Highly Conductive In4Sn3O12 Films Prepared by Pulsed Laser Deposition
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1102-LL01-10
Highly conductive In4Sn3O12 films prepared by pulsed laser deposition David H O'Neil1, Vladimir Kuznetsov1, Robert Jacobs2, Martin O Jones1, and Peter P Edwards1 1 Inorganic Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3RQ, United Kingdom 2 Surface Analysis Facility, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom ABSTRACT Highly conductive (> 103 Ω-1cm-1) and transparent (~ 90%) In4Sn3O12 films have been deposited using pulsed laser deposition (PLD) on glass substrates held at a temperature of 500ºC under varying pressures of oxygen (2.5 mTorr ≤ PO2 ≤ 15 mTorr). The crystallinity and the roughness of the films were found to increase with the pressure of oxygen used during deposition. Electron concentrations of the order of 5x1020 cm-3 and mobilities as high as 30 cm2V-1s-1 were derived from the measurement of Hall coefficients. Both the electronic transport and optical properties of the films were found to be strongly sensitive to the pressure of oxygen used during deposition. INTRODUCTION The n-doped post transition metal oxides of indium, tin and zinc offer the rare combination of high electrical conductivity, high infrared reflectivity and optical transparency at visible wavelengths and have become known as transparent conducting oxides (TCOs). The conductivity of commercially available tin-doped indium oxide (ITO), approximately 104 Ω-1cm-1, is comparable to that of some metals. The electron concentration in such a material is of the order of 1021 cm-3 and yet the material still exhibits optical transparency.[1] It is this rare combination of near metallic conductivity and substantial optical transparency that has lead to the widespread exploitation of transparent conductors and in particular ITO as transparent thin film electrodes in flat panel displays and photovoltaic devices. With increased technological demand and the escalating cost of indium resources, the development and optimization of new materials for transparent electrode applications represents one of the major challenges for both liquid crystal display and photovoltaic industries. As yet, there is no suitable candidate that displays the correct portfolio of properties to replace costly ITO. However, several In2O3-based multi-component oxides are emerging with properties potentially suitable for specialized applications.[2] In4Sn3O12, the ternary oxide formed within the In2O3-SnO2 system [3] is perhaps the one of the most attractive alternatives to ITO because of its reduced indium content and consequent lower cost. As a ceramic, the material In4Sn3O12 exhibits a conductivity of approximately 120 Ω-1cm-1, one order of magnitude less than that of ceramic ITO.[4] However, there are reports that as thin film In4Sn3O12 may display conductivities and transparencies comparable to ITO.[5,6,7] Highly conductive and transparent In4Sn3O12 films have been prepared by Minami et al. by DC magnetron sputtering using In2O3-SnO2 targets with a Sn content between 45 – 55%.[7]
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