PEALD of SiO₂ and Al₂O₃ Thin Films on Polypropylene: Investigations of the Film Growth at the Interface, Stress, and Gas Barrier Properties of Dyads

Abstract

A study on the plasma-enhanced atomic layer deposition of amorphous inorganic oxides SiO and AlO on polypropylene (PP) was carried out with respect to growth taking place at the interface of the polymer substrate and the thin film employing in situ quartz-crystal microbalance (QCM) experiments. A model layer of spin-coated PP (scPP) was deposited on QCM crystals prior to depositions to allow a transfer of findings from QCM studies to industrially applied PP foil. The influence of precursor choice (trimethylaluminum (TMA) vs [3-(dimethylamino)propyl]-dimethyl aluminum (DMAD)) and of plasma pretreatment on the monitored QCM response was investigated. Furthermore, dyads of SiO/AlO, using different Al precursors for the AlO thin-film deposition, were investigated regarding their barrier performance. Although the growth of SiO and AlO from TMA on scPP is significantly hindered if no oxygen plasma pretreatment is applied to the scPP prior to depositions, the DMAD process was found to yield comparable AlO growth directly on scPP similar to that found on a bare QCM crystal. From this, the interface formed between the AlO and the PP substrate is suggested to be different for the two precursors TMA and DMAD due to different growth modes. Furthermore, the residual stress of the thin films influences the barrier properties of SiO/AlO dyads. Dyads composed of 5 nm AlO (DMAD) + 5 nm SiO exhibit an oxygen transmission rate (OTR) of 57.4 cm m day, which correlates with a barrier improvement factor of 24 against 5 when AlO from TMA is applied.

From Precursor Chemistry to Gas Sensors: Plasma‐Enhanced Atomic Layer Deposition Process Engineering for Zinc Oxide Layers from a Nonpyrophoric Zinc Precursor for Gas Barrier and Sensor Applications

“…Another probable reasoning, might be the intrinsic film stress which for example changes from compressive stress, thereby closing possible defects, to tensile stress or a reduced compressive stress as already shown for SiO 2 barrier layers of different thicknesses in our earlier studies. [ 67 ] Of course, for the ZnO layers obtained herein, this needs to be proven and is currently under investigation. However, the barrier performance is in the same range as the OTR of equivalently thick Al 2 O 3 layers on PET, as shown earlier for the same polymer substrates, [ 49,50 ] rendering the ZnO layers to be applicable as transparent gas barrier layers (GBLs).…”

Janus Membranes via Diffusion‐Controlled Atomic Layer Deposition

“…Oxygen plasma has been shown by X‐ray photoelectron spectroscopy (XPS) to incorporate oxygen‐containing functional groups along poly(propylene)'s hydrocarbon backbone . These pretreatments increase the nucleation rate of Al 2 O 3 ALD by creating reactive sites where TMA chemisorbs on the polymer surface …”

Investigation of an atomic‐layer‐deposited Al2O3 diffusion barrier between Pt and Si for the use in atomic scale atom probe tomography studies on a combinatorial processing platform

“…It was produced by PEALD 23 in a custom-built, hot-wall stainless-steel reactor chamber (20 cm  20 cm  20 cm) with a top-to-bottom flow geometry facilitating precursor and gas transport. Further details on the PEALD process are presented in the supporting information.…”