Carbon contamination mitigation for STEM imaging of chemically synthesized beam sensitive materials

Abstract

Chemically synthesized materials such as colloidal nanoparticles have been studied a lot in the past decade owing to their ease of synthesis and enhanced properties as compared to their bulk counterparts. Halide - perovskite quantum dots (h-PQDs) are one of these widely researched class of materials due to their near unity Photoluminescence Quantum Yield (PLQY). But due to the presence of organic ligands and highly ionic nature of composition, the material faces extreme carbon contamination and radiolysis damage on exposure to electron beam during Scanning Transmission Electron Microscopy (STEM) imaging and analysis. In this work, we build a methodology for atomic resolution imaging and analysis of such materials with high beam dose at room temperature. One section of the sample is exposed to stationary STEM beam which damages the exposed area of the sample while reducing contamination for the immidiately neighbouring area, thereby improving contrast and reducing astigmatism compensation and image aquisition time. The process has been optimized with different beam voltages and calculated dose rates. The resulting images appear noise free and can be analysed without any need for post processing, filters or image treatments. These results show promise in atomic resolution imaging of all chemically synthesized materials without beam damage and contrast reduction due to carbon contamination.