conductivity and optical transparency over visible light wavelengths. This is made possible due to their intrinsic semiconducting nature and wide bandgap (>3.2 eV) respectively [1,2]. The high performance properties are due to the ability to dope the SnO2 framework, enhancing the intrinsic n-type semiconducting properties by an order of magnitude or more [1]. The best SnO2 dopant to date has been fluorine (FTO). It introduces an extra charge carrier into the system per dopant ion; its effectiveness attributed to the ease with which it substitutes for oxygen within the SnO2 framework. Since the integrity of the bandgap is largely preserved, optical transparency properties are maintained which allows the concurrence of two normally conflicting physical phenomena

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Conclusion