Photosensitivity activation of SnO2 thin film gas sensors at room temperature

Camagni, P.; Faglia, G.; Galinetto, P.; Perego, C.; Samoggia, G.; Sberveglieri, Giorgio

doi:10.1016/0925-4005(96)80023-2

Cited by 103 publications

(48 citation statements)

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“…Inspired by the excellent photoconduction and light-enhanced chemical sensing properties of SnO 2 bulk materials, [6] we have further studied the UV response of our SnO 2 nanowire transistors described above, and a strong modulation of the conductance by UV illumination was observed. Our experiment involved a UV lamp of 254 nm in wavelength fixed at a distance of approximately 2 cm away from the nanowire transistor, which was kept under practical conditions, i.e., in air, at room temperature, and under indoor incandescent light during the measurements.…”

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confidence: 95%

“…SnO 2 is known to be a non-stoichiometric n-type semiconductor in the bulk form due to the O 2 deficiency. [6] We have made SnO 2 nanowire FETs based on our successful synthesis. A degenerately doped silicon wafer covered with 500 nm SiO 2 was used as the substrate, on which SnO 2 nanowires of 20 nm in diameter were deposited.…”

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confidence: 99%

“…Among them, SnO 2 is particularly interesting and has many important applications. For instance, SnO 2 is a very important n-type semiconductor with a large bandgap (E g = 3.6 eV at 300 K [6] ), thus making it ideal to work as transparent conducting electrodes for organic light emitting diodes and solar cells. [7±9] In addition, SnO 2 thin films have been extensively studied and used as chemical sensors for environmental and industrial applications.…”

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Laser Ablation Synthesis and Electron Transport Studies of Tin Oxide Nanowires

et al. 2003

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One-dimensional metal oxide nanowires, such as In 2 O 3 , [1] ZnO, [2] SnO 2 , [3] CdO, [4] and CuO [5] nanowires, have attracted a lot of attention because of their unique properties for applications ranging from nanoelectronic devices to gas sensors. Among them, SnO 2 is particularly interesting and has many important applications. For instance, SnO 2 is a very important n-type semiconductor with a large bandgap (E g = 3.6 eV at 300 K [6] ), thus making it ideal to work as transparent conducting electrodes for organic light emitting diodes and solar cells. [7±9] In addition, SnO 2 thin films have been extensively studied and used as chemical sensors for environmental and industrial applications.[7±9] SnO 2 in the nanowire form has enormous potential to work as building blocks for nanoelectronics, and is also expected to offer superior chemical sensing performance due to the enhanced surface to volume ratio. Despite the utmost importance, only a relatively small effort has been directed toward the synthesis of SnO 2 whiskers, nanorods, and more recently nanobelts. [3,10±12] Much is left to be explored, especially for the synthesis of high-quality, single-crystalline SnO 2 nanowires with precisely controlled diameters below 30 nm, as required for high-performance field-effect nanowire transistors. In this paper, we report an efficient and reliable laser-ablation approach for large-scale synthesis of SnO 2 nanowires. Precise control over the nanowire diameters has been achieved by using monodispersed gold clusters as the catalyst. Detailed material analysis, such as transmission electron microscopy (TEM) and X-ray diffraction (XRD), were used to confirm the single-crystalline nature of our nanowires. In addition, field effect transistors (FETs) have been constructed based on individual SnO 2 nanowires with on/off ratios up to 10 3 . These nanowire transistors were further demonstrated to work as sensitive UV and polarized UV detectors.A quartz tube furnace was used for our SnO 2 synthesis, where a pure Sn target was placed at the upper-stream of the tube outside the hot zone of the furnace, and Si±SiO 2 substrates covered with 20 nm gold catalytic clusters were placed in the middle of the quartz tube. The tube was then purged with 0.02 % oxygen diluted in argon, followed by heating of the furnace to 900 C. The Sn target was then ablated with a Nd:YAG laser to supply Sn vapor, which was carried downstream by the oxygen±argon mixture. The chamber was maintained at 400 torr during the laser ablation, and the typical reaction time used was about 10±30 min. Our synthesis follows the well-known vapor±liquid±solid (VLS) growth mechanism, where the Sn vapor first diffuses into the gold catalytic particles, and grows out and reacts with O 2 to form SnO 2 once the Sn±Au alloy reaches supersaturation. Continued addition of Sn into the Sn±Au nanoparticle feeds the SnO 2 growth and eventually the diameter of the SnO 2 nanowire is directly linked to the catalytic particle size. After cooling down, the samples were characteriz...

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Laser Ablation Synthesis and Electron Transport Studies of Tin Oxide Nanowires

et al. 2003

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“…Under UV illumination and at room temperature, these nanomaterials display a reversible response towards oxidizing gases which was not observed in dark conditions. According to previously reported models [25], UV illumination desorbs NO 2 molecules and oxygens from the metal oxide surface leading to partially reduced surfaces [26,27]. In this situation, NO 2 molecules and oxygens in air compete for the same adsorption sites (which are light-induced surface oxygen vacancies, according to first principles calculations [28][29][30]).…”

Section: Resultsmentioning

confidence: 99%

Shrinkage Effects of the Conduction Zone in the Electrical Properties of Metal Oxide Nanocrystals: The Basis for Room Temperature Conductometric Gas Sensor

et al. 2009

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The influence of charge localized at the surface of minute metal oxide nanocrystals was studied in WO 3 and In 2 O 3 nanostructures, which were obtained replicating mesoporous silica templates. Here, it is shown that the very high resistive states observed at room temperature and dark conditions were originated by the total shrinkage of the conductive zone in the inner part of these nanocrystals. On the contrary, at room temperature and under UV illumination, both photogenerated electron-hole pairs and empty surface states generated by photons diminished the negative charge accumulated at the surface, enlarging the conductive zone and, as a consequence, leading to a reduction of the electrical resistance. Under these conditions, empty surface states produced by UV light reacted with oxidizing gaseous molecules. The charge exchange associated to these reactions also affected the size of the inner conductive zone, and leaded to a new steady-state resistance. These chemical, physical and geometrical effects can be used for gas detection, and constitutes the basis for developing novel room temperature conductometric gas sensors responsive to oxidizing species.

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“…By changing the occupancy of the defects by electrons and holes, illumination could change the concentration of the adsorption centers of each given type and the capacity of adsorption on the surface of the semiconductor [18]. Therefore, UV-light excitation could play an important role in improving the gas-sensing property of the sensors [18][19][20].…”

Section: Introductionmentioning

confidence: 99%