High field-effect mobility zinc oxide thin film transistors produced at room temperature E. Fortunato * , A. Pimentel, L. Pereira, A. Gonc ßalves, G. Lavareda, H.  Aguas, I. Ferreira, C.N. Carvalho, R. Martins Department of Materials Science/CENIMAT, Faculty of Sciences and Technology, New University of Lisbon and CEMOP-UNINOVA, Campus da Caparica, 2829-516 Caparica, Portugal Abstract In this paper we present the first results of thin film transistors produced completely at room temperature using ZnO as the active channel and silicon oxynitride as the gate dielectric. The ZnO-based thin film transistors (ZnO-TFT) present an average optical transmission (including the glass substrate) of 84% in the visible part of the spectrum. The ZnO-TFT operates in the enhancement mode with a threshold voltage of 1.8 V. A field effect mobility of 70 cm 2 /V s, a gate voltage swing of 0.68 V/decade and an on-off ratio of 5 · 10 5 were obtained. The combination of transparency, high field-effect mobility and room temperature processing makes the ZnO-TFT very promising for the next generation of invisible and flexible electronics. Ó 2004 Elsevier B.V. All rights reserved. PACS: 85.30.T; 73.61.G; 78.66.H; 72.80.Ey; 68.55 1. Introduction Transparent electronics are nowadays an emerging technology for the next generation of optoelectronic devices [1]. The fundamental device that enables the realization of transparent circuits is a transparent transistor. The only possibility to perform transparent transistors is by using oxide semiconductors. Oxide semiconductors are very interesting materials because they combine simultaneously high/low conductivity with high visual transparency and have been widely used in a variety of applications (e.g. antistatic coat- ings, touch display panels, solar cells, flat panel displays, heaters, defrosters, optical coatings, among others) for more than a half-century. Transparent oxide semiconductor-based transistors have recently been proposed [2–5], using as active channel intrinsic zinc oxide (ZnO). These transistors present an on-to-off ratio of about 10 6 and relative low channel mobilities between 1 and 3 cm 2 /V s. The main advantage of using ZnO deals with the fact that it is possible to growth at/ near room temperature high quality polycrystalline zinc oxide, which is a particular advantage for electronic drivers, where the response speed is of major impor- tance. Besides that, since ZnO is a wide band gap material (3.2 eV), it is transparent in the visible region of the spectra and therefore, also less light sensitive. Besides these works Nomura et al. [6] also recently proposed a transparent transistor using as active channel a single crystal of InGaO 3 (ZnO) 5 . The most impressive aspect of this transistor is the high channel mobility of 80 cm 2 /V s, mainly due to the absence of structural defects and to a low carrier concentration. In this work we report the first results concerning the fabrication and characterization of a high field-effect mobility ZnO-thin film transistor (ZnO-TFT) deposited at room temperature by rf magnetron sputtering where the gate dielectric is based on silicon oxynitride and the drain and source are based on highly conductive gal- lium doped zinc oxide (GZO). Moreover, the process- ing technology used to fabricate this device is relatively simple and it is compatible with inexpensive plastic/ flexible substrate technology. * Corresponding author. Tel.: +351-21 294 8562; fax: +351-21 294 8558. E-mail address: elvira.fortunato@fct.unl.pt (E. Fortunato). 0022-3093/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2004.03.096 Journal of Non-Crystalline Solids 338–340 (2004) 806–809 www.elsevier.com/locate/jnoncrysol