Leaflet geometry extraction and parametric representation of a pericardial artificial heart valve

Peer reviewed: YesNRC publication: Ye

Fabrication of [001]-Oriented Tungsten Tips for High Resolution Scanning Tunneling Microscopy

The structure of the [001]-oriented single crystalline tungsten probes sharpened in ultra-high vacuum using electron beam heating and ion sputtering has been studied using scanning and transmission electron microscopy. The electron microscopy data prove reproducible fabrication of the single-apex tips with nanoscale pyramids grained by the {011} planes at the apexes. These sharp, [001]-oriented tungsten tips have been successfully utilized in high resolution scanning tunneling microscopy imaging of HOPG(0001), SiC(001) and graphene/SiC(001) surfaces. The electron microscopy characterization performed before and after the high resolution STM experiments provides direct correlation between the tip structure and picoscale spatial resolution achieved in the experiments

Nontrivial evolution of the Sb(111) electronic and atomic structure after ion irradiation

Defects in crystal structure of layered material can modify the surface states. Ion bombardment is a simple way to introduce defects into a crystal lattice in the surface region. Comprehensive scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and photoemission studies are presented to uncover the impact of ion etching and thermal annealing on the atomic and electronic structure of Sb (1 1 1) surface. We reveal the unusual behavior of the Sb(1 1 1) surface after Ar+ sputtering at 300 K (RT). The 3 nm-sized terraces formed even after a prolonged ion bombardment are established by LEED. Also, an increase in density of states (DOS) at the Fermi edge is detected for the etched Sb(1 1 1) surface due to the ruptured covalent bonds (CBs). (C) 2018 Elsevier B.V. All rights reserved

The topological soliton in Peierls semimetal Sb

Abstract Sb is a three-dimensional Peierls insulator. The Peierls instability gives rise to doubling of the translational period along the [111] direction and alternating van der Waals and covalent bonding between (111) atomic planes. At the (111) surface of Sb, the Peierls condition is violated, which in theory can give rise to properties differing from the bulk. The atomic and electronic structure of the (111) surface of Sb have been simulated by density functional theory calculations. We have considered the two possible (111) surfaces, containing van der Waals dangling bonds or containing covalent dangling bonds. In the models, the surfaces are infinite and the structure is defect free. Structural optimization of the model containing covalent dangling bonds results in strong deformation, which is well described by a topological soliton within the Su–Schrieffer–Heeger model centered about 25 Å below the surface. The electronic states associated with the soliton see an increase in the density of states (DOS) at the Fermi level by around an order of magnitude at the soliton center. Scanning tunneling microscopy and spectroscopy (STM/STS) measurements reveal two distinct surface regions, indicating that there are different surface regions cleaving van der Waals and covalent bonds. The DFT is in good agreement with the STM/STS experiments