Tin oxide (SnO 2 ) nanowires grown by chemical vapor deposition were modified by Ar/O 2 plasma treatment through preferential etching of the lattice oxygen atoms, which produced nonstoichiometric surface compositions that imparted a manyfold higher sensitivity toward gas absorption on such surfaces. Microstructures of asgrown and plasma-treated SnO 2 nanowires confirmed the gradual change in the chemical composition and morphologies. Surficial disorder caused by the bombardment of argon and oxygen ions present in the plasma was visible as a disordered overlayer in high-resolution TEM micrographs, when compared to single crystalline as-grown SnO 2 nanowires. Gas-sensing experiments on modified SnO 2 nanostructures showed higher sensitivity for ethanol gas at lower operating temperatures and exhibited an improved transduction response toward changing gas atmospheres, attributed to the increased concentration of oxygen vacancies on the surface of SnO 2 nanowires. Modulation of surface chemistry was also supported by photoluminescence and X-ray photoemission spectroscopy studies.

Detecting small quantities of gases and chemicals is becoming increasingly important for consumer, health and security applications such as monitoring the ecological constituents, concentration control of toxic and hazardous gases. [1][2][3][4] Nanostructures are especially attractive for detector and quantifier applications, particularly due to their high surface-to-volume ratio and higher sensitivity towards surface reactions, which results in charge penetration layers being comparable to nanostructure dimensions. The signal transduction in metal oxide nanostructures based on magnitude of alteration in their electrical properties has been reported for various components, however adsorption of oxidising or reducing species and their effect on surface potential, which influences the electrical properties of semiconductor nanostructures, have been reported with mostly an optimization of their performance. [5][6][7][8][9][10][11] Tin oxide (SnO 2 ) represents the class of IV-VI compound semiconductors with a wide band gap (3.6-4.0 eV) at room temperature and intrinsic n-type electrical conductivity. [12,13] Given their low electrical resistivity (10 -2 -10 -4 Xcm), high chemical resistance, thermal stability and mechanical strength, [14] SnO 2 nanostructures offer promising potential for improved chemical sensing behaviour particularly due to the enhancement of redox reactions between different oxidation states of tin. [15] This redox switching facilitates a reversible transformation of the surface composition from Sn 4+ cations on the surface into a reduced surface with Sn 2+ cations depending on the oxygen chemical potential of the system. [16] Tin oxide nanostructures have been synthesized by a number of methods such as chemical vapor transport at high temperatures, [17,18] thermal evaporation of tin oxide powders [19] and plasma enhanced chemical vapor deposition. [20] Although a large body of data is available on the synthesis of tin oxide nanostructures (particles, films, nanowires and nanobelts) in pure and doped compositions, synthetic pathways for their controlled growth and modification remains an overarching task. We have recently reported a molecule-based chemical vapor deposition (CVD) process for the synthesis of tin oxide and other semiconductor nanowires. [21][22][23] The preformed Sn-O units in the precursor molecule [Sn(O t Bu) 4 ] and the facile and clear stripping of organic ligands resulted in single crystalline SnO 2 nanowires at relatively low temperatures. Herein we describe the controlled growth of single crystal tin oxide platelets followed by modulation of their morphology and composition induced by argon and oxygen plasma.Semiconductor oxide nanostructures with ideal stoichiometric balance (electro-neutrality) are poor transducers for chemical sensing due to low signal-to-noise ratio, making excessive signal amplifications and/or high operating temperatures mandatory for optimal sensing performance. Since electrical properties of tin oxide depend on oxygen vacancies, mobility and concent...

No abstract

No abstract

No abstract

No abstract

No abstract

No abstract