Space charge limited conduction in plasma polymerized N,N,3,5 tetramethylaniline thin films

Plasma polymerized N,N,3,5 tetramethylaniline (PPTMA) thin films were deposited at room temperature by a parallel plate capacitively coupled glow discharge reactor. The current density-voltage (J-V) characteristics of PPTMA thin films of different thicknesses have been investigated at different temperatures. The J-V characteristics show two slopes at the lower and higher voltage regions. It is observed that space charge limited conduction is operative in the higher voltage region in PPTMA thin films. From the experimental studies the carrier mobility, the free carrier density, and the total trap density are found to be about 1.3 x 10(-13) m(2) V-1 s(-1), 2 x 10(21) m(-3) and 4 x 10(30) m(-3) respectively. From the Arrhenius plots of J vs. 1/T for the applied voltages 2 and 10 V, the activation energies (Delta E) are estimated to be about 0.19 +/- 0.02 and 0.85 +/- 0.05 eV in the lower and higher temperature regions respectively. At lower temperatures, the available thermal energy is not sufficient to ionize the traps, so hopping mobility is observed. While at higher temperatures, the higher values of Delta E indicate a transition from a hopping process to a distinct energy level process. (c) 2005 Elsevier B.V All rights reserved.