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Utilizing interlayer excitons in bilayer WS2 for increased photovoltaic response in ultrathin graphene vertical cross-bar photodetecting tunneling transistors
- Source :
- ACS Nano
- Publication Year :
- 2018
- Publisher :
- American Chemical Society, 2018.
-
Abstract
- Here we study the layer-dependent photoconductivity in Gr/WS2/Gr vertical stacked tunneling (VST) cross-bar devices made using two-dimensional (2D) materials all grown by chemical vapor deposition. The larger number of devices (>100) enables a statistically robust analysis on the comparative differences in the photovoltaic response of monolayer and bilayer WS2, which cannot be achieved in small batch devices made using mechanically exfoliated materials. We show a dramatic increase in photovoltaic response for Gr/WS2(2L)/Gr compared to monolayers because of the long inter- and intralayer exciton lifetimes and the small exciton binding energy (both interlayer and intralayer excitons) of bilayer WS2 compared with that of monolayer WS2. Different doping levels and dielectric environments of top and bottom graphene electrodes result in a potential difference across a ∼1 nm vertical device, which gives rise to large electric fields perpendicular to the WS2 layers that cause band structure modification. Our results show how precise control over layer number in all 2D VST devices dictates the photophysics and performance for photosensing applications.
- Subjects :
- Materials science
business.industry
Graphene
Photoconductivity
Exciton
Bilayer
General Engineering
General Physics and Astronomy
Heterojunction
02 engineering and technology
Dielectric
010402 general chemistry
021001 nanoscience & nanotechnology
7. Clean energy
01 natural sciences
0104 chemical sciences
law.invention
law
Monolayer
Optoelectronics
General Materials Science
0210 nano-technology
business
Quantum tunnelling
Subjects
Details
- Language :
- English
- Database :
- OpenAIRE
- Journal :
- ACS Nano
- Accession number :
- edsair.doi.dedup.....48805dae406ee204d57c5c4db33fb010