SYNTHESIS OF NANOWIRE NETWORKS FOR CHEMICAL GAS SENSOR APPLICATIONS A.Jishiashvili Institute of Cybernetics. Georgian Technical University.

2 nm micrometer

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The purpose of this work: to synthesize the NW network using the new pyrolytic growth technology; to study the performance of fabricated gas sensor. 4

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6 InP core Ga 2 O 3 shell

7 Schematic of the experimental arrangement for the growth of In 2 O 3 nanowires Dependence of source temperature on the applied power Dependence of source temperature on time

In 2 O(g) + 2H 2 O(g) = In 2 O 3 + 2H 2 (g) ΔG= - 200kJ In 2 O(g) + H 2 (g) = 2In + H 2 O(g) ΔG= kJ XRD pattern of In 2 O 3 nanowires(a); SEM images of tapered nanowires grown at 420°C (b-d). 8

9 SEM images of nanowires (a-c); Energy Dispersive X-Ray pseudo- color images of nanowires grown at 420 °C (e-d).

10 a b c SEM image of nanowires grown at 470ºC (a); High Resolution TEM image of VLS grown In2O3 nanowires (b) and corresponding SAE pattern.

11 O 2 +e - O – 2(ads) O – 2(ads) +e – 2O – (ads) 2NH 3 +3O - (ads) N 2 +3H 2 O+3e - Fabricated In 2 O 3 nanowire network based gas sensor Ti/Au contact layers Oxygen mediated mechanism of NH 3 sensing

12 Variation of sensitivity with concentration of ammonia for In 2 O 3 nanowire-based sensor at 300°C Gas sensing characteristics of In 2 O 3 nanowires for 800 ppm of ammonia at different temperatures Permissible exposure limit for ammonia is 35 ppm (Occupational Safety and Health Administration)

The results of this study demonstrate that : developed new pyrolytic technology may be successfully used for producing In 2 O 3 nanowires; gas sensor fabricated on the base of In 2 O 3 nanowire network can be used for detecting 10 ppm level of ammonia. 13

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