Amorphous zinc-tin oxide thin films fabricated by pulsed laser deposition at room temperature
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Amorphous zinc-tin oxide thin films fabricated by pulsed laser deposition at room temperature P. Schlupp, H. von Wenckstern and M. Grundmann Universität Leipzig, Fakultät für Physik und Geowissenschaften, Institut für Experimentelle Physik II, Linnéstrasse 5, 04103 Leipzig, Germany ABSTRACT For a cost-efficient fabrication of homogeneous oxide thin films the usage of amorphous materials is favorable. They can be deposited at room temperature (RT) and represent an interesting alternative to amorphous silicon in electronics. Zinc-tin oxide is a promising n-type channel material for thin film transistors and consists of abundant elements, only, in contrast to the well-explored indium gallium zinc oxide. Here, the electrical and optical properties of room temperature deposited ZTO thin films are discussed. These films were fabricated via pulsed-laser deposition on glass substrates by ablating a ceramic target composed of ZnO and SnO2 in a 1:2 ratio. The resistivity has been controlled over seven orders of magnitude via the oxygen growth pressure. Further, the optical transmittance tends to be higher for higher oxygen growth pressures.
Fig. 1: XRD pattern of an amorphous ZTO thin film. The inset shows a SEM image of a ZTO thin film grown at pO2 = 10 Pa.
INTRODUCTION Amorphous semiconducting oxides are promising candidates for functional and costefficient thin films. Room temperature fabrication is additionally compatible with plastic
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substrates and makes flexible device applications feasible. Zinc-tin oxide (ZTO) is a promising amorphous n-type channel material1,2,3. Here, we present electrical and optical properties of ZTO thin films deposited by pulsed-laser deposition (PLD) at room temperature. Hall-effect measurements carried out with the van-der-Pauw method and transmittance measurements in the visible and UV spectral range were performed. EXPERIMENT Amorphous ZTO thin films were fabricated in three different growth chambers of different geometry by PLD. For target ablation we used a KrF excimer laser (O=248 nm). The ceramic targets consist of 66.7 at.% SnO2 and 33.3 at.% ZnO. The oxygen partial pressure during the deposition was varied from 0.03 Pa to 10 Pa. All thin films deposited on glass substrates (Corning 1737, 10×10 mm2) have a thickness between 500 nm and 1 Pm. For the electrical characterization Hall-effect measurements were performed using a home-built set up, which is described in Ref. 4. As ohmic contacts gold layers were sputtered onto the corners of the thin films. For X-ray diffraction (XRD) measurements a Philips X'pert with a Bragg-Brentano goniometer and Cu Kα radiation was used. Transmission measurements were performed using a Perkin Ellmer Lambda 40 UV/VIS spectrometer operating from 190 nm to 1100 nm with a step width of 0.1 nm and a measurement rate
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