Effect of heat treatment on infrared and ultraviolet–visible spectroscopic studies of the PPnBMA thin films
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In this paper, a comparative analyses on the surface morphological, compositional, structural and optical behavior of as-deposited and heat treated plasma polymerized n-butyl metharylate (PPnBMA) thin films has been presented. Scanning electron microscopic observation exhibited that the heat-treated PPnBMA (at 473 K for 1 h) thin film surface was smoother and more compact than the as-deposited one. From energy dispersive X-ray spectra it would be predicted that carbon is present in higher proportion in heat-treated PPnBMA thin films and the presence of oxygen is lower. TGA curves display that the thermal stability increases due to heat treatment. The FTIR spectroscopic analysis signifies that absorption bands are shifted to lower or higher wavenumbers owing to heat treatment representing structural alteration due to decrease of cross-linking. The direct and indirect transition energy gaps (Egd and Egi) were evaluated from optical absorption spectra and found that the values of Egd and Egi were increasing trend with the increase of thickness for both as-deposited and heat-treated PPnBMA thin films. But for heat-treated PPnBMA thin films Egd and Egi values are decreased compared to that of as-deposited PPnBMA. The change of other optical parameters such as the extinction coefficient, Urbach energy and steepness parameter due to heat treatment were also discussed.
This work was financial supported by the Bangladesh University of Engineering and Technology (BUET). Dr. Rahima Nasrin is grateful to Professor Dr. S. M. Imamul Huq, Vice-Chancellor, University of Barisal for his generous support and inspiration to continue this research work.
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