Phys.org March 31, 2023
Applying strong DC electric fields on the apex of a sharp metallic tip causes electrons to be emitted radially from the apex to vacuum magnifying the nanoscopic information on the apex, which serves as a field emission microscope (FEM). When depositing molecules on such a tip, peculiar electron emission patterns such as clover leaves appear. However, the source of these emission patterns has not yet been identified owing to the limited experimental information about molecular configurations on a tip. An international team of researchers (Japan, Germany, France) used fullerene molecules and characterized the molecule-covered tip by an FEM. In addition to the experiments, they performed simulations to obtain optimized molecular configurations on a tip. Both results indicated that the molecules, the source of the peculiar emission patterns, appeared on a molecule layer formed on the tip under strong DC electric fields. Furthermore, the simulations revealed that these molecules were mostly isolated single molecules forming single-molecule-terminated protrusions. Upon the excellent agreements in both results, the researchers concluded that each emission pattern originated from a single molecule. According to the researchers their work should pave the way to revive old-fashioned electron microscopy as a powerful tool for investigating a single molecule… read more. Open Access TECHNICAL ARTICLE  1 , 2 Â
Experimental setup and typical FEM images of molecules… Credit: Scientific Reports, 12, Article number: 2714 (2022)Â