The incorporation of new coating technologies is complicated by the systematic generation of residual stresses, which are challenging to assess and can affect performances. A fast and reliable measurement technique could considerably speed up the development of cutting-edge glass products and reduce their cost.

In this work, the applicability of two techniques based on focused ion beam (FIB) milling and digital image correlation (DIC) to thin-films on glass has been investigated. Double-slot/ring-core FIB-DIC and cantilever ion-beam layer removal (ILR) were applied to Al-doped ZnO, Nb₂O₅ and F-doped SnO₂ coatings deposited on Si wafers and glass substrates. Multi-reflection sin²(ψ) grazing-incidence X-ray diffraction (GIXRD) was also applied for comparison.

All three techniques showed similar depth profiles, with tensile stress at the coating surface, changing to compressive within the film and reaching a maximum near the coating/substrate interface. For an AZO film, both XRD and FIB-DIC gave an average stress of -0.39±0.02 GPa and a maximal compressive value of -0.86±0.01 GPa, while a stress gradient of -1.95±0.03 GPa/μm was observed for the Nb₂O₅ at depths between 0.15 and 0.42 μm. Variations up to an order of magnitude were observed with the three techniques, which is understandable considering the different analysis depths and methodologies employed. Applying FIB-DIC over smaller areas of interest led to significant levels of noise due to ion-beam damage. However, stress alternations detected at the FTO layer interfaces matched those observed with cantilever ILR. The ILR depth resolution was also improved around the interfaces down to a few nanometres.

Due to the novelty and challenges of this project, guidelines enabling practical use of the FIB-based methods for coatings on non-conducting glass substrates have been compiled. Promising results were obtained but more work is required to make them viable for the glass industry, the main challenges being ion-beam-induced damage and charge build-up.