Characterization of Zinc Oxide Thin Films Deposited by rf Magnetron Sputtering on Mylar Substrates
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Characterization of Zinc Oxide Thin Films Deposited by rf Magnetron Sputtering on Mylar Substrates Elvira Fortunato1, Patrícia Nunes1, António Marques1, Daniel Costa1, Hugo Águas1, Isabel Ferreira1, Maria E. V. Costa2 and Rodrigo Martins1 1 Department of Materials Science/CENIMAT, Faculty of Sciences and Technology, New University of Lisbon and CEMOP-UNINOVA, 2825-114 Caparica, Portugal 2 Department of Ceramics and Glass Engineering/UIMC, University of Aveiro, 3810-193 Aveiro Portugal ABSTRACT Aluminium doped zinc oxide thin films (ZnO:Al) have been deposited on polyester (Mylar type D, 100 µm thickness) substrates at room temperature by r.f. magnetron sputtering. The structural, morphological, optical and electrical properties of the deposited films have been studied. The samples are polycrystalline with a hexagonal wurtzite structure and a strong crystallographic c-axis orientation (002) perpendicular to the substrate surface. The ZnO:Al thin films with 85% transmittance in the visible and infra-red region and a resistivity as low as 3.6×10-2 Ωcm have been obtained, as deposited. The obtained results are comparable to those ones obtained on glass substrates, opening a new field of low cost, light weight, small volume, flexible and unbreakable large area optoelectronic devices. INTRODUCTION ZnO:Al have been extensively studied in recent years, because of their material low cost, relatively low deposition temperature, non-toxicity and stability in hydrogen plasma, compared with indium tin oxide (ITO) and tin oxide (SnO2). Nowadays there is a great interest in replacing glass substrates with polymer substrates, particularly in flat panel display and touch screens technologies, where low volume, lightweight, and robustness are important. Besides that the added flexibility of polymer substrates opens new field applications that utilize curved surfaces, like for example amorphous silicon large area flexible position sensors [1]. Due to these new demands some authors start preparing ZnO:Al films deposited on organic substrates like polyisocyanate [2, 3]. Recently we presented the first results on ZnO:Al thin films deposited on Mylar substrates [4]. In this paper we give a more detailed description on the preparation as well as on the characterization of the obtained films. EXPERIMENTAL DETAILS The substrates used in this work are polyester (Mylar type D) foils from Dupont with a standard thickness of 100 µm. The main reason for chosing such polymer, deals with the fact that, the optical properties (refractive index of 1.65 and a transmittance of 90% in the wavelength range from 0.4 to 2.4 µm) are very similar to that of glass substrates. Before depositing the ZnO thin films, the substrates were ultrasonically cleaned in a detergent bath, followed by isopropyl alcohol and dried in nitrogen. The substrates (10 cm × 10 cm) were placed inside the chamber and then evacuated until a base pressure of 7×10-7 mbar. The ZnO:Al thin F3.21.1
films were produced by r.f. magnetron sputtering from a commercially available sintered ce
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