Structural and Optical Characterization of ...

Plasma Polymerized Pyrrole (PPPy) thin films of different thicknesses have been deposited onto glass substrates at room temperature by using a capacitively coupled parallel plate reactor. Fourier Transform Infrared (FTIR) and Ultraviolet-visible (UV-Vis) spectroscopy techniques have been used to characterize the as-grown thin films of about 400, 450 and 500 nm thickness. The structural analyses by means of FTIR spectroscopy have indicated that the monomer has undergone the re-organization and the ring structure has been retained during the plasma polymerization. From the UV-Vis absorption spectra, allowed direct transition (Eqd) and indirect transition (Eqi) energy gaps were determined. The Eqd for 400, 450 and 500 nm thick PPPy films were found to be 3.25, 3.47, and 3.58 eV respectively. On the other hand, the Eqi for the same series are 2.22, 2.25, and 2.35 eV respectively. From these results, it is seen that both the Eqd and Eqi are declined with the decrease in the thicknesses of the films, which is an indication of decreasing the resistivity of the film with lower thickness. This result would in turn cause an increase in electrical conductivity in the low-thickness thin film.