Spatially Resolved Persistent Photoconductivity in MoS2-WS2 Lateral Heterostructures
Samuel Berweger1, Hanyu Zhang2, Prasana K Sahoo3,4
1Applied Physics Division, National Institute of Standards and Technology, Boulder, Colorado 80305, United States.
ACS Nano
|October 12, 2020
Summary
Photoconductivity in 2D semiconductors like MoS2-WS2 heterostructures is linked to optical absorption. Photogenerated carriers can persist for days, significantly increasing carrier density and altering material properties.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- 2D semiconductors exhibit strong coupling between optical and electronic properties.
- Understanding carrier dynamics in heterostructures is crucial for device applications.
Purpose of the Study:
- To investigate spatial variations in photoconductivity in MoS2-WS2 heterostructures.
- To elucidate the relationship between optical excitation, carrier generation, and material properties.
Main Methods:
- Near-field scanning microwave microscopy (SMM) with photon energy-resolved narrowband illumination.
- Finite element modeling.
- Photoluminescence (PL) mapping.
Main Results:
- Photoconductivity onset correlates with optical absorption, indicating exciton dissociation into free carriers.
- Photogenerated carriers (likely n-type) can persist for days, increasing carrier density up to 200-fold.
- Persistent photoconductivity is influenced by MoS2 domains and charge transfer across the heterostructure.
Conclusions:
- Optoelectronic responses in 2D heterostructures are complex and spatially dependent.
- Persistent photoconductivity can lead to metastable charged states, affecting measurements in the dark state.
- Charge transfer and exciton dissociation play significant roles in the optoelectronic behavior of MoS2-WS2 heterostructures.
Related Concept Videos
02:26Photoelectric Effect
37.7K
When light of a particular wavelength strikes a metal surface, electrons are emitted. This is called the photoelectric effect. The minimum frequency of light that can cause such emission of electrons is called the threshold frequency, which is specific to the metal. Light with a frequency lower than the threshold frequency, even if it is of high intensity, cannot initiate the emission of electrons. However, when the frequency is higher than the threshold value, the number of electrons ejected...
37.7K
01:25MOS Capacitor
1.3K
A Metal-Oxide-Semiconductor (MOS) capacitor is a fundamental structure used extensively in semiconductor device technology, particularly in the fabrication of integrated circuits and MOSFETs (metal-oxide-semiconductor field-effect transistors). The MOS capacitor consists of three layers: a metal gate, a dielectric oxide, and a semiconductor substrate.
The metal gate is typically made from highly conductive materials such as aluminum or polysilicon. Beneath the metal gate lies a thin layer of...
The metal gate is typically made from highly conductive materials such as aluminum or polysilicon. Beneath the metal gate lies a thin layer of...
1.3K