Mechanisms of photoconductivity in atomically thin MoS2

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Atomically thin transition metal dichalcogenides are promising for sensitive photodetection.
• Molybdenum disulfide (MoS2) is a key material in this field.

Purpose of the Study:

• Investigate the photoconductivity of mono- and bilayer molybdenum disulfide field-effect transistors.
• Identify and characterize photovoltaic and photoconductive effects in MoS2 photodetectors.

Main Methods:

• Fabrication and electrical characterization of biased MoS2 field-effect transistors.
• Measurement of photocurrent and photovoltage under varying optical power and gate voltage.
• Development of a model to explain observed phenomena.

Main Results:

• Observed both photovoltaic and photoconductive effects, both exhibiting significant photogain.
• Photovoltaic effect linked to charge transfer to surface molecules (e.g., water on SiO2).
• Photoconductive effect attributed to carrier trapping in MoS2 band tail states.

Conclusions:

• A model successfully reproduces experimental observations of MoS2 photodetectors.
• Findings provide design and engineering strategies for MoS2-based photodetectors.
• Results are potentially generalizable to other transition metal dichalcogenides.