Quantifying the growth per cycle of ALD Al2O3 thin films on cellulosic substrates

Cellulosic products have emerged as a solution to plastics in the food packaging industry, and Al 2 O 3 deposited by atomic layer deposition (ALD) improves their barrier properties. However, the complex nature of the substrate renders reliable characterisation of thin film thickness challenging, limiting fundamental understanding of thin film growth on cellulose. Here, we present a method to determine the atomic growth per cycle (GPC) of ALD Al 2 O 3 thin films on nanocellulose substrates. Quantification was achieved by inductively coupled plasma mass spectrometry (ICP-MS) following acid digestion of the thin films. This method was found to be comparable to conventional characterisation techniques on ALD Al 2 O 3 on silicon substrate, and was subsequently applied to the nanocellulose substrates. X-Ray Fluorescence (XRF) was introduced as a complementary method to enable rapid, non-destructive measurements. A calibration curve between the proposed method and XRF enabled quantitative measurements of ALD Al 2 O 3 growth on nanocellulose substrates. The method presented in this paper revealed a higher apparent atomic GPC on nanocellulose compared to silicon substrates. This new approach provides a practical approach to quantifying thin film growth deposited on cellulosic or other complex substrates.