Single-atom vibrational spectroscopy in the scanning transmission electron microscope

Abstract

Single-atom impurities and other atomic-scale defects can notably alter the local vibrational responses of solids and, ultimately, their macroscopic properties. Using high-resolution electron energy-loss spectroscopy in the electron microscope, we show that a single substitutional silicon impurity in graphene induces a characteristic, localized modification of the vibrational response. Extensive ab initio calculations reveal that the measured spectroscopic signature arises from defect-induced pseudo-localized phonon modes—that is, resonant states resulting from the hybridization of the defect modes and the bulk continuum—with energies that can be directly matched to the experiments. This finding realizes the promise of vibrational spectroscopy in the electron microscope with single-atom sensitivity and has broad implications across the fields of physics, chemistry, and materials science.

Atomic engineering of single-atom nanozymes for enzyme-like catalysis

“…For instance, complexing the single-atoms to functional organic ligands (such as porphyrin, pyridine, imidazole and sulfydryl groups) and coordinatively unsaturated metal nodes of MOFs, or conning the singleatoms to metal defect sites and non-metallic vacancies (such as N, O, S, and C vacancies) of transition-metal compounds to guarantee the stabilization and denition of the atomic active sites of SAzymes can be carried out. [81][82][83] Secondly, the SAzyme categories with different coordination structures and enzymelike properties need to be extended, which largely depend on the central metal atoms and neighboring atoms. 61,84 However, most reported SAzymes were metal-nitrogen active sites derived from the uncontrollable pyrolysis of metal-organic complexes.…”

Defect Engineering of Molybdenum-Based Materials for Electrocatalysis

“…Ou et al characterized the molybdenum sulfide quantum dots by using a high-angle annular dark field scanning transmission electron microscope (HAADF-STEM), in which a variety of defects such as atomic vacancies, lattice distortion, and lattice fragmentation at the edges could be observed( Figure 5e) [51]. Similarly, STEM and energy dispersive spectroscopy (EDS) or STEM and EELS are usually used in combination to further analyze the elemental distribution and single-atom defects in the material [66]. For example, Kwon et al used EELS to identify Co atoms exclusively in the MoS 2 nanosheets and only Ru atoms in the Ru nanoparticles ( Figure 5i).…”

Isotope-Resolved Electron Energy Loss Spectroscopy in a Monochromated Scanning Transmission Electron Microscope

“…Furthermore, one can take advantage of different types of scattering mechanisms to access different parts of the vibrational response, as shown in Figure 1. One can collect electrons that are scattered out to high angles to primarily access highly localized impact scattering losses (Figure 2a), which enable phonons to be measured with atomic resolution [16,17] and even the direct measurement of single-atom vibrational modes [18]. Alternatively, the beam can also interact with the dipole moments in the sample and excite optical phonons, leading to delocalized dipole scattering (Figure 2b), enabling efficient excitation even when the electron beam passes tens of nanometers away from the sample in an "aloof " scattering geometry [10,12,19,20].…”