Ptychography is a diffraction imaging method that allows one to solve inverse problems in microscopy with the ability to retrieve information about and correct for systematic errors. Here, we propose techniques to correct for axial position uncertainty, detector point spread, and inhomogeneous detector response using ptychography's inherent self-calibration capabilities. The proposed methods are tested with visible light and x-ray experimental data. We believe that the results are important for precise calibration of ptychographic experimental setups and rigorous quantification of partially coherent beams by means of ptychography.

Atomic layer deposition (ALD) is an enabling technology for encapsulating sensitive materials owing to its high-quality, conformal coating capability. Finding the optimum deposition parameters is vital to achieving defect-free layers; however, the high dimensionality of the parameter space makes a systematic study on the improvement of the protective properties of ALD films challenging. Machine-learning (ML) methods are gaining credibility in materials science applications by efficiently addressing these challenges and outperforming conventional techniques. Accordingly, this study reports the ML-based minimization of defects in an ALD-Al 2 O 3 passivation layer for the corrosion protection of metallic copper using Bayesian optimization (BO). In all experiments, BO consistently minimizes the layer defect density by finding the optimum deposition parameters in less than three trials. Electrochemical tests show that the optimized layers have virtually zero film porosity and achieve five orders of magnitude reduction in corrosion current as compared to control samples. Optimized parameters of surface pretreatment using Ar/H 2 plasma, the deposition temperature above 200 °C, and 60 ms pulse time quadruple the corrosion resistance. The significant optimization of ALD layers presented in this study demonstrates the effectiveness of BO and its potential outreach to a broader audience, focusing on different materials and processes in materials science applications.

In many applications of copper in industry and research, copper migration and degradation of metallic copper to its oxides is a common problem. There are numerous ways to overcome this degradation with varying success. Atomic layer deposition (ALD) based encapsulation and passivation of the metallic copper recently emerged as a serious route to success owing to the conformality and density of the ALD films. So far, the majority of the studies have been focused on corrosion protection of copper in a variety of chemical environments, mostly at ambient temperature. An investigation of the stability of the ALD film stacks and copper’s interaction with them at elevated temperatures has been lacking. Here, we study the mitigation of copper oxidation and migration in 50 nm thick Al2O3/TiO2 and Al2O3/SiO2 bilayer ALD stacks. First, the corrosion dynamics were investigated via in situ X-ray diffraction (XRD) at 350 °C under atmospheric conditions, and second, the interaction of copper with the passivation layers have been examined post factum using detailed spectro-microscopic investigations. According to the XRD results, both ALD films exhibited excellent oxidation protection. In contrast, bare Cu immediately started to oxidize at 350 °C and transformed entirely to its known oxide phases in 4 h. Spectro-microscopic studies revealed that there are structural and chemical changes on the top surface and within the film stacks. The TiO2 layer was crystallized during annealing, while the SiO2 layer stayed in the amorphous phase, which was analyzed by grazing incidence XRD and transmission electron microscopy. According to scanning electron microscopy and X-ray photoelectron spectroscopy analysis, copper was detected on the surface with a higher amount in Al2O3/TiO2 than Al2O3/SiO2, 5.2 at.% and 0.7 at.%, respectively. Based on the surface and cross-sectional analysis, copper migration was observed on both layers, albeit more substantially in Al2O3/TiO2. In the case of Al2O3/SiO2, the bulk of the copper was captured at the interface of the two oxides.