Molecular layer deposition of Nylon 2,6 polyamide polymer on flat and particle substrates in an isothermal enclosure containing a rotary reactor

Polyamide thin films, designated Nylon 2,6, were grown on flat and particle substrates using molecular layer deposition (MLD) in a custom-built isothermal enclosure containing a rotary reactor. The polyamide films were grown using sequential exposures of ethylene diamine and adipoyl chloride. The reactor and precursors were contained in a fiberglass oven to keep all reactor components at the same temperature. A growth rate of 4.0 Å/cycle at 67 °C was determined on flat substrates with ex situ x-ray reflectivity and spectroscopic ellipsometry. The temperature dependence of the Nylon 2,6 displayed a peak growth rate at 67 °C with decreasing growth rates above and below this temperature. X-ray photoelectron spectroscopy of the polyamide film on flat substrates also revealed an elemental composition consistent with the Nylon 2,6 polymer with a small amount of chlorine in the film. The isothermal reactor allowed MLD to be performed consistently on high surface area particles at low temperatures. Transmission electron microscopy (TEM) images showed growth of the Nylon 2,6 films on ZrO₂, cellulose, and metformin particles that was consistent with the growth on witness wafers. The growth of the Nylon 2,6 films was also linear versus the number of MLD cycles. The TEM images displayed reproducible MLD growth on particles of varying size and composition. Fourier transform infrared spectroscopy and energy dispersive spectroscopy were consistent with the expected characteristics of the Nylon 2,6 polyamide film. Nylon 2,6 MLD should find application when low-temperature MLD is needed to coat thermally sensitive substrates such as organic films or pharmaceutical powders.