The Effect of Nanoparticle Surface State on Trap Level Distribution of Polyimide/Aluminum Nitride-montmorillonite Nanocomposite Films

Abstract

The electrical properties of polyimide (PI) nanocomposites, which are widely used in microelectronic industry and electrical engineering fields, strongly depend on the surface state of nanoparticles. To explore this dependence, the aluminum nitride (AIN) nanoparticles were treated by γ-aminopropyltriethoxysilane coupling agent, while PI/MMT, PI/AlN, and PI/AlN-MMT nanocomposite films doped by 5 wt% of treated and untreated AlN nanoparticles were prepared by the in-situ polymerization process. The SEM and TEM results indicate that the untreated AlN nanoparticles are prone to accumulation in the polymer matrix, while those treated by the coupling agent are readily combined with the polyimide matrix, and their compatibility and dispersion exhibit a significant improvement. The trap level distributions of nanocomposite films were studied by the isothermal discharge current (IDC) method based on the charge decay theory linking IDC with the trap level density (TLD). The TLD and number of trapped charges of PI/AlN and PI/AlN-MMT films doped by treated AlN nanoparticles are found to be much higher than those of untreated ones. The TLD of the PI/AlN (treated) film is 6.490×1023 eV·m-3, which is about 2.27 times higher than that of pure PI film in the range of 0.9~1.1 eV, while the maximum TLD=9.370×1023 eV·m-3 is observed in the PI/AlN (treated)-MMT film.