Synthesis of Transparent Semiconducting Metal-oxides via Polymeric Precursor Route for Application in Thin-film Field-Ef
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Synthesis of Transparent Semiconducting Metal-oxides via Polymeric Precursor Route for Application in Thin-film Field-Effect Transistors Cleber A. Amorim1, Giovani Gozzi1, Dante L. Chinaglia1, Francisco José dos Santos1 and Lucas Fugikawa Santos1,2 1
Departamento de Física, Univ Estadual Paulista - UNESP, Av. 24A, 1515, CEP: 13500970,Rio Claro, SP, Brazil. 2 Departamento de Física, Univ Estadual Paulista - UNESP, R. Cristovao Colombo 2265, CEP 15054-000, São José do Rio Preto, SP, Brazil. ABSTRACT Solution-processed zinc oxide (ZnO) thin-film transistors (TFTs) obtained via hydrolysis/pyrolysis of an organic precursor present an excellent technique to obtain high performance electronic devices with low manufacturing cost. In the current work, we propose the use of an alternative deposition method, based on a polymeric precursor route (known as Pechini), to obtain solution-processed ZnO compact films as the active layer of TFTs. The elimination of the organic phase and the formation of inorganic thin-films was carried out by thermal treatment at different temperatures (ranging from 200oC to 500oC) and at different times (from 5 min to 2 hours), being monitored by UV-vis and infrared (IR) optical absorption spectroscopy. It was observed that, for temperatures above 400oC and treatment times superior to 30 min, the organic phase was completely eliminated, remaining only the inorganic (metal oxide) phase. The optical bandgap of the resulting ZnO films, determined from UV-vis absorption, is about 3.4 eV. The electrical characteristics (output and transfer curves) of the obtained devices demonstrate the feasibility of Pecchini method to build solution-processed metal oxide TFTs. The results for the electrical mobility of the majority charge-carriers (electrons) and for the threshold voltage were 0.39 cm2.V-1.s-1 and 0.45 V, respectively. INTRODUCTION Transparent semiconducting metal-oxides like zinc oxide (ZnO) and other tertiary and quarternary compounds have been widely used as active layer of thin-film transistors (TFTs) envisaging applications in large-area active matrix displays (AMDs) or totally transparent circuitry due to their considerably high charge-carrier mobility, optical transparency and stability [1]. Latest advances on this technology permitted the achievement of charge carrier mobilities considerably higher (up to 100 cm2V-1.s-1) than the mobility of amorphous Si (ca. 1 cm2V-1.s-1), which is the most currently used active material in AMDs. Higher mobilities make possible the fabrication of larger displays, with higher resolution and higher scanning frequencies, which are crucial for an increasingly more demanding market. Moreover, the use of transparent metal oxides as electrodes, active and dielectric materials of TFTs allows the production of totally transparent devices and displays, which has a striking appeal for innovative applications. Recently, TFTs comprising solution-processed metal oxides obtained via hydrolysis/pyrolysis of an organic precursor [2-9] have achieved electrical performance which
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