Highly dispersive molybdenum disulfide nanoflakes (MoS2 NFs), without any phase transition during the exfoliation process, are desirable for full utilization of their semiconductor properties in practical applications. Here, we demonstrate an innovate approach for fabricating MoS2 NFs by using hydrazine-assisted ball milling via the synergetic effect of chemical intercalation and mechanical exfoliation. The NFs obtained have a lateral size of 600–800 nm, a thickness less than 3 nm, and high crystallinity in the 2H semiconducting phase. They form a stable dispersion in various solvents, which will be helpful for many applications, due to the oxygen functional group. To investigate production of a two-dimensional (2D) photodetector, 2D semiconducting MoS2, MoS2–p-Si vertical devices were fabricated, and their optical properties were characterized. The photodiode exhibited consistent responses with excellent photo-switching characteristics with wavelengths of 850, 530, and 400 nm.
Artificial synapses based on 2D MoS2 memtransistors have recently attracted considerable attention as a promising device architecture for complex neuromorphic systems. However, previous memtransistor devices occasionally cause uncontrollable analog switching and unreliable synaptic plasticity due to random variations in the field‐induced defect migration. Herein, a highly reliable 2D MoS2/Nb2O5 heterostructure memtransistor device is demonstrated, in which the Nb2O5 interlayer thickness is a critical material parameter to induce and tune analog switching characteristics of the 2D MoS2. Ultraviolet photoelectron spectroscopy and photoluminescence analyses reveal that the Schottky barrier height at the 2D channel–electrode junction of the MoS2/Nb2O5 heterostructure films is increased, leading to more effective contact barrier modulation and allowing more reliable resistive switching. The 2D/oxide memtransistors attain dual‐terminal (drain and gate) stimulated heterosynaptic plasticity and highly precise multi‐states. In addition, the memtransistor devices show an extremely low power consumption of ≈6 pJ and reliable potentiation/depression endurance characteristics over 2000 pulses. A high pattern recognition accuracy of ≈94.2% is finally achieved from the synaptic plasticity modulated by the drain pulse configuration using an image pattern recognition simulation. Thus, the novel 2D/oxide memtransistor makes a potential neuromorphic circuitry more flexible and energy‐efficient, promoting the development of more advanced neuromorphic systems.
A growth technique
to directly prepare two-dimensional (2D) materials
onto conventional semiconductor substrates, enabling low-temperature,
high-throughput, and large-area capability, is needed to realize competitive
2D transition-metal dichalcogenide (TMD)/three-dimensional (3D) semiconductor
heterojunction devices. Therefore, we herein successfully developed
an atmospheric-pressure plasma-enhanced chemical vapor deposition
(AP-PECVD) technique, which could grow MoS2 and WS2 multilayers directly onto PET flexible substrate as well
as 4-in. Si substrates at temperatures of <200 °C. The as-fabricated
MoS2/Si and WS2/Si heterojunctions exhibited
large and fast photocurrent responses under illumination of a green
light. The measured photocurrent was linearly proportional to the
laser power, indicating that trapping and detrapping of the photogenerated
carriers at defect states could not significantly suppress the collection
of photocarriers. All the results demonstrated that our AP-PECVD method
could produce high-quality TMD/Si 2D–3D heterojunctions for
optoelectronic applications.
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