33 Mater. Res. Soc. Symp. Proc. Vol. 1371 © 2012 Materials Research Society DOI: 10.1557/opl.2012. VLS Synthesis and Characterization of SnO 2 Nanowires Dulce N. Castillo, Tomás D. Becerril, Enrique R. Andrés, Héctor J. Santiesteban and Godofredo G. Salgado. Posgrado en Dispositivos Semiconductores, Benemérita Universidad Autónoma de Puebla, Av. 14 Sur y San Claudio s/n, Ciudad Universitaria, C.P.72570, Puebla, Pue., México. ABSTRACT We have synthesized core-shell 1D nanostructures by the Vapor-Liquid-Solid (VLS) mechanism. Gold (Au) was used as a catalyst and tin oxide (SnO) powder as a precursor; the growth temperature was of 600 °C. These structures were characterized by XRD, SEM, TEM, EDS, and PL. The nanowires have an average diameter of 20 nm and their lengths are of tens of micrometers; the core is tin dioxide (SnO 2 ) with the tetragonal rutile structure and it has an average diameter of 12 nm; the shell is amorphous Sn of 8 nm average thickness. Photoluminescence measurements show a broad band in the 400-800 nm range. On the same growth process, SnO 2 nanoparticles and a mixture of SnO 2 rods and wires were also obtained, at 400 °C and 800 °C, respectively. INTRODUCTION SnO 2 is an n-type-semiconductor metal oxide whose bulk properties are: wide bandgap of 3.6 eV (at 300 K), low resistivity (10 -4 to 10 -6 ȍ-cm), high achievable carrier concentration (up to 6x10 20 cm -3 ), high optical transparency in the visible range, and chemical and structural stability [1,2]. Nanomaterials have mechanical, chemical, thermal, electrical, and optical properties different from those of their bulk counterparts due to the enhanced surface-volume ratio and possible quantum confinement effects [3-5]. Therefore, SnO 2 1D nanostructures are very interesting due to the various applications of SnO 2 in optoelectronic and electronic devices and as transparent conductive electrodes, catalysts, anode materials for lithium-ion batteries, and gas sensors. It is used also in field effect transistors and it has been shown to act as a sub-wavelength waveguide [4, 6-10]. EXPERIMENTAL Core-shell nanowires were synthesized by the VLS mechanism [11]. The growth process was carried out inside a horizontal reactor (a quartz tube closed at one end) which was inserted into a quartz-tube furnace. Gold, deposited as an ~150 nm thick film over Si substrates in a vacuum evaporator, was used as a catalyst and powder SnO (99.9%) as a precursor. Three substrates and an alumina crucible containing the SnO powder precursor were placed inside the reactor in such a way that, when the reactor is inserted into the furnace quartz tube, each substrate lies in a different temperature zone of the furnace and so does the precursor powder 159