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The main goal of the present study is to optimize the morphology of the VOC sensor to develop a stable system with good reversibility and optimum sensitivity. For VOC sensors based on polymer/metal composites, the morphology of the clusters, the cluster size and density principally affects the sensing property. And the morphology of clusters is a function of method of production and process parameters. So, the fundamental question is which method of production at which parameters give rise to a highly sensitive and stable sensor with ability to recover upon unloading. To answer these questions, we take a model polymer PMMA and deposit Au clusters on it and start optimizing all the necessary parameters for producing a stable and reversible VOC sensor. From organic deposition techniques, we chose spin coating for it is cheap and highly accurate. From composite production methods, a set of samples with a wide range of conductivity were prepared by both Sputtering and thermal evaporation techniques. From sensing measurement results, it was to be known that samples prepared with thermal evaporation technique showed relatively more stable property than those prepared with sputtering technique. An in-situ measurement of current versus deposition time showed three regions of conductivity change. Based on this, we produce samples of different polymer film thickness with conductivities in the three regions:- nanoAmpere, microAmpere, and milliAmpere current regions and careful investigation of the morphology of clusters in these regions have been carried out with the Transmission Electron Microscopy (TEM).
To stabilize the metal clusters grown on top of the polymer film, the clusters were embedded up to the glass transition temperature of the polymer film with different embedding time. To prove that the sensing mechanism is the swelling phenomenon upon sorption of the gases into the polymer, a quartz measurement system was used.

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Masters Course MSS

Studiengang Materialwissenschaft