HAADF-STEM image analysis for size-selected platinum nanoclusters.

Abstract

In this study, size-selected platinum (Pt) nanoclusters were imaged with aberration-corrected scanning transmission electron microscopy in high-angle annular dark field (HAADF) mode. For image analysis, a relatively simple macro program was developed by making the use of existing ImageJ plug-ins. The macro allows effectively for assessing criterions chosen for intensity threshold and filter blurring factors. It can extract the integrated HAADF intensity, peak intensity and projected area of the clusters. Here, the effects of magnification and objective lens defocus on nanocluster measurement were investigated. It was found that the integrated HAADF intensity of Pt clusters is a more robust sample descriptor than the peak intensity and the projected area. The macro program developed is freely available. LAY DESCRIPTION: Measuring precisely the size of nanoclusters plays an important role in the investigation of nanocluster-based material systems. Aberration-corrected scanning transmission electron microscopy (STEM) is one of the most powerful tools to extract the size of clusters directly from their images. In this study, we developed a macro program based on existing ImageJ plug-ins, allowing easy-assessment of criterions chosen for image intensity threshold and filter blurring factors. It can be used to extract the integrated intensity, peak intensity, and projected area of the clusters for size determination. Using the program, we investigated the effects of magnification and objective lens defocus on measurements performed on size-selected platinum (Pt) nanoclusters, and found that the integrated intensity of Pt clusters is a more robust sample descriptor than the peak intensity and the projected area. The macro developed allows a rapid assessment of factors affecting the accuracy with which size information can be obtained from clusters.