Molecular Layer Deposition of Thermally Stable Polybenzimidazole-Like Thin Films and Nanostructures

Abstract

The deposition of polybenzimidazole (PBI)-like thin films by molecular layer deposition is reported here for the first time using isophthalic acid (IPA) and 3,3′-diaminobenzidine (DAB) as monomers and trimethylaluminum (TMA) as a linker precursor. Two precursor pulsing sequences are tested, the ABCB (TMA + IPA + DAB + IPA) and ABC (TMA + IPA + DAB) type MLD processes result in different types of PBI-like films. With the ABCB sequence thin film growth per cycle (GPC) of 6.0 Å is obtained at 225–280 °C, whereas GPC of 7.0 Å is obtained with the ABC sequence. Films are characterized in detail by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, time-of-flight elastic recoil detection analysis, and atomic force microscopy. The films have good thermal stability and withstand annealing at 400 °C in both air and nitrogen. PBI nanostructures are prepared by depositing PBI-like film on electroblown polyvinylpyrrolidone fibers and removing the template fibers by annealing or dissolution into ethanol.