Engineering Point-Defect States in Monolayer WSe₂

Abstract

Defect engineering is a key approach for tailoring the properties of the emerging two-dimensional semiconductors. Here, we report an atomic engineering of the W vacancy in monolayer WSe 2 by single potassium atom decoration. The K decoration alters the energy states and reshapes the wave-function such that previously hidden mid-gap states become visible with well-resolved multiplets in scanning tunneling spectroscopy. Their energy levels are in good agreement with first principle calculations. More interestingly, the calculations show that an unpaired electron donated by the K atom can lead to a local magnetic moment, exhibiting an onoff switching by the odd-even number of electron filling. Experimentally the Fermi level is pinned above all defect states due to the graphite substrate, corresponding to an off state. The close agreement between theory and experiment in the off state, on the other hand, suggest a possibility of gate-programmable magnetic moments at the defects.

Molecular Functionalization of Chemically Active Defects in WSe2 for Enhanced Opto‐Electronics

“…Theoretical calculations reveal that from an energetic viewpoint, the energy required to form Se vacancies, exposed in the outer surface, is lower compared to the generation of vacancies of W, which are embedded in the underlying layer. [ 28,29 ] We infer that the defects observed in the STM image are most likely Se vacancies, and the simulated STM image showing the surface electron state of WSe 2 with 0.7% Se vacancy in Figure 1b further confirms our interpretation. The strong brightness difference between W and Se atoms indicates the electron rich nature in the Se sites on the crystal surface, and the missing of one bright dot refers to a Se vacancy site.…”

Universal mechanical exfoliation of large-area 2D crystals

“…T wo-dimensional (2D) materials continue to reveal dimensionality-correlated quantum phenomena [1][2][3][4][5][6] , such as 2D superconductivity, magnetism, topologically protected states, and quantum transport 1,[7][8][9][10][11] . Stacking 2D materials into van der Waals heterostructures leads to further emergent phenomena and derived device concepts 12,13 .…”

Sublattice Dependence and Gate Tunability of Midgap and Resonant States Induced by Native Dopants in Bernal-Stacked Bilayer Graphene

“…[8][9][10] Scanning tunneling microscopy (STM) investigations conducted on doped 2D semiconducting TMD have revealed their spatial configuration and their electronic structure at the atomic scale. [11][12][13][14][15] Bernal-stacked bilayer graphene (BLG) is also a semiconducting 2D material, particularly known for its unique tunable bandgap. [16][17][18] This unique property makes BLG especially promising for quantum information technology as it allows designing gate-defined confinement regions such as constrictions 19 or quantum dots.…”