What is the compound name for SNO2

University of Cologne

Translated abstract:
One-dimensional (1D) metal oxide nanostructures such as B. Wires, rods, belts and tubes are the subject of intensive research in order to elucidate their various structure-property relationships, in particular with regard to their reduced dimensionality, and the possibilities of a potential scientific one or technological application. The method of chemical vapor deposition (CVD) offers good access to 1D metal oxide nanostructures through the so-called VLS mechanism (Vapor-Liquid-Solid) through the decomposition of molecular precursors in a CVD- VLS process. The present work deals with the synthesis of metal oxide nanowires in the CVD process, as well as the optimization of the reaction parameters in order to enable a directional growth of the nanostructures on substrates, and studies of physical properties for use in components. (1) Targeted synthesis, growth mechanism and plasma treatment of SnO2 nanowires. Uniform monocrystalline SnO2 nanowires could be obtained after optimizing the substrate temperature, precursor temperature, size of the catalyst particles and the angle of the substrate holder. In addition, electrical measurements, photoluminescence spectroscopy, gas sensor investigations and studies provided a deeper understanding of the physical properties of SnO2 nanowires. This work describes for the first time the directional growth of SnO2 nanowires on TiO2 (001) substrates using the molecule-based CVD method. Based on this, a growth model of the nanowires could be proposed, which is based on the interaction of the different crystallographic levels (substrate / nanowire). Both electrical and gas sensor measurements on individual SnO2 [101] nanowires showed that aligned nanowires react differently to gas molecules depending on their respective diameter and their alignment, which could be used for future gas sensors. The surface modification of SnO2 nanowires in an argon-oxygen (Ar / O2) plasma led to a reduction in the oxygen concentration in the surface of the nanowires, whereupon a non-stoichiometrically composed layer was formed, which in turn led to higher sensitivity and better dynamics at the same time Lower temperatures compared to ethanol resulted in gas sensor measurements. (2) Novel SnO2 Heterostructures: Synthesis and Properties New heterostructures (such as SnO2 @ TiO2, SnO2 @ SnO2, SnO2 @ VOx and SnO2 @ CdS) were produced by chemical surface modification of SnO2 SnO2 nanowires in a two-step CVD process. A structural characterization of SnO2 / TiO2 core-shell structures showed that mixed phases with the composition SnxTi1-xO2 (x = 0.857 ~ 1.0) are formed depending on the sintering temperature. The excellent electrical properties of SnO2 / TiO2 core-shell structures enable such structures to be used in nanowire gas sensors. SnO2 @ SnO2 heterostructures have superhydrophobic properties with a contact angle (CA) of 133 °, while simple SnO2 nanowires with a contact angle of 3 ° form superhydrophilic surfaces. A switchable surface wettability of SiOx-coated SnO2 @ SnO2 heterostructures (CA = 155.8 °) was observed when changing from UV radiation to darkness and O2 treatment. The geometric microstructure of the nanowires was the main reason for the switchable wettability from superhydrophilic to superhydrophobic surface. SnO2 @ CdS heterostructures were produced by an infiltration coating (chemical bath deposition, CBD) with the hydroxide cluster growth mechanism, and showed a significant improvement in photoconductivity compared to uncoated SnO2 nanowires in the wavelength range less than 450 nm. The work presented here was supported by the Federal Ministry of Education and Research (BMBF) financed as part of the "BMBF-NanoFutur" funding program (FKZ 03X5512).German