Process Characterization of Ultra-fine Tin Oxide Fibers Synthesis
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0951-E09-17
Process Characterization of Ultra-Fine Tin Oxide Fibers Synthesis Yu Wang1,2, Idalia Ramos2, and Jorge J. Santiago-Avilés1 1 Department of Electrical & Systems Engineering, University of Pennsylvania, 200 South 33rd Street, Philadelphia, PA, 19104 2 Department of Physics & Electronics, University of Puerto Rico, Humacao, 00791, Puerto Rico ABSTRACT Tin oxide (SnO2) with rutile structure is a wide-band gap semiconductor that has been used extensively in sensors and optoelectronic devices. A fibrous shape is especially favorable for the sensor applications. Micro-/nano- SnO2 fibers were synthesized from a precursor solution of dimethyldineodecanoate tin (C22H44O4Sn), poly (ethylene oxide) (PEO) and chloroform (CHCl3) using electrospinning and metallorganics decomposition techniques. Fourier-transform infrared spectroscopy, thermogravimetric and differential thermal analysis, and x-ray diffraction were used to reveal a series of physical and chemical changes from the starting chemicals to the final product of ultra-fine SnO2 fibers: the solvent CHCl3 evaporates during the electrospinning; the organic groups in PEO and C22H44O4Sn decompose with Sn-C bond in C22H44O4Sn replaced by that of Sn-O between 220 and 300°C, and the atomic arrangement transforms into the incipient structure between 300 and 380°C; the incipient rutile lattice develops into a relatively complete degree after sintering at higher temperatures up to 600°C. INTRODUCTION Semiconducting tin oxide (SnO2), with a rutile structure and a wide band gap (Eg=3.6eV), is chemically inert, mechanically hard and thermally heat-resistant and has a wide variety of existing and potential applications in sensors and optoelectronics such as solar cells, displays and electrochromic devices [1-3]. While the optoelectronics applications of the oxide are mostly due to its wide band gap that makes it transparent up to ultra violet light, its sensors applications are derived from its conductivity modulation of by species chemisorbed on its surface and their interaction with oxygen vacancies in its lattice. Although the two kinds of applications require SnO2 with different nature and levels of crystal defects such as dopants and oxygen vacancies, both have taken the advantage of the thin-film shape, and therefore, SnO2 thin films have been synthesized by various methods, such as evaporation [4], sputtering [5], spray pyrolysis [6], chemical vapour deposition [7] and sol-gel process [8, 9], and their synthetic processes have been characterized and correlated to their final stoichiometry, phase constituents and crystal defects. The preference for thin films in sensor applications is due to its higher surface-tovolume ratio than that of the bulk shape, and its restriction to the grain growth. The ratio is even higher for a fibrous shape. Unfortunately, SnO2 fibers has been synthesized by only a limited number of ways, such as laser ablation [10], thermal decomposition [11], oxidizing electrodeposition of template [12], and electrospinning [13]. Of these methods, elec
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