Height-resolved quantification of microstructure and texture in polycrystalline thin films using TEM orientation...

Understanding microstructure and texture in polycrystalline thin films remains a challenge. Prior research has shown that cross-section transmission electron microscopy (TEM) samples often suffer from grain overlap, reducing mapping accuracy. Plan-view samples have been proposed to improve statistics and reduce overlap. However, no prior work had resolved how to scale orientation mapping across film thickness. This gap motivated the development of new specimen preparation methods. Existing methods lack the ability to correlate in-plane and out-of-plane grain properties. No prior work had demonstrated such large-scale orientation mapping in thin films. Researchers have proposed various imaging techniques, but none provided quantitative data on grain size and orientation as a function of height. This uncertainty drove the need for a method that combines automated orientation mapping with spatial correlation.

The study aimed to develop a method for height-resolved quantification of microstructure and texture in polycrystalline thin films. The specific problem addressed was the inability to map grain properties across film thickness with high statistical accuracy. The motivation came from the need to improve growth model validation. The goal was to combine orientation mapping with a double-wedge specimen preparation method. The study sought to demonstrate this approach on ZnO thin films deposited via metal-organic chemical vapor deposition. The objective was to measure grain size, orientation, and misorientation distributions as a function of height above the substrate. The study also aimed to correlate orientation data with microstructural images. Finally, the purpose was to use the data to guide further TEM studies.

The method involved in-plane automated crystal orientation mapping in transmission electron microscopy. Cross-section and plan-view samples were prepared to compare mapping accuracy and statistical sampling. A double-wedge specimen preparation technique was used to create large-area plan-view samples. Orientation mapping was performed on ZnO thin films deposited via low-pressure metal-organic chemical vapor deposition. Over 10,000 grains were analyzed to determine size, orientation, and misorientation distributions. The data were analyzed as a function of height above the substrate. Microstructural images were correlated with orientation data to assess grain shapes and sizes. The spatial correlation of the data set was used to identify growth mechanisms such as renucleation or preferred misorientations.

The results showed that plan-view samples reduced grain overlap and improved statistical sampling compared to cross-sections. The double-wedge method enabled large-area plan-view orientation mapping across film thickness. Over 10,000 grains were measured, providing grain size, orientation, and misorientation distributions as a function of height. The data revealed spatial correlations between grain orientation and in-plane/out-of-plane shapes. Previously unnoticed growth mechanisms, such as renucleation and preferred misorientations, were identified. The orientation data were directly linked to microstructural images for correlation. The dataset guided targeted studies using nano-beam diffraction. Coherent [21̄1̄0]/(011̄3) twin boundaries were validated through site-specific nano-beam diffraction.

The study demonstrated a method for height-resolved quantification of microstructure and texture in polycrystalline thin films. The double-wedge method enabled large-area plan-view orientation mapping with improved statistical accuracy. The data provided grain size, orientation, and misorientation distributions as a function of height. The spatial correlation of the dataset revealed growth mechanisms like renucleation and preferred misorientations. The orientation data were directly linked to microstructural images for analysis. The dataset was used to guide targeted TEM studies, such as nano-beam diffraction. The method allows for quantitative assessment of growth models and simulations. The findings suggest that plan-view orientation mapping improves the reliability of microstructural analysis in thin films.