Effect of Annealing on the Development of Fully Transparent Ternary V-O-Na-Si Mixed Metal Oxide Thin Films from Polymer-Assisted Dip-Coated V₂O₅

Abstract

Both transparent oxides and transparent conductive oxides are of particular research interest for future applications in flexible, optically transparent thin film transistors and luminescent devices. We report the formation of a transparent oxide material based on the interdiffusion of Na-O and Si-O species with dip-coated V 2 O 5 thin films on a borosilicate glass substrate. The deposition process used a facile solution processed dip-coating technique in the high-rate draining regime. Liquid precursors of vanadium alkoxide and alkoxide-polyethylene glycol mixtures were used for thin film deposition. We examine the effect of annealing condition on the phase conversion process, morphology and optical transmittance due to the conversion of the V 2 O 5 films to completely transparent ternary mixed metal oxide thin films. The work also examines the role of polymer-assisted deposition on the development of the V-O-Na-Si transparent thin films during different annealing conditions. Polymer-assisted V 2 O 5 thin films on glass are shown to convert to optically clear thin films during annealing, with a transparency >95% across the visible spectrum, and a blue-shift of the absorption edge to maintain >90% transparency at 380 nm. Thin film transistors are the fundamental building blocks for stateof-the-art microelectronics 1 and metal oxide materials are critical for channel materials and transparent contacts in many of the devices. Transparent conductive oxides 2 (TCO) and transparent thin films (TTF) are widely used in optoelectronic applications as they offer transparency across a broadband frequency range, or indeed in specific spectral regions while maintaining some properties of a metallic conductor in addition to semiconducting behavior in many cases. 3These properties make them ideal for incorporation into devices such as thin film transistors (TFT), 1,4 photovoltaics 5 and electrochromic windows, 6-9 and optical coatings as pertinent examples. Lower-cost precursor routes that lead to TCOs are appealing, particularly for TFT and photovoltaic devices, since they are solution-processable, do not require the use of high-vacuum processing methods and in principal may allow coating of non-planar substrates. TFTs using oxide semiconductors have positive attributes such as high field effect mobility, wide band gaps, can be grown by many methods, and function in an amorphous state. The range of oxide compositions may widen with the use of liquid-based precursors for solution-processed deposition of the coatings. 10Transition metal oxides have a controllable electrical conductivity, from almost insulating to degenerately semiconducting, 11 with previous work demonstrating that conductivity alterations are possible through additive selection.12 Transition metal oxides are also an area of interest owing to the wide variety of possible elemental compositions and the large range of crystal structures possible, highlighting their potential use in many fields with particular emphasis on emerging transparent electronics. Many new...

A Rare Example of Four-Coordinate Nonoxido Vanadium(IV) Alkoxide in the Solid State: Structure, Spectroscopy, and Magnetization Dynamics

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