Atomic-scale identification of invisible cation vacancies at an oxide homointerface

Deep Learning‐Assisted Quantification of Atomic Dopants and Defects in 2D Materials

“…To demonstrate the improvement in atomic contrast, we compared the intensity profiles (Figure 2f,g ) extracted from the two different atomic arrays of V‐2Se and W‐Se, which are marked by the vertical dotted lines in Figure 2c–e . Since the intensity in the ADF imaging strongly shows the atomic number dependence if the crystal thickness is uniform, [ 20 , 21 ] W and 2Se atoms should exhibit stronger intensity than V or single Se. This contrast characteristic of the atom profiles is clearly observed in the denoised ADF image, whereas the accurate identification of atom positions is seldom possible in the profiles obtained from the raw image because of the significant fluctuations in intensities.…”

“…Intriguingly, the content of V dopants under continuous electron beam irradiation remained almost constant (green graph in Figure 5c ), which suggests that anions are more susceptible to the radiolysis interaction with the electron beam than cations, which is in accordance with many studies on electron beam interactions. [ 3 , 9 , 21 , 27 , 30 ] This dynamics of defect generation behavior was first revealed from the massive image dataset with the help of deep learning‐assisted quantification, which does not require data sampling to reduce the load of interpretation at the cost of accuracy.…”

Doping-Mediated Lattice Engineering of Monolayer ReS2 for Modulating In-Plane Anisotropy of Optical and Transport Properties

“…In HAADF imaging, the contrast in the resulting image is approximately scaled to the square of the atomic number ( Z ∼2 ). Hence, heavy Re atoms ( Z = 75) can be clearly captured as bright dots, whereas light S atoms ( Z = 16) are seldom detected. − The HAADF STEM image of the pristine ReS 2 (Figure a) shows a typical 1T′ structure exhibiting a rhombic array of an in-plane diamond-shaped motif (DM) composed of four Re atoms, and these Re-DMs are closely linked along the [010] direction. , This characteristic crystalline anisotropy is considered to be the basis for the direction-dependent electrical properties, because the diamond chains (DCs) connecting neighboring DMs contribute as conducting pathways . The FFT pattern of the whole HAADF image shows a result corresponding to the simulated diffraction pattern of the [001] oriented ReS 2 (Figure c).…”

“…In addition to the formation of nanodomains, structural distortion of the lattice or the formation of structural defects can occur because of local symmetry changes and electronic structure reconfiguration. An ionic crystal lattice with charged ion (or vacancy) injection typically undergoes an expansion due to the increased Coulomb repulsion between neighboring ions. , Therefore, we expect that a high density of lattice defects and a high degree of lattice distortions are associated with the accommodation of the excess charge. Indeed, it is evident that a high density of dislocations results in the formation of nanodomains, and the overall lattices of the treated ReS 2 are expanded as compared to that of pristine ReS 2 .…”

Se-Vacancy Healing with Substitutional Oxygen in WSe2 for High-Mobility p-Type Field-Effect Transistors

“…By comparing the atomic structures of the two samples (Figure d,e), it is confirmed that after the O-doping process, the WSe 2 lattice structure was well preserved without structure transition or modification, and no residuals remained on the surface after the etching process. However, it can be speculated that if oxygen atoms indeed substitute for Se vacancies, the doped WSe 2 lattice structure would be distorted due to the lattice-charge interplay causing the modification of the ionic bonding environment . To check whether the lattice is distorted, layerwise spacing for the out-of-plane direction was compared between the two samples (Figure f, left).…”