115 resultados para zinc ion
em Cambridge University Engineering Department Publications Database
Resumo:
Here we report on the successful low-temperature growth of zinc oxide nanowires (ZnONWs) on silicon-on-insulator (SOI) CMOS micro-hotplates and their response, at different operating temperatures, to hydrogen in air. The SOI micro-hotplates were fabricated in a commercial CMOS foundry followed by a deep reactive ion etch (DRIE) in a MEMS foundry to form ultra-low power membranes. The micro-hotplates comprise p+ silicon micro-heaters and interdigitated metal electrodes (measuring the change in resistance of the gas sensitive nanomaterial). The ZnONWs were grown as a post-CMOS process onto the hotplates using a CMOS friendly hydrothermal method. The ZnONWs showed a good response to 500 to 5000 ppm of hydrogen in air. We believe that the integration of ZnONWs with a MEMS platform results in a low power, low cost, hydrogen sensor that would be suitable for handheld battery-operated gas sensors. © 2011 Published by Elsevier Ltd.
Resumo:
Highly c-axis oriented ZnO films have been deposited at room temperature with high rates (∼50 nm·min -1) using an innovative remote plasma sputtering configuration, which allows independent control of the plasma density and the sputtering ion energy. The ZnO films deposited possess excellent crystallographic orientation, high resistivity (>10 9 Ω·m), and exhibit very low surface roughness. The ability to increase the sputtering ion energy without causing unwanted Ar + bombardment onto the substrate has been shown to be crucial for the growth of films with excellent c-axis orientation without the need of substrate heating. In addition, the elimination of the Ar + bombardment has facilitated the growth of films with very low defect density and hence very low intrinsic stress (100 MPa for 3 μm-thick films). This is over an order of magnitude lower than films grown with a standard magnetron sputtering system. © 2012 American Institute of Physics.
Resumo:
Highly transparent zinc oxide (ZnO) nanowire networks have been used as the active material in thin film transistors (TFTs) and complementary inverter devices. A systematic study on a range of networks of variable density and TFT channel length was performed. ZnO nanowire networks provide a less lithographically intense alternative to individual nanowire devices, are always semiconducting, and yield significantly higher mobilites than those achieved from currently used amorphous Si and organic TFTs. These results suggest that ZnO nanowire networks could be ideal for inexpensive large area electronics. © 2009 American Institute of Physics.
Resumo:
This paper reports on the synthesis of zinc oxide (ZnO) nanostructures and examines the performance of nanocomposite thin-film transistors (TFTs) fabricated using ZnO dispersed in both n- and p-type polymer host matrices. The ZnO nanostructures considered here comprise nanowires and tetrapods and were synthesized using vapor phase deposition techniques involving the carbothermal reduction of solid-phase zinc-containing compounds. Measurement results of nanocomposite TFTs based on dispersion of ZnO nanorods in an n-type organic semiconductor ([6, 6]-phenyl-C61-butyric acid methyl ester) show electron field-effect mobilities in the range 0.3-0.6 cm2V-1 s-1. representing an approximate enhancement by as much as a factor of 40 from the pristine state. The on/off current ratio of the nanocomposite TFTs approach 106 at saturation with off-currents on the order of 10 pA. The results presented here, although preliminary, show a highly promising enhancement for realization of high-performance solution-processable n-type organic TFTs. © 2008 IEEE.
Resumo:
The properties of amorphous carbon (a-C) deposited using a filtered cathodic vacuum arc as a function of the ion energy and substrate temperature are reported. The sp3 fraction was found to strongly depend on the ion energy, giving a highly sp3 bonded a-C denoted as tetrahedral amorphous carbon (ta-C) at ion energies around 100 eV. The optical band gap was found to follow similar trends to other diamondlike carbon films, varying almost linearly with sp2 fraction. The dependence of the electronic properties are discussed in terms of models of the electronic structure of a-C. The structure of ta-C was also strongly dependent on the deposition temperature, changing sharply to sp2 above a transition temperature, T1, of ≈200°C. Furthermore, T1 was found to decrease with increasing ion energy. Most film properties, such as compressive stress and plasmon energy, were correlated to the sp3 fraction. However, the optical and electrical properties were found to undergo a more gradual transition with the deposition temperature which we attribute to the medium range order of sp2 sites. We attribute the variation in film properties with the deposition temperature to diffusion of interstitials to the surface above T1 due to thermal activation, leading to the relaxation of density in context of a growth model. © 1997 American Institute of Physics.
Resumo:
Controlling the growth of ZnO nanostructures for photovoltaic applications will ensure greater device efficiency and parameter control. This paper reports on methods to engineer the morphology and tailor the nanostructure growth direction through the hydrothermal synthesis method. Effective control is achieved through the use of a sputtered zinc layer together with modifications of the growth solution. These nanostructures have been developed with a view to incorporation into excitonic solar cells, and methods to improve surface stability using a fully aqueous synthesis method will be discussed. © by Oldenbourg Wissenschaftsverlag, München.