Mechanical Properties of Indium Tin Oxide on Polyethylene Napthalate Substrate
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Mechanical Properties of Indium Tin Oxide on Polyethylene Napthalate Substrate S. Bhagat1,2, Y. Zoo1,2, H. Han1,2, J. Lewis3, S. Grego3, K. Lee4, S. Iyer4, and T. L. Alford1,2 1 School of Materials, Arizona State University, Tempe, AZ, 85287, USA 2 Flexible Display Center at Arizona State University, Tempe, AZ, 85284, USA 3 RTI International Inc., Research Triangle Park, NC, 27709, USA 4 Electrical and Computers Engineering, North Carolina A&T State University, Greensboro, NC, 27411, USA ABSTRACT This work investigates the mechanical properties of indium tin oxide deposited on polyethylene napthalate substrates by rf sputtering method as a function of deposition conditions, including rf power, substrate temperature, and substrate treatment. X-ray diffraction analysis, Rutherford backscattering spectrometry and mechanical bending analysis are used for characterization of samples. The best mechanical performance represented by bending of the film stack is obtained from high substrate temperature and low rf power. Plasma treatment gases also influence mechanical properties, with mixture of nitrogen and hydrogen gases producing the best results. This work provides an initial understanding of the impact of sputter process conditions on filmÃs mechanical performance.
INTRODUCTION Continued demand and development has paved the way for extensive research in the field of flexible displays electronics and transparent electrodes [1-3]. Polymeric substrates enjoy the benefit of being lightweight, mechanically robust, and transparent. Polyethylene napthalate (PEN) is one of the prominent polymeric substrate. It has better dimensional stability and thermal properties than the commonly used polyethylene terapthalate [4]. The most commonly used transparent electrode material in displays is indium tin oxide (ITO); it is also used as the anode in organic light emitting diodes. However, ITO interconnects fail under lower mechanical strain than the other device layers [5-6]. There is limited knowledge about the correlation of growth conditions their impact on the mechanical robustness of ITO. The goal of the present study is to elucidate the correlation between growth conditions and mechanical bending. In this work, we have systematically investigated the effect of deposition rf power, substrate temperature, and plasma gases on the mechanical properties of ITO films deposited on PEN by rf sputtering.
EXPERIMENTAL DETAILS To study the effect of plasma gases on the mechanical performance, represented by mechanical bending of ITO on PEN substrates, the substrates were plasma treated for 2 minutes under 10W rf diode plasma at 40mTorr using either Ar, N2/H2 (90%/10%), or O2 gases, prior to deposition inside the sputter chamber. After plasma treatment, ITO films were deposited on PEN
substrates using rf sputtering using a 7.62 cm sintered In2O3 powder sputtering target containing 10% SnO2 by weight. The distance of substrate and target was kept constant at 6 cm for all the samples. The base pressure of the chamber was approx
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