Formation of ITO Nanowires Using Conventional Magnetron Sputtering

Abstract

ITO nanowires could be grown in oxygen-free Ar sputtering gas directly after the formation of ITO films with thicknesses of 10-50 nm using conventional magnetron sputtering. Growth of nanorods occurred at substrate temperatures of about 100 • C and higher, whereas nanowires with lengths of 1-10 μm and diameters of roughly 20-200 nm were formed at about 175 • C and above. The diameter, length and density of the nanowires could be controlled by varying the sputtering time, substrate temperature, and SnO 2 content in the ITO sputtering target. © The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. [DOI: 10.1149/2.0131407ssl] All rights reserved.Manuscript submitted April 8, 2014; revised manuscript received May 16, 2014. Published May 24, 2014 Nanowires (NWs) composed of metal oxides such as indium tin oxide (ITO) and ZnO have attracted significant attention for use in electrodes in electronic devices such as organic solar cells, light-emitting devices and various sensors.1 ITO NWs have been synthesized using vapor transport and thermal evaporation methods.1-3 However, from the viewpoint of low-cost production and ease of manufacture, it is desirable that such NWs be grown using magnetron sputtering, because this method is widely used to form ITO films for transparent electrodes in optoelectronic devices. ITO NWs have been produced using thermal evaporation at temperatures 2 that are higher than the maximum allowable temperature (ca. 300• C) in organic electronic device manufacturing processes. There have also been reports of ITO NW formation by a vapor-liquid-solid (VLS) mechanism using gold catalyst particles as seeds. 1In the present study, it was found that ITO NWs could be formed using conventional magnetron sputtering at low temperatures (ca. 175• C), without the need for metal catalyst nanoparticles. The technique involves NW growth directly after deposition of an ITO film on a substrate. This is beneficial because it allows ITO NWs to be formed on a range of different substrates.A conventional planar magnetron sputtering system (USP-66F, Universal Systems Co.), employing DC and RF (13.56 MHz) power was used in the present study. The sputtering targets with diameters of 4 inches were made from a mixture of In 2 O 3 and SnO 2 . The substrates used were 0.7-mm-thick Corning Eagle XG glass with dimensions of 100 × 100 mm. The common sputtering conditions applied in this paper were a DC power of 300 W and a sputtering gas pressure of 0.666 Pa. The sputtering gas was introduced into the chamber under a vacuum of 5 × 10 −5 Pa or less. The influence of additional sputtering conditions on the growth of ITO NWs was next investigated. The surface morphology was observed using field-emission scanning electron microscopy (FE-SEM; SU8020, Hitachi High-Technologies Co.)Influ...

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“…The first one requires relatively high growth temperatures, normally ranged between 700–1000 °C. The second one needs relatively low growth temperatures: from 250 to 600 °C [ 44 , 45 , 46 ]. Within the frame of the self—catalytic mechanism, the binary phase diagram of the In–Sn system [ 4 , 47 ] presents a eutectic point located near 125 °C.…”

Gas-sensing properties of ITO materials with different morphologies prepared by sputtering

“…Many methods have been tried to obtain ITO nanostructures, such as sputtering, thermal evaporation, and electron beam evaporation [14][15][16]. Among all of these methods, magnetron sputtering is the best choice, because of the faster deposition rate, better film quality, and the more stable repeatability [17,18].…”

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“…Furthermore, it is inferred that the conductivity of this film is a crystal defect derived from the film structure itself. In 1968, Philip found that the doping of Sn ions in the indium oxide film enhanced the conductivity of the overall film, and then produced In 2 O 3 :Sn film [ 7 ], now widely consolidated in indium tin oxide [ 8 , 9 , 10 ] applications.…”