Structural and electrical properties of single Ga/ZnO nanofibers synthesized by electrospinning
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ilippe Sonntag Hutchinson S.A, Research Center, Rue Gustave Noury - BP31, F-45120 Chalette-sur-Loing, France
Philippe Ricoux TOTAL S.A/DG, Tour Coupole, 29F40, 92078 Paris La Defense Cedex, France
Gideon S. Gradera) Department of Chemical Engineering, Technion—Israel Institute of Technology, Haifa 32000, Israel (Received 23 January 2012; accepted 28 March 2012)
Nanofibers (NFs) of Ga-doped ZnO (GZO) were prepared by electrospinning of polymer–salts solution. Sintering profiles reported in the literature led to loss of the fibrous structure. Hence, the morphology, thermal stability, and phase composition of green and sintered fibers were investigated as function of sintering conditions to elucidate this degradation process. Optimal results were obtained at 400 °C for 30 min. This low temperature sintering of GZO fibers has not been previously reported. The fibers were porous with a significant surface area, making it possible to test their sensitivity to environmental changes. In particular, the response of the GZO NFs to changes in humidity was demonstrated for the first time. The electrical and sensing properties of single NFs prepared at these conditions were studied using a field-effect transistor mode.
I. INTRODUCTION
Transparent conductive oxides (TCOs) based on doped zinc oxide have been used in many applications including optoelectronic devices, photovoltaic (PV) cells, and sensors.1–6 The low cost of zinc, as compared to indium [in indium tin oxide (ITO) films], and the increasing area of PV systems has been driving the increased demand for lower cost TCO films. In addition to the twodimensional films, one-dimensional nanostructures, such as ZnO nanofibers (NFs), offer the advantage of a large surface-to-volume ratio as well as a conducting pathway along the fiber length. For sensor applications, a porous fiber structure would be optimal since the surface to volume ratio in such a fiber would increase, leading to increased potential sensitivity. Yet for ZnO fibers, the optimal way to form porous NFs has not been reported. Different methods have been developed for the NFs fabrication,7–13 including the laser ablation metal catalytic vapor–liquid–solid method,7–9 the oxide-assisted catalystfree method,10–12 and solution techniques.14 Nevertheless, the electrospinning technique, invented originally in 1934,15 offers several advantages, including relative low cost and simplicity.16,17 NFs of many materials, including organic, ceramic, and metallic nature [e.g., Polyvinyl Alcohol (PVA), a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.118 1672
J. Mater. Res., Vol. 27, No. 13, Jul 14, 2012
http://journals.cambridge.org
Downloaded: 13 Mar 2015
Polyethylene Glycol, Polylactic acid, TiO2, carbon–silver composite, and more], have been prepared by this technique. These NFs can be found in many applications such as membranes, catalysts, electronic devices.18–24 Ceramic and polymeric sensors can be found in varied applications. Ceramics have the advantage of long-term stability
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