Nanoscale Imaging of Infrared Plasmons with Monochromated STEM-EELS

Electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) has undergone significant improvement in energy resolution, making it a suitable tool for studying plasmons in the infrared energy range. In this talk, I will present infrared plasmons in conducting oxides studied by monochromated STEM-EELS. I will first discuss the excitation of surface and bulk plasmon modes in Sn-doped In₂O₃ freestanding film, which is achieved through the interference of surface plasmon polaritons near the film edge [1]. I will then demonstrate tunable infrared plasmons in La-doped BaSnO₃ nanocrystals with varying sizes and shapes [2, 3]. Highlight of the talk will be given to imaging a BaSnO₃ nanocrystal with doping inhomogeneity, where a plasmon mode confined between regions with varying doping was revealed. These results showcase the unique advantages of monochromated EELS in exploring infrared plasmonics.

References:
[1] H. Yang, et al. Phys. Rev. B, 102:205427, 2020
[2] H. Yang, et al. Small, 18, 210689, 2022
[3] H. Yang, et al. ACS Nano, 16(11), 18795-18805, 2022