Atomic Visualization of the 3D Charge Density Wave Stacking in 1T-TaS2 by Cryogenic Transmission Electron Microscopy.

Charge density waves (CDWs) in 1T-TaS2 maintain 2D ordering by forming periodic in-plane star-of-David (SOD) patterns, while they also intertwined with orbital order in the c axis. Recent theoretical calculations and surface measurements have explored 3D CDW configurations, but interlayer intertwining of a 2D CDW order remains elusive. Here, we investigate the in- and out-of-plane ordering of the commensurate CDW superstructure in a 1T-TaS2 thin flake in real space, using aberration-corrected cryogenic transmission electronic microscopy (cryo-TEM) in low-dose mode, far below the threshold dose for an electron-induced CDW phase transition. By scrutinizing the phase intensity variation of modulated Ta atoms, we visualize the penetrative 3D CDW stacking structure, revealing an intertwining multidomain structure with three types of vertical CDW stacking configurations. Our results provide microstructural evidence for the coexistence of local Mott insulation and metal phases and offer a paradigm for studying the CDW structure and correlation order in condensed-matter physics using cryo-TEM.

Engineering the Crack Structure and Fracture Behavior in Monolayer MoS2 By Selective Creation of Point Defects.

Monolayer transition-metal dichalcogenides, e.g., MoS2 , typically have high intrinsic strength and Young's modulus, but low fracture toughness. Under high stress, brittle fracture occurs followed by cleavage along a preferential lattice direction, leading to catastrophic failure. Defects have been reported to modulate the fracture behavior, but pertinent atomic mechanism still remains elusive. Here, sulfur (S) and MoSn point defects are selectively created in monolayer MoS2 using helium- and gallium-ion-beam lithography, both of which reduce the stiffness of the monolayer, but enhance its fracture toughness. By monitoring the atomic structure of the cracks before and after the loading fracture, distinct atomic structures of the cracks and fracture behaviors are found in the two types of defect-containing monolayer MoS2 . Combined with molecular dynamics simulations, the key role of individual S and MoSn point defects is identified in the fracture process and the origin of the enhanced fracture toughness is elucidated. It is a synergistic effect of defect-induced deflection and bifurcation of cracks that enhance the energy release rate, and the formation of widen crack tip when fusing with point defects that prevents the crack propagation. The findings of this study provide insights into defect engineering and flexible device applications of monolayer MoS2 .

[The Comparison between Automatic Potentiometry and Oxidation-reduction Titration Method in Determining Easily Oxidized Substances in Infusion Sets for Single Use].

Objective: To compare the automatic potentiometry and oxidation-reduction titration methods in determining easily oxidized substances in infusion sets for single use. Methods: The easily oxidized substances in infusion sets for single use were determined using two methods. The precise test and the Student's test were be carried out. Results: Both of the methods could satisfy the analytic demand. The relative standard deviation of automatic potentiometry is 0.06%; the relative standard deviation of oxidation-reduction titration method is 0.07%; when α was 0.05, P value was 0.92. There was no statistically significant difference between the two methods. Conclusion: Automatic potentiometry method can substitute oxidation-reduction titration methods.