Effect of iodine doping on the ac electrical properties of plasma polymerized 2(diethylamino)ethyl methacrylate thin films

摘要

Plasma polymerized 2-(Diethylamino) ethyl methacrylate (PPDEAEMA) thin films were prepared through glow discharge of 2-(Diethylamino)ethyl methacrylate (DEAEMA) using a capacitively coupled reactor. The variation of ac conductivity σac with frequency from 100 Hz to 100 kHz in the temperature range from 298 to 398 K exhibits that the σ increases as frequency increases. A little variation in conductivity is observed with increasing temperature. The σac increases rapidly up to 10 Hz, after that the rate of increase become slower and then start to decrease slowly. Activation energy is found about 0.02 eV which indicates that hopping conduction mechanism is operative in iodine doped PPDEAEMA thin films. The value of dielectric constant ε' increases (in comparison to as deposited PPDEAEMA) due to iodine doping. It is seen that ε' decrease slightly upto 350 K and then there is comparatively faster decrease in ε' with the increase of frequency as like the as deposited PPDEAEMA thin films. The dielectric loss tangent, tanδ, with frequency at different temperatures (298 to 398 K) for iodine doped PPDEAEMA thin films of 100 and 200 nm thicknesses are observed which indicates that tanδ increases as the frequency increases and show some relaxation peaks at the high frequency region (>10Hz) which is shifted with temperature and indicates the presence of relaxation in iodine doped PPDEAEMA thin films. It is seen that σ, ε' and tanδ increased (in comparison to as deposited PPDEAEMA) after iodine doping, which may be due to the formation of charge transfer complexes. The addition of iodine boost up the polar character of PPDEAEMA thin films hence it becomes more electrically conductive. PPDEAEMA is proficient to form charge transfer complex which proceeds as excess of carriers/electron-hole pairs in PPDEAEMA thin films.