2 research outputs found
Double-Floating-Gate van der Waals Transistor for High-Precision Synaptic Operations
Two-dimensional
materials and their heterostructures
have thus
far been identified as leading candidates for nanoelectronics owing
to the near-atom thickness, superior electrostatic control, and adjustable
device architecture. These characteristics are indeed advantageous
for neuro-inspired computing hardware where precise programming is
strongly required. However, its successful demonstration fully utilizing
all of the given benefits remains to be further developed. Herein,
we present van der Waals (vdW) integrated synaptic transistors with
multistacked floating gates, which are reconfigured upon surface oxidation.
When compared with a conventional device structure with a single floating
gate, our double-floating-gate (DFG) device exhibits better nonvolatile
memory performance, including a large memory window (>100 V), high
on–off current ratio (∼107), relatively long
retention time (>5000 s), and satisfactory cyclic endurance (>500
cycles), all of which can be attributed to its increased charge-storage
capacity and spatial redistribution. This facilitates highly effective
modulation of trapped charge density with a large dynamic range. Consequently,
the DFG transistor exhibits an improved weight update profile in long-term
potentiation/depression synaptic behavior for nearly ideal classification
accuracies of up to 96.12% (MNIST) and 81.68% (Fashion-MNIST). Our
work adds a powerful option to vdW-bonded device structures for highly
efficient neuromorphic computing
Characterization of Rotational Stacking Layers in Large-Area MoSe<sub>2</sub> Film Grown by Molecular Beam Epitaxy and Interaction with Photon
Transition metal
dichalcogenides (TMDCs) are promising next-generation
materials for optoelectronic devices because, at subnanometer thicknesses,
they have a transparency, flexibility, and band gap in the near-infrared
to visible light range. In this study, we examined continuous, large-area
MoSe<sub>2</sub> film, grown by molecular beam epitaxy on an amorphous
SiO<sub>2</sub>/Si substrate, which facilitated direct device fabrication
without exfoliation. Spectroscopic measurements were implemented to
verify the formation of a homogeneous MoSe<sub>2</sub> film by performing
mapping on the micrometer scale and measurements at multiple positions.
The crystalline structure of the film showed hexagonal (2H) rotationally
stacked layers. The local strain at the grain boundaries was mapped
using a geometric phase analysis, which showed a higher strain for
a 30° twist angle compared to a 13° angle. Furthermore,
the photon–matter interaction for the rotational stacking structures
was investigated as a function of the number of layers using spectroscopic
ellipsometry. The optical band gap for the grown MoSe<sub>2</sub> was
in the near-infrared range, 1.24–1.39 eV. As the film thickness
increased, the band gap energy decreased. The atomically controlled
thin MoSe<sub>2</sub> showed promise for application to nanoelectronics,
photodetectors, light emitting diodes, and valleytronics