Electrical conduction and tailored electrical properties of plasma polymerized 2-(diethylamino) ethyl methacrylate and N,N,3,5 tetra-methylaniline bilayer thin films for optoelectronics

Bilayer plasma polymerized (PP) thin films of 2-(diethylamino) ethyl methacrylate (DAEM) and N,N,3,5 tetra-methylaniline (TMA) are deposited with varying deposition time ratios using a capacitively coupled glow discharge plasma reactor. A smoother, more homogeneous and pinhole free bilayer films is observed compared to the single layer film. The presence of characteristic C=O, C−N, and aromatic C−H vibration modes indicate effective molecular integration and possible crosslinking within the bilayer structure, providing strong evident of a chemically stable and structurally coherent polymer network. The Al/ PP(DAEM-TMA)/Al structure shows Ohmic behavior at low voltages (0.5 − 10 V) and non-Ohmic conduction at higher voltages (11 − 100 V). Thickness dependent bilayer films exhibit space-charge-limited conduction, indicating charge transport controlled by a discreate trap distribution. With decreasing the proportion of DAEM in the bilayer structure, the trap density and carrier mobility decrease, while the free carrier density increases, indicating enhanced carrier trapping and reduced charge transport efficiency in thicker films. The AC conductivity increase with frequency and decrease with film thickness, suggesting non-Debye-type relaxation, as further confirmed by the Cole-Cole plots, while the higher current density in thinner films governed by the formation of localized sates. At low temperatures, the activation energy ranges from 0.31 to 0.39 eV, whereas at the high temperature regions, these values increase with the increasing DAEM deposition time in the bilayer structure, reaching up to 0.60 eV, suggesting the involvement of deeper trap states associated with carbonyl (C=O) groups and interfacial defects in PP(DAEM-TMA) bilayer thin films. These results suggests that PP(DAEM-TMA) films could serve as an insulating layer in manufacturing optoelectronic and electronic devices.