2 research outputs found
Electrical Characterization of Discrete Defects and Impact of Defect Density on Photoluminescence in Monolayer WS<sub>2</sub>
Transition-metal
dichalcogenides (TMDs) are an exciting class of
2D materials that exhibit many promising electronic and optoelectronic
properties with potential for future device applications. The properties
of TMDs are expected to be strongly influenced by a variety of defects
which result from growth procedures and/or fabrication. Despite the
importance of understanding defect-related phenomena, there remains
a need for quantitative nanometer-scale characterization of defects
over large areas in order to understand the relationship between defects
and observed properties, such as photoluminescence (PL) and electrical
conductivity. In this work, we present conductive atomic force microscopy
measurements which reveal nanometer-scale electronically active defects
in chemical vapor deposition-grown WS<sub>2</sub> monolayers with
defect density varying from 2.3 × 10<sup>10</sup> cm<sup>–2</sup> to 4.5 × 10<sup>11</sup> cm<sup>–2</sup>. Comparing
these defect density measurements with PL measurements across large
areas (>20 μm distances) reveals a strong inverse relationship
between WS<sub>2</sub> PL intensity and defect density. We propose
a model in which the observed electronically active defects serve
as nonradiative recombination centers and obtain good agreement between
the experiments and model
Magnetic Field-Induced Spin Nematic Phase Up to Room Temperature in Epitaxial Antiferromagnetic FeTe Thin Films Grown by Molecular Beam Epitaxy
Electronic nematicity, where strong correlations drive
electrons
to align in a way that lowers the crystal symmetry, is ubiquitous
among unconventional superconductors. Understanding the interplay
of such a nematic state with other electronic phases underpins the
complex behavior of these materials and the potential for tuning their
properties through external stimuli. Here, we report magnetic field-induced
spin nematicity in a model system tetragonal FeTe, the parent compound
of iron chalcogenide superconductors, which exhibits a bicollinear
antiferromagnetic order. The studies were conducted on epitaxial FeTe
thin films grown on SrTiO3(001) substrates by molecular
beam epitaxy, where the bicollinear antiferromagnetic order was confirmed
by in situ atomic resolution scanning tunneling microscopy
imaging. A 2-fold anisotropy is observed in in-plane angle-dependent
magnetoresistance measurements, indicative of magnetic field-induced
nematicity. Such 2-fold anisotropy persists up to 300 K, well-above
the bicollinear antiferromagnetic ordering temperature of 75 K, indicating
a magnetic field-induced spin nematic phase up to room temperature
in the antiferromagnet FeTe