Electrical and optical properties of plasma-polymerized N, N,3,5-tetramethylaniline thin films

Plasma polymerization is a versatile and important technique for depositing uniform, pinhole-free and flawless thin films of organic materials. So plasma-polymerized N,N,3,5-tetramethylaniline (PPTMA) thin films were deposited onto glass substrates at room temperature by a capacitively coupled plasma polymerization system using TMA as a precursor. Infrared spectroscopy, elemental analysis and UV-visible (UV-vis) spectroscopy reveal that there are conjugations in the matrix of the PPTMA thin films. From UV-vis spectroscopy it is found that indirect energy gap varies from 1.49 to 1.86 eV with film thickness. Current density-voltage characteristics indicate that the conduction mechanism in PPTMA thin films is space charge-limited conduction (SCLC). The activation energies in the SCLC region are 0.21 ± 0.05 and 0.93 ± 0.08 eV at lower and higher temperature regions respectively. Electrical and optical measurements suggest that the top of valance band and the bottom of the conduction band may have gap states and the middle of the energy gap may be equal to the high-temperature activation energy